[3/4] iio: adc: add a driver for the SAR ADC found in Amlogic Meson SoCs

Commit Message

Martin Blumenstingl Jan. 11, 2017, 5:43 p.m. UTC

This adds support for the SAR (Successive Approximation Register) ADC
on the Amlogic Meson SoCs.

The code is based on the public S805 (Meson8b) and S905 (GXBB)
datasheets, as well as by reading (various versions of) the vendor
driver and by inspecting the registers on the vendor kernels of my
testing-hardware.

Currently the GXBB, GXL and GXM SoCs are supported. GXBB hardware has
10-bit ADC resolution, while GXL and GXM have 12-bit ADC resolution.
The code was written to support older SoCs (Meson8 and Meson8b) as well,
but due to lack of actual testing-hardware no of_device_id was added for
these.

Two "features" from the vendor driver are currently missing:
- the vendor driver uses channel #7 for calibration (this improves the
  accuracy of the results - in my tests the results were less than 3%
  off without calibration compared to the vendor driver). Adding support
  for this should be easy, but is not required for most applications.
- channel #6 is connected to the SoCs internal temperature sensor.
  Adding support for this is probably not so easy since (based on the
  u-boot sources) most SoC versions are using different registers and
  algorithms for the conversion from "ADC value" to temperature.

Supported by the hardware but currently not supported by the driver:
- reading multiple channels at the same time (the hardware has a FIFO
  buffer which stores multiple results)
- continuous sampling (this would require a way to enable this
  individually because otherwise the ADC would be drawing power
  constantly)
- interrupt support (similar to the vendor driver this new driver is
  polling the results. It is unclear if the IRQ-mode is supported on
  older (Meson6 or Meson8) hardware as well or if there are any errata)

Signed-off-by: Martin Blumenstingl <[e-mail]>
---
 drivers/iio/adc/Kconfig        |  12 +
 drivers/iio/adc/Makefile       |   1 +
 drivers/iio/adc/meson_saradc.c | 860 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 873 insertions(+)
 create mode 100644 drivers/iio/adc/meson_saradc.c

Comments

Jonathan Cameron Jan. 14, 2017, 2:46 p.m. UTC | #1

On 11/01/17 17:43, Martin Blumenstingl wrote:
> This adds support for the SAR (Successive Approximation Register) ADC
> on the Amlogic Meson SoCs.
> 
> The code is based on the public S805 (Meson8b) and S905 (GXBB)
> datasheets, as well as by reading (various versions of) the vendor
> driver and by inspecting the registers on the vendor kernels of my
> testing-hardware.
> 
> Currently the GXBB, GXL and GXM SoCs are supported. GXBB hardware has
> 10-bit ADC resolution, while GXL and GXM have 12-bit ADC resolution.
> The code was written to support older SoCs (Meson8 and Meson8b) as well,
> but due to lack of actual testing-hardware no of_device_id was added for
> these.
> 
> Two "features" from the vendor driver are currently missing:
> - the vendor driver uses channel #7 for calibration (this improves the
>   accuracy of the results - in my tests the results were less than 3%
>   off without calibration compared to the vendor driver). Adding support
>   for this should be easy, but is not required for most applications.
> - channel #6 is connected to the SoCs internal temperature sensor.
>   Adding support for this is probably not so easy since (based on the
>   u-boot sources) most SoC versions are using different registers and
>   algorithms for the conversion from "ADC value" to temperature.
> 
> Supported by the hardware but currently not supported by the driver:
> - reading multiple channels at the same time (the hardware has a FIFO
>   buffer which stores multiple results)
> - continuous sampling (this would require a way to enable this
>   individually because otherwise the ADC would be drawing power
>   constantly)
> - interrupt support (similar to the vendor driver this new driver is
>   polling the results. It is unclear if the IRQ-mode is supported on
>   older (Meson6 or Meson8) hardware as well or if there are any errata)
>
Russell Cc'd for a quick question on the clk api.

Ideally include a source for datasheets if available. Saves time googling and
perhaps getting the wrong thing!

A few other minor comments inline. Pretty good V1.

Jonathan
> Signed-off-by: Martin Blumenstingl <[e-mail]>
> ---
>  drivers/iio/adc/Kconfig        |  12 +
>  drivers/iio/adc/Makefile       |   1 +
>  drivers/iio/adc/meson_saradc.c | 860 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 873 insertions(+)
>  create mode 100644 drivers/iio/adc/meson_saradc.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 9c8b558ba19e..86059b9b91bf 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -371,6 +371,18 @@ config MEN_Z188_ADC
>  	  This driver can also be built as a module. If so, the module will be
>  	  called men_z188_adc.
>  
> +config MESON_SARADC
> +	tristate "Amlogic Meson SAR ADC driver"
> +	default ARCH_MESON
> +	depends on OF && COMMON_CLK && (ARCH_MESON || COMPILE_TEST)
> +	select REGMAP_MMIO
> +	help
> +	  Say yes here to build support for the SAR ADC found in Amlogic Meson
> +	  SoCs.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called meson_saradc.
> +
>  config MXS_LRADC
>          tristate "Freescale i.MX23/i.MX28 LRADC"
>          depends on (ARCH_MXS || COMPILE_TEST) && HAS_IOMEM
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index d36c4be8d1fc..de05b9e75f8f 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -36,6 +36,7 @@ obj-$(CONFIG_MCP320X) += mcp320x.o
>  obj-$(CONFIG_MCP3422) += mcp3422.o
>  obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
>  obj-$(CONFIG_MEN_Z188_ADC) += men_z188_adc.o
> +obj-$(CONFIG_MESON_SARADC) += meson_saradc.o
>  obj-$(CONFIG_MXS_LRADC) += mxs-lradc.o
>  obj-$(CONFIG_NAU7802) += nau7802.o
>  obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
> new file mode 100644
> index 000000000000..06e8ac620385
> --- /dev/null
> +++ b/drivers/iio/adc/meson_saradc.c
> @@ -0,0 +1,860 @@
> +/*
> + * Amlogic Meson Successive Approximation Register (SAR) A/D Converter
> + *
> + * Copyright (C) 2017 Martin Blumenstingl <[e-mail]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/clk-provider.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/iio/iio.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/clk.h>
> +#include <linux/completion.h>
> +#include <linux/delay.h>
> +#include <linux/reset.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +
> +#define SAR_ADC_REG0						0x00
> +	#define SAR_ADC_REG0_PANEL_DETECT			BIT(31)
> +	#define SAR_ADC_REG0_BUSY_MASK				GENMASK(30, 28)
> +	#define SAR_ADC_REG0_DELTA_BUSY				BIT(30)
> +	#define SAR_ADC_REG0_AVG_BUSY				BIT(29)
> +	#define SAR_ADC_REG0_SAMPLE_BUSY			BIT(28)
> +	#define SAR_ADC_REG0_FIFO_FULL				BIT(27)
> +	#define SAR_ADC_REG0_FIFO_EMPTY				BIT(26)
> +	#define SAR_ADC_REG0_FIFO_COUNT_MASK			GENMASK(25, 21)
> +	#define SAR_ADC_REG0_ADC_BIAS_CTRL_MASK			GENMASK(20, 19)
> +	#define SAR_ADC_REG0_CURR_CHAN_ID_MASK			GENMASK(18, 16)
> +	#define SAR_ADC_REG0_ADC_TEMP_SEN_SEL			BIT(15)
> +	#define SAR_ADC_REG0_SAMPLING_STOP			BIT(14)
> +	#define SAR_ADC_REG0_CHAN_DELTA_EN_MASK			GENMASK(13, 12)
> +	#define SAR_ADC_REG0_DETECT_IRQ_POL			BIT(10)
> +	#define SAR_ADC_REG0_DETECT_IRQ_EN			BIT(9)
> +	#define SAR_ADC_REG0_FIFO_CNT_IRQ_MASK			GENMASK(8, 4)
> +	#define SAR_ADC_REG0_FIFO_IRQ_EN			BIT(3)
> +	#define SAR_ADC_REG0_SAMPLING_START			BIT(2)
> +	#define SAR_ADC_REG0_CONTINUOUS_EN			BIT(1)
> +	#define SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE		BIT(0)
> +
> +#define SAR_ADC_CHAN_LIST					0x04
> +	#define SAR_ADC_CHAN_LIST_MAX_INDEX_MASK		GENMASK(26, 24)
> +	#define SAR_ADC_CHAN_CHAN_ENTRY_MASK(_chan)		\
> +					(GENMASK(2, 0) << (_chan * 3))
> +
> +#define SAR_ADC_AVG_CNTL					0x08
> +	#define SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(_chan)		\
> +					(16 + (_chan * 2))
> +	#define SAR_ADC_AVG_CNTL_AVG_MODE_MASK(_chan)		\
> +					(GENMASK(17, 16) << (_chan * 2))
> +	#define SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(_chan)	\
> +					(0 + (_chan * 2))
> +	#define SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(_chan)	\
> +					(GENMASK(1, 0) << (_chan * 2))
> +
> +#define SAR_ADC_REG3						0x0c
> +	#define SAR_ADC_REG3_CNTL_USE_SC_DLY			BIT(31)
> +	#define SAR_ADC_REG3_CLK_EN				BIT(30)
> +	#define SAR_ADC_REG3_BL30_INITIALIZED			BIT(28)
> +	#define SAR_ADC_REG3_CTRL_CONT_RING_COUNTER_EN		BIT(27)
> +	#define SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE		BIT(26)
> +	#define SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK		GENMASK(25, 23)
> +	#define SAR_ADC_REG3_DETECT_EN				BIT(22)
> +	#define SAR_ADC_REG3_ADC_EN				BIT(21)
> +	#define SAR_ADC_REG3_PANEL_DETECT_COUNT_MASK		GENMASK(20, 18)
> +	#define SAR_ADC_REG3_PANEL_DETECT_FILTER_TB_MASK	GENMASK(17, 16)
> +	#define SAR_ADC_REG3_ADC_CLK_DIV_SHIFT			10
> +	#define SAR_ADC_REG3_ADC_CLK_DIV_WIDTH			5
> +	#define SAR_ADC_REG3_ADC_CLK_DIV_MASK			GENMASK(15, 10)
> +	#define SAR_ADC_REG3_BLOCK_DLY_SEL_MASK			GENMASK(9, 8)
> +	#define SAR_ADC_REG3_BLOCK_DLY_MASK			GENMASK(7, 0)
> +
> +#define SAR_ADC_DELAY						0x10
> +	#define SAR_ADC_DELAY_INPUT_DLY_SEL_MASK		GENMASK(25, 24)
> +	#define SAR_ADC_DELAY_BL30_BUSY				BIT(15)
> +	#define SAR_ADC_DELAY_KERNEL_BUSY			BIT(14)
> +	#define SAR_ADC_DELAY_INPUT_DLY_CNT_MASK		GENMASK(23, 16)
> +	#define SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK		GENMASK(9, 8)
> +	#define SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK		GENMASK(7, 0)
> +
> +#define SAR_ADC_LAST_RD						0x14
> +	#define SAR_ADC_LAST_RD_LAST_CHANNEL1_MASK		GENMASK(23, 16)
> +	#define SAR_ADC_LAST_RD_LAST_CHANNEL0_MASK		GENMASK(9, 0)
> +
> +#define SAR_ADC_FIFO_RD						0x18
> +	#define SAR_ADC_FIFO_RD_CHAN_ID_MASK			GENMASK(14, 12)
> +	#define SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK		GENMASK(11, 0)
> +
> +#define SAR_ADC_AUX_SW						0x1c
> +	#define SAR_ADC_AUX_SW_MUX_SEL_CHAN_MASK(_chan)		\
> +					(GENMASK(10, 8) << ((_chan - 2) * 2))
> +	#define SAR_ADC_AUX_SW_VREF_P_MUX			BIT(6)
> +	#define SAR_ADC_AUX_SW_VREF_N_MUX			BIT(5)
> +	#define SAR_ADC_AUX_SW_MODE_SEL				BIT(4)
> +	#define SAR_ADC_AUX_SW_YP_DRIVE_SW			BIT(3)
> +	#define SAR_ADC_AUX_SW_XP_DRIVE_SW			BIT(2)
> +	#define SAR_ADC_AUX_SW_YM_DRIVE_SW			BIT(1)
> +	#define SAR_ADC_AUX_SW_XM_DRIVE_SW			BIT(0)
> +
> +#define SAR_ADC_CHAN_10_SW					0x20
> +	#define SAR_ADC_CHAN_10_SW_CHAN1_MUX_SEL_MASK		GENMASK(25, 23)
> +	#define SAR_ADC_CHAN_10_SW_CHAN1_VREF_P_MUX		BIT(22)
> +	#define SAR_ADC_CHAN_10_SW_CHAN1_VREF_N_MUX		BIT(21)
> +	#define SAR_ADC_CHAN_10_SW_CHAN1_MODE_SEL		BIT(20)
> +	#define SAR_ADC_CHAN_10_SW_CHAN1_YP_DRIVE_SW		BIT(19)
> +	#define SAR_ADC_CHAN_10_SW_CHAN1_XP_DRIVE_SW		BIT(18)
> +	#define SAR_ADC_CHAN_10_SW_CHAN1_YM_DRIVE_SW		BIT(17)
> +	#define SAR_ADC_CHAN_10_SW_CHAN1_XM_DRIVE_SW		BIT(16)
> +	#define SAR_ADC_CHAN_10_SW_CHAN0_MUX_SEL_MASK		GENMASK(9, 7)
> +	#define SAR_ADC_CHAN_10_SW_CHAN0_VREF_P_MUX		BIT(6)
> +	#define SAR_ADC_CHAN_10_SW_CHAN0_VREF_N_MUX		BIT(5)
> +	#define SAR_ADC_CHAN_10_SW_CHAN0_MODE_SEL		BIT(4)
> +	#define SAR_ADC_CHAN_10_SW_CHAN0_YP_DRIVE_SW		BIT(3)
> +	#define SAR_ADC_CHAN_10_SW_CHAN0_XP_DRIVE_SW		BIT(2)
> +	#define SAR_ADC_CHAN_10_SW_CHAN0_YM_DRIVE_SW		BIT(1)
> +	#define SAR_ADC_CHAN_10_SW_CHAN0_XM_DRIVE_SW		BIT(0)
> +
> +#define SAR_ADC_DETECT_IDLE_SW					0x24
> +	#define SAR_ADC_DETECT_IDLE_SW_DETECT_SW_EN		BIT(26)
> +	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK	GENMASK(25, 23)
> +	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_VREF_P_MUX	BIT(22)
> +	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_VREF_N_MUX	BIT(21)
> +	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_SEL		BIT(20)
> +	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_YP_DRIVE_SW	BIT(19)
> +	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_XP_DRIVE_SW	BIT(18)
> +	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_YM_DRIVE_SW	BIT(17)
> +	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_XM_DRIVE_SW	BIT(16)
> +	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK	GENMASK(9, 7)
> +	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_VREF_P_MUX	BIT(6)
> +	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_VREF_N_MUX	BIT(5)
> +	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_SEL		BIT(4)
> +	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_YP_DRIVE_SW	BIT(3)
> +	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_XP_DRIVE_SW	BIT(2)
> +	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_YM_DRIVE_SW	BIT(1)
> +	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_XM_DRIVE_SW	BIT(0)
> +
> +#define SAR_ADC_DELTA_10					0x28
> +	#define SAR_ADC_DELTA_10_TEMP_SEL			BIT(27)
> +	#define SAR_ADC_DELTA_10_TS_REVE1			BIT(26)
> +	#define SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_SHIFT	16
> +	#define SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_MASK		GENMASK(25, 16)
> +	#define SAR_ADC_DELTA_10_TS_REVE0			BIT(15)
> +	#define SAR_ADC_DELTA_10_TS_C_SHIFT			11
> +	#define SAR_ADC_DELTA_10_TS_C_MASK			GENMASK(14, 11)
> +	#define SAR_ADC_DELTA_10_TS_VBG_EN			BIT(10)
> +	#define SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_SHIFT	0
> +	#define SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_MASK		GENMASK(9, 0)
> +
> +/* NOTE: registers from here are undocumented (the vendor Linux kernel driver
> + * and u-boot source served as reference). These only seem to be relevant on
> + * GXBB and newer.
> + */
> +#define SAR_ADC_REG11						0x2c
> +	#define SAR_ADC_REG11_BANDGAP_EN			BIT(13)
> +
> +#define SAR_ADC_REG13						0x34
> +	#define SAR_ADC_REG13_12BIT_CALIBRATION_MASK		GENMASK(13, 8)
> +
> +#define SAR_ADC_MAX_FIFO_SIZE		32
> +#define SAR_ADC_NUM_CHANNELS		ARRAY_SIZE(meson_saradc_iio_channels)
> +#define SAR_ADC_VALUE_MASK(_priv)	(BIT(_priv->resolution) - 1)
> +
> +#define MESON_SAR_ADC_CHAN(_chan, _type) {				\
> +	.type = _type,							\
> +	.indexed = true,						\
> +	.channel = _chan,						\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
> +				BIT(IIO_CHAN_INFO_AVERAGE_RAW),		\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
> +	.datasheet_name = "SAR_ADC_CH"#_chan,				\
> +}
> +
> +/* TODO: the hardware supports IIO_TEMP for channel 6 as well which is
Multline comment syntax.
> + * currently not supported by this driver.
> + */
> +static const struct iio_chan_spec meson_saradc_iio_channels[] = {
> +	MESON_SAR_ADC_CHAN(0, IIO_VOLTAGE),
> +	MESON_SAR_ADC_CHAN(1, IIO_VOLTAGE),
> +	MESON_SAR_ADC_CHAN(2, IIO_VOLTAGE),
> +	MESON_SAR_ADC_CHAN(3, IIO_VOLTAGE),
> +	MESON_SAR_ADC_CHAN(4, IIO_VOLTAGE),
> +	MESON_SAR_ADC_CHAN(5, IIO_VOLTAGE),
> +	MESON_SAR_ADC_CHAN(6, IIO_VOLTAGE),
> +	MESON_SAR_ADC_CHAN(7, IIO_VOLTAGE),
> +	IIO_CHAN_SOFT_TIMESTAMP(8),
> +};
> +
> +enum meson_saradc_avg_mode {
> +	NO_AVERAGING = 0x0,
> +	MEAN_AVERAGING = 0x1,
> +	MEDIAN_AVERAGING = 0x2,
> +};
> +
> +enum meson_saradc_num_samples {
> +	ONE_SAMPLE = 0x0,
> +	TWO_SAMPLES = 0x1,
> +	FOUR_SAMPLES = 0x2,
> +	EIGHT_SAMPLES = 0x3,
> +};
> +
> +enum meson_saradc_chan7_mux_sel {
> +	CHAN7_MUX_VSS = 0x0,
> +	CHAN7_MUX_VDD_DIV4 = 0x1,
> +	CHAN7_MUX_VDD_DIV2 = 0x2,
> +	CHAN7_MUX_VDD_MUL3_DIV4 = 0x3,
> +	CHAN7_MUX_VDD = 0x4,
> +	CHAN7_MUX_CH7_INPUT = 0x7,
> +};
> +
> +struct meson_saradc_priv {
> +	struct regmap			*regmap;
> +	struct clk			*clkin;
> +	struct clk			*core_clk;
> +	struct clk			*sana_clk;
> +	struct clk			*adc_sel_clk;
> +	struct clk			*adc_clk;
> +	struct clk_gate			clk_gate;
> +	struct clk			*adc_div_clk;
> +	struct clk_divider		clk_div;
> +	struct regulator		*vref;
> +	struct completion		completion;
> +	u8				resolution;
> +};
> +
> +static const struct regmap_config meson_saradc_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 32,
> +	.reg_stride = 4,
> +	.max_register = SAR_ADC_REG13,
> +};
> +
> +static unsigned int meson_saradc_get_fifo_count(struct iio_dev *indio_dev)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	u32 regval;
> +
> +	regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
> +
> +	return FIELD_GET(SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
> +}
> +
> +static int meson_saradc_wait_busy_clear(struct iio_dev *indio_dev)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	int regval, timeout = 10000;
> +
> +	do {
> +		udelay(1);
> +		regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
> +	} while (FIELD_GET(SAR_ADC_REG0_BUSY_MASK, regval) && timeout--);
> +
> +	if (timeout < 0)
> +		return -ETIMEDOUT;
> +
> +	return 0;
> +}
> +
> +static int meson_saradc_read_raw_sample(struct iio_dev *indio_dev,
> +					const struct iio_chan_spec *chan,
> +					int *val)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	int ret, regval, fifo_chan, fifo_val, sum = 0, count = 0;
> +
> +	ret = meson_saradc_wait_busy_clear(indio_dev);
> +	if (ret)
> +		return ret;
> +
> +	regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
> +
> +	while (meson_saradc_get_fifo_count(indio_dev) > 0 &&
> +	       count < SAR_ADC_MAX_FIFO_SIZE) {
> +		regmap_read(priv->regmap, SAR_ADC_FIFO_RD, &regval);
> +
> +		fifo_chan = FIELD_GET(SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
> +		if (fifo_chan == chan->channel) {
> +			fifo_val = FIELD_GET(SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK,
> +					     regval) & SAR_ADC_VALUE_MASK(priv);
> +			sum += fifo_val;
> +			count++;
> +		}
> +	}
> +
> +	if (!count)
> +		return -ENOENT;
> +
> +	*val = sum / count;
> +
> +	return 0;
> +}
> +
> +static void meson_saradc_set_averaging(struct iio_dev *indio_dev,
> +				       const struct iio_chan_spec *chan,
> +				       enum meson_saradc_avg_mode mode,
> +				       enum meson_saradc_num_samples samples)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	u32 val;
> +
> +	val = samples << SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(chan->channel);
> +	regmap_update_bits(priv->regmap, SAR_ADC_AVG_CNTL,
> +			   SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(chan->channel),
> +			   val);
> +
> +	val = mode << SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(chan->channel);
> +	regmap_update_bits(priv->regmap, SAR_ADC_AVG_CNTL,
> +			   SAR_ADC_AVG_CNTL_AVG_MODE_MASK(chan->channel), val);
> +}
> +
> +static void meson_saradc_enable_channel(struct iio_dev *indio_dev,
> +					const struct iio_chan_spec *chan)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	u32 regval;
> +
> +	/* the SAR ADC engine allows sampling multiple channels at the same
> +	 * time. to keep it simple we're only working with one *internal*
> +	 * channel, which starts counting at index 0 (which means: count = 1).
> +	 */
> +	regval = FIELD_PREP(SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, 0);
> +	regmap_update_bits(priv->regmap, SAR_ADC_CHAN_LIST,
> +			   SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, regval);
> +
> +	/* map channel index 0 to the channel which we want to read */
> +	regval = FIELD_PREP(SAR_ADC_CHAN_CHAN_ENTRY_MASK(0), chan->channel);
> +	regmap_update_bits(priv->regmap, SAR_ADC_CHAN_LIST,
> +			   SAR_ADC_CHAN_CHAN_ENTRY_MASK(0), regval);
> +
> +	regval = FIELD_PREP(SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK,
> +			    chan->channel);
> +	regmap_update_bits(priv->regmap, SAR_ADC_DETECT_IDLE_SW,
> +			   SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK,
> +			   regval);
> +
> +	regval = FIELD_PREP(SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK,
> +			    chan->channel);
> +	regmap_update_bits(priv->regmap, SAR_ADC_DETECT_IDLE_SW,
> +			   SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK,
> +			   regval);
> +
> +	if (chan->channel == 6)
> +		regmap_update_bits(priv->regmap, SAR_ADC_DELTA_10,
> +				   SAR_ADC_DELTA_10_TEMP_SEL, 0);
> +}
> +
> +static void meson_saradc_set_channel7_mux(struct iio_dev *indio_dev,
> +					  enum meson_saradc_chan7_mux_sel sel)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	u32 regval;
> +
> +	regval = FIELD_PREP(SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, sel);
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG3,
> +			   SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, regval);
> +
> +	usleep_range(10, 20);
> +}
> +
> +static void meson_saradc_start_sample_engine(struct iio_dev *indio_dev)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
> +			   SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE,
> +			   SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE);
> +
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
> +			   SAR_ADC_REG0_SAMPLING_START,
> +			   SAR_ADC_REG0_SAMPLING_START);
> +}
> +
> +static void meson_saradc_stop_sample_engine(struct iio_dev *indio_dev)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
> +			   SAR_ADC_REG0_SAMPLING_STOP,
> +			   SAR_ADC_REG0_SAMPLING_STOP);
> +
> +	/* wait until all modules are stopped */
> +	meson_saradc_wait_busy_clear(indio_dev);
> +
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
> +			   SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE, 0);
> +}
> +
> +static void meson_saradc_lock(struct iio_dev *indio_dev)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	int val;
> +
> +	mutex_lock(&indio_dev->mlock);
> +
> +	/* prevent BL30 from using the SAR ADC while we are using it */
> +	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
> +			   SAR_ADC_DELAY_KERNEL_BUSY,
> +			   SAR_ADC_DELAY_KERNEL_BUSY);
> +
> +	/* wait until BL30 releases it's lock (so we can use the SAR ADC) */
> +	do {
> +		udelay(1);
> +		regmap_read(priv->regmap, SAR_ADC_DELAY, &val);
> +	} while (val & SAR_ADC_DELAY_BL30_BUSY);
> +}
> +
> +static void meson_saradc_unlock(struct iio_dev *indio_dev)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +
> +	/* allow BL30 to use the SAR ADC again */
> +	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
> +			   SAR_ADC_DELAY_KERNEL_BUSY, 0);
> +
> +	mutex_unlock(&indio_dev->mlock);
> +}
> +
> +static int meson_saradc_get_sample(struct iio_dev *indio_dev,
> +				   const struct iio_chan_spec *chan,
> +				   enum meson_saradc_avg_mode avg_mode,
> +				   enum meson_saradc_num_samples avg_samples,
> +				   int *val)
> +{
> +	int ret, tmp;
> +
> +	meson_saradc_lock(indio_dev);
> +
> +	/* clear old values from the FIFO buffer, ignoring errors */
> +	meson_saradc_read_raw_sample(indio_dev, chan, &tmp);
> +
> +	meson_saradc_set_averaging(indio_dev, chan, avg_mode, avg_samples);
> +
> +	meson_saradc_enable_channel(indio_dev, chan);
> +
> +	meson_saradc_start_sample_engine(indio_dev);
> +	ret = meson_saradc_read_raw_sample(indio_dev, chan, val);
> +	meson_saradc_stop_sample_engine(indio_dev);
> +
> +	meson_saradc_unlock(indio_dev);
> +
> +	if (ret) {
> +		dev_warn(&indio_dev->dev,
> +			 "failed to read sample for channel %d: %d\n",
> +			 chan->channel, ret);
> +		return ret;
> +	}
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static int meson_saradc_iio_info_read_raw(struct iio_dev *indio_dev,
> +					  const struct iio_chan_spec *chan,
> +					  int *val, int *val2, long mask)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		return meson_saradc_get_sample(indio_dev, chan, NO_AVERAGING,
> +					       ONE_SAMPLE, val);
> +		break;
> +
> +	case IIO_CHAN_INFO_AVERAGE_RAW:
> +		return meson_saradc_get_sample(indio_dev, chan, MEAN_AVERAGING,
> +					       EIGHT_SAMPLES, val);
> +		break;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		ret = regulator_get_voltage(priv->vref);
> +		if (ret < 0) {
> +			dev_err(&indio_dev->dev,
> +				"failed to get vref voltage: %d\n", ret);
> +			return ret;
> +		}
> +
> +		*val = ret / 1000;
> +		*val2 = priv->resolution;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int meson_saradc_clk_init(struct iio_dev *indio_dev, void __iomem *base)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	struct clk_init_data init;
> +	char clk_name[32];
> +	const char *clk_parents[1];
> +
> +	snprintf(clk_name, sizeof(clk_name), "%s#adc_div",
> +		 of_node_full_name(indio_dev->dev.of_node));
> +	init.name = devm_kstrdup(&indio_dev->dev, clk_name, GFP_KERNEL);
> +	init.flags = 0;
> +	init.ops = &clk_divider_ops;
> +	clk_parents[0] = __clk_get_name(priv->clkin);
> +	init.parent_names = clk_parents;
> +	init.num_parents = 1;
> +
> +	priv->clk_div.reg = base + SAR_ADC_REG3;
> +	priv->clk_div.shift = SAR_ADC_REG3_ADC_CLK_DIV_SHIFT;
> +	priv->clk_div.width = SAR_ADC_REG3_ADC_CLK_DIV_WIDTH;
> +	priv->clk_div.hw.init = &init;
> +	priv->clk_div.flags = 0;
> +
> +	priv->adc_div_clk = devm_clk_register(&indio_dev->dev,
> +					      &priv->clk_div.hw);
> +	if (WARN_ON(IS_ERR(priv->adc_div_clk)))
> +		return PTR_ERR(priv->adc_div_clk);
> +
> +	snprintf(clk_name, sizeof(clk_name), "%s#adc_en",
> +		 of_node_full_name(indio_dev->dev.of_node));
> +	init.name = devm_kstrdup(&indio_dev->dev, clk_name, GFP_KERNEL);
> +	init.flags = CLK_SET_RATE_PARENT;
> +	init.ops = &clk_gate_ops;
> +	clk_parents[0] = __clk_get_name(priv->adc_div_clk);
> +	init.parent_names = clk_parents;
> +	init.num_parents = 1;
> +
> +	priv->clk_gate.reg = base + SAR_ADC_REG3;
> +	priv->clk_gate.bit_idx = fls(SAR_ADC_REG3_CLK_EN);
> +	priv->clk_gate.hw.init = &init;
> +
> +	priv->adc_clk = devm_clk_register(&indio_dev->dev, &priv->clk_gate.hw);
> +	if (WARN_ON(IS_ERR(priv->adc_clk)))
> +		return PTR_ERR(priv->adc_clk);
> +
> +	return 0;
> +}
> +
> +static int meson_saradc_init(struct iio_dev *indio_dev)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	int regval, ret;
> +
> +	/* make sure we start at CH7 input */
why?  Seems like a little more detail would be good here ;)
> +	meson_saradc_set_channel7_mux(indio_dev, CHAN7_MUX_CH7_INPUT);
> +
> +	regmap_read(priv->regmap, SAR_ADC_REG3, &regval);
> +	if (regval & SAR_ADC_REG3_BL30_INITIALIZED) {
> +		dev_info(&indio_dev->dev, "already initialized by BL30\n");
> +		return 0;
> +	}
> +
> +	dev_info(&indio_dev->dev, "initializing SAR ADC\n");
I'd argue this provides no useful info so should be dropped.
Useful for debugging no doubt, but just noise going forward.
> +
> +	meson_saradc_stop_sample_engine(indio_dev);
> +
> +	/* update the channel 6 MUX to select the temperature sensor */
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
> +			SAR_ADC_REG0_ADC_TEMP_SEN_SEL,
> +			SAR_ADC_REG0_ADC_TEMP_SEN_SEL);
> +
> +	/* disable all channels by default */
> +	regmap_write(priv->regmap, SAR_ADC_CHAN_LIST, 0x0);
> +
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG3,
> +			   SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE, 0);
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG3,
> +			   SAR_ADC_REG3_CNTL_USE_SC_DLY,
> +			   SAR_ADC_REG3_CNTL_USE_SC_DLY);
> +
> +	/* delay between two samples = (10+1) * 1uS */
> +	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
> +			   SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
> +			   FIELD_PREP(SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK, 10));
> +	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
> +			   SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK,
> +			   FIELD_PREP(SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK, 0));
> +
> +	/* delay between two samples = (10+1) * 1uS */
> +	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
> +			   SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
> +			   FIELD_PREP(SAR_ADC_DELAY_INPUT_DLY_CNT_MASK, 10));
> +	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
> +			   SAR_ADC_DELAY_INPUT_DLY_SEL_MASK,
> +			   FIELD_PREP(SAR_ADC_DELAY_INPUT_DLY_SEL_MASK, 1));
> +
Cool. I hadn't come across FIELD_PREP before. Neater and tidier than having
a shift and a mask for at least some usecases.

> +	ret = clk_set_parent(priv->adc_sel_clk, priv->clkin);
> +	if (ret) {
> +		dev_err(&indio_dev->dev,
> +			"failed to set adc parent to clkin\n");
> +		return ret;
> +	}
> +
> +	ret = clk_set_rate(priv->adc_clk, 1200000);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "failed to set adc clock rate\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int meson_saradc_hw_enable(struct iio_dev *indio_dev)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +	int ret;
> +
> +	meson_saradc_lock(indio_dev);
> +
> +	ret = regulator_enable(priv->vref);
> +	if (ret < 0) {
> +		dev_err(&indio_dev->dev, "failed to enable vref regulator\n");
> +		goto err_vref;
> +	}
> +
> +	ret = clk_prepare_enable(priv->core_clk);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "failed to enable core clk\n");
> +		goto err_core_clk;
> +	}
> +
> +	ret = clk_prepare_enable(priv->sana_clk);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "failed to enable sana clk\n");
> +		goto err_sana_clk;
> +	}
> +
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG11,
> +			   SAR_ADC_REG11_BANDGAP_EN, SAR_ADC_REG11_BANDGAP_EN);
Is this controlling an offset for a bandgap or some actual electronics?
Not sure if it should be disabled on error and the datasheets I've found are
far from great!  You disable it in the disable, so I'd expect it to be
unwound on error in here too.
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG3, SAR_ADC_REG3_ADC_EN,
> +			   SAR_ADC_REG3_ADC_EN);
The fact you turn this of in the disable suggests to me that on error
you should be doing it in here too.
> +
> +	udelay(5);
> +
> +	ret = clk_prepare_enable(priv->adc_clk);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "failed to enable adc_en clk\n");
> +		goto err_adc_clk;
> +	}
> +
> +	meson_saradc_unlock(indio_dev);
> +
> +	return 0;
> +
> +err_adc_clk:
> +	clk_disable_unprepare(priv->sana_clk);
> +err_sana_clk:
> +	clk_disable_unprepare(priv->core_clk);
> +err_core_clk:
> +	regulator_disable(priv->vref);
> +err_vref:
> +	meson_saradc_unlock(indio_dev);
> +	return ret;
> +}
> +
> +static void meson_saradc_hw_disable(struct iio_dev *indio_dev)
> +{
> +	struct meson_saradc_priv *priv = iio_priv(indio_dev);
> +
> +	meson_saradc_lock(indio_dev);
> +
> +	clk_disable_unprepare(priv->adc_clk);
> +
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG3, SAR_ADC_REG3_ADC_EN, 0);
> +	regmap_update_bits(priv->regmap, SAR_ADC_REG11,
> +			   SAR_ADC_REG11_BANDGAP_EN, 0);
> +
> +	clk_disable_unprepare(priv->sana_clk);
> +	clk_disable_unprepare(priv->core_clk);
> +
> +	regulator_disable(priv->vref);
> +
> +	meson_saradc_unlock(indio_dev);
> +}
> +
> +static const struct iio_info meson_saradc_iio_info = {
> +	.read_raw = meson_saradc_iio_info_read_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static const struct of_device_id meson_saradc_of_match[] = {
> +	{
> +		.compatible = "amlogic,meson-gxbb-saradc",
> +		.data = (void *)10,
Might have been worth having a structure array indexed from an enum.
For now it is overkill, but seems likely there are a few other differences
that aren't supported yet?
> +	}, {
> +		.compatible = "amlogic,meson-gxl-saradc",
> +		.data = (void *)12,
> +	},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, meson_saradc_of_match);
> +
> +static int meson_saradc_probe(struct platform_device *pdev)
> +{
> +	struct meson_saradc_priv *priv;
> +	struct iio_dev *indio_dev;
> +	struct resource *res;
> +	void __iomem *base;
> +	const struct of_device_id *match;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
> +	if (!indio_dev) {
> +		dev_err(&pdev->dev, "failed allocating iio device\n");
> +		return -ENOMEM;
> +	}
> +
> +	priv = iio_priv(indio_dev);
> +
> +	match = of_match_device(meson_saradc_of_match, &pdev->dev);
> +	priv->resolution = (unsigned long)match->data;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	priv->regmap = devm_regmap_init_mmio(&pdev->dev, base,
> +					     &meson_saradc_regmap_config);
> +	if (IS_ERR(priv->regmap))
> +		return PTR_ERR(priv->regmap);
> +
> +	init_completion(&priv->completion);
> +
> +	priv->clkin = devm_clk_get(&pdev->dev, "clkin");
> +	if (IS_ERR(priv->clkin)) {
> +		dev_err(&pdev->dev, "failed to get clkin\n");
> +		return PTR_ERR(priv->clkin);
> +	}
> +
> +	priv->core_clk = devm_clk_get(&pdev->dev, "core");
> +	if (IS_ERR(priv->core_clk)) {
> +		dev_err(&pdev->dev, "failed to get core clk\n");
> +		return PTR_ERR(priv->core_clk);
> +	}
> +
> +	priv->sana_clk = devm_clk_get(&pdev->dev, "sana");
Oh for a devm_clk_get_optional to handle this boiler plate neatly.
It's been suggested before, but nothing seems to have come of it.

Some array clk get functions might also clean this up a touch.

> +	if (IS_ERR(priv->sana_clk)) {
> +		if (PTR_ERR(priv->sana_clk) == -ENOENT) {
> +			priv->sana_clk = NULL;
> +		} else {
> +			dev_err(&pdev->dev, "failed to get sana clk\n");
> +			return PTR_ERR(priv->sana_clk);
> +		}
> +	}
> +
> +	priv->adc_clk = devm_clk_get(&pdev->dev, "adc_clk");
> +	if (IS_ERR(priv->adc_clk)) {
> +		if (PTR_ERR(priv->adc_clk) == -ENOENT) {
> +			priv->adc_clk = NULL;
> +		} else {
> +			dev_err(&pdev->dev, "failed to get adc clk\n");
> +			return PTR_ERR(priv->adc_clk);
> +		}
> +	}
> +
> +	priv->adc_sel_clk = devm_clk_get(&pdev->dev, "adc_sel");
> +	if (IS_ERR(priv->adc_sel_clk)) {
> +		if (PTR_ERR(priv->adc_sel_clk) == -ENOENT) {
> +			priv->adc_sel_clk = NULL;
> +		} else {
> +			dev_err(&pdev->dev, "failed to get adc_sel clk\n");
> +			return PTR_ERR(priv->adc_sel_clk);
> +		}
> +	}
> +
> +	/* on pre-GXBB SoCs the SAR ADC itself provides the ADC clock: */
> +	if (!priv->adc_clk) {
> +		ret = meson_saradc_clk_init(indio_dev, base);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	priv->vref = devm_regulator_get(&pdev->dev, "vref");
> +	if (IS_ERR(priv->vref)) {
> +		dev_err(&pdev->dev, "failed to get vref regulator\n");
> +		return PTR_ERR(priv->vref);
> +	}
> +
> +	ret = meson_saradc_init(indio_dev);
> +	if (ret)
> +		goto err;
> +
> +	ret = meson_saradc_hw_enable(indio_dev);
> +	if (ret)
> +		goto err;
> +
> +	platform_set_drvdata(pdev, indio_dev);
> +
> +	indio_dev->name = dev_name(&pdev->dev);
> +	indio_dev->dev.parent = &pdev->dev;
> +	indio_dev->dev.of_node = pdev->dev.of_node;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &meson_saradc_iio_info;
> +
> +	indio_dev->channels = meson_saradc_iio_channels;
> +	indio_dev->num_channels = SAR_ADC_NUM_CHANNELS;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret)
> +		goto err_hw;
> +
> +	return 0;
> +
> +err_hw:
> +	meson_saradc_hw_disable(indio_dev);
> +err:
> +	return ret;
> +}
> +
> +static int meson_saradc_remove(struct platform_device *pdev)
> +{
> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> +
> +	meson_saradc_hw_disable(indio_dev);
> +	iio_device_unregister(indio_dev);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int meson_saradc_suspend(struct device *dev)
> +{
> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
> +
> +	meson_saradc_hw_disable(indio_dev);
> +
> +	return 0;
> +}
> +
> +static int meson_saradc_resume(struct device *dev)
> +{
> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
> +
> +	return meson_saradc_hw_enable(indio_dev);
> +}
> +#endif /* CONFIG_PM_SLEEP */
> +
> +static SIMPLE_DEV_PM_OPS(meson_saradc_pm_ops,
> +			 meson_saradc_suspend, meson_saradc_resume);
> +
> +static struct platform_driver meson_saradc_driver = {
> +	.probe		= meson_saradc_probe,
> +	.remove		= meson_saradc_remove,
> +	.driver		= {
> +		.name	= "meson-saradc",
> +		.of_match_table = meson_saradc_of_match,
> +		.pm = &meson_saradc_pm_ops,
> +	},
> +};
> +
> +module_platform_driver(meson_saradc_driver);
> +
> +MODULE_AUTHOR("Martin Blumenstingl <[e-mail]>");
> +MODULE_DESCRIPTION("Amlogic Meson SAR ADC driver");
> +MODULE_LICENSE("GPL v2");
>

Martin Blumenstingl Jan. 14, 2017, 5:44 p.m. UTC | #2

Hi Jonathan,

thank you for the review!
(further comments from me inline)
I think I'll send an updated version on Monday.

On Sat, Jan 14, 2017 at 3:46 PM, Jonathan Cameron <[e-mail]> wrote:
> On 11/01/17 17:43, Martin Blumenstingl wrote:
>> This adds support for the SAR (Successive Approximation Register) ADC
>> on the Amlogic Meson SoCs.
>>
>> The code is based on the public S805 (Meson8b) and S905 (GXBB)
>> datasheets, as well as by reading (various versions of) the vendor
>> driver and by inspecting the registers on the vendor kernels of my
>> testing-hardware.
>>
>> Currently the GXBB, GXL and GXM SoCs are supported. GXBB hardware has
>> 10-bit ADC resolution, while GXL and GXM have 12-bit ADC resolution.
>> The code was written to support older SoCs (Meson8 and Meson8b) as well,
>> but due to lack of actual testing-hardware no of_device_id was added for
>> these.
>>
>> Two "features" from the vendor driver are currently missing:
>> - the vendor driver uses channel #7 for calibration (this improves the
>>   accuracy of the results - in my tests the results were less than 3%
>>   off without calibration compared to the vendor driver). Adding support
>>   for this should be easy, but is not required for most applications.
>> - channel #6 is connected to the SoCs internal temperature sensor.
>>   Adding support for this is probably not so easy since (based on the
>>   u-boot sources) most SoC versions are using different registers and
>>   algorithms for the conversion from "ADC value" to temperature.
>>
>> Supported by the hardware but currently not supported by the driver:
>> - reading multiple channels at the same time (the hardware has a FIFO
>>   buffer which stores multiple results)
>> - continuous sampling (this would require a way to enable this
>>   individually because otherwise the ADC would be drawing power
>>   constantly)
>> - interrupt support (similar to the vendor driver this new driver is
>>   polling the results. It is unclear if the IRQ-mode is supported on
>>   older (Meson6 or Meson8) hardware as well or if there are any errata)
>>
> Russell Cc'd for a quick question on the clk api.
a quick side-note the clk API: my driver is a clock consumer and
provider at the same time. This seems to be a recurring pattern in
Amlogic hardware designs (as the MMC and DWMAC glue drivers are doing
this also), see [0]

> Ideally include a source for datasheets if available. Saves time googling and
> perhaps getting the wrong thing!
OK, will do this in v2

> A few other minor comments inline. Pretty good V1.
thanks :-)

> Jonathan
>> Signed-off-by: Martin Blumenstingl <[e-mail]>
>> ---
>>  drivers/iio/adc/Kconfig        |  12 +
>>  drivers/iio/adc/Makefile       |   1 +
>>  drivers/iio/adc/meson_saradc.c | 860 +++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 873 insertions(+)
>>  create mode 100644 drivers/iio/adc/meson_saradc.c
>>
>> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
>> index 9c8b558ba19e..86059b9b91bf 100644
>> --- a/drivers/iio/adc/Kconfig
>> +++ b/drivers/iio/adc/Kconfig
>> @@ -371,6 +371,18 @@ config MEN_Z188_ADC
>>         This driver can also be built as a module. If so, the module will be
>>         called men_z188_adc.
>>
>> +config MESON_SARADC
>> +     tristate "Amlogic Meson SAR ADC driver"
>> +     default ARCH_MESON
>> +     depends on OF && COMMON_CLK && (ARCH_MESON || COMPILE_TEST)
>> +     select REGMAP_MMIO
>> +     help
>> +       Say yes here to build support for the SAR ADC found in Amlogic Meson
>> +       SoCs.
>> +
>> +       To compile this driver as a module, choose M here: the
>> +       module will be called meson_saradc.
>> +
>>  config MXS_LRADC
>>          tristate "Freescale i.MX23/i.MX28 LRADC"
>>          depends on (ARCH_MXS || COMPILE_TEST) && HAS_IOMEM
>> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
>> index d36c4be8d1fc..de05b9e75f8f 100644
>> --- a/drivers/iio/adc/Makefile
>> +++ b/drivers/iio/adc/Makefile
>> @@ -36,6 +36,7 @@ obj-$(CONFIG_MCP320X) += mcp320x.o
>>  obj-$(CONFIG_MCP3422) += mcp3422.o
>>  obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
>>  obj-$(CONFIG_MEN_Z188_ADC) += men_z188_adc.o
>> +obj-$(CONFIG_MESON_SARADC) += meson_saradc.o
>>  obj-$(CONFIG_MXS_LRADC) += mxs-lradc.o
>>  obj-$(CONFIG_NAU7802) += nau7802.o
>>  obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
>> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
>> new file mode 100644
>> index 000000000000..06e8ac620385
>> --- /dev/null
>> +++ b/drivers/iio/adc/meson_saradc.c
>> @@ -0,0 +1,860 @@
>> +/*
>> + * Amlogic Meson Successive Approximation Register (SAR) A/D Converter
>> + *
>> + * Copyright (C) 2017 Martin Blumenstingl <[e-mail]>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/bitfield.h>
>> +#include <linux/clk-provider.h>
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/io.h>
>> +#include <linux/iio/iio.h>
>> +#include <linux/of.h>
>> +#include <linux/of_device.h>
>> +#include <linux/clk.h>
>> +#include <linux/completion.h>
>> +#include <linux/delay.h>
>> +#include <linux/reset.h>
>> +#include <linux/regmap.h>
>> +#include <linux/regulator/consumer.h>
>> +
>> +#define SAR_ADC_REG0                                         0x00
>> +     #define SAR_ADC_REG0_PANEL_DETECT                       BIT(31)
>> +     #define SAR_ADC_REG0_BUSY_MASK                          GENMASK(30, 28)
>> +     #define SAR_ADC_REG0_DELTA_BUSY                         BIT(30)
>> +     #define SAR_ADC_REG0_AVG_BUSY                           BIT(29)
>> +     #define SAR_ADC_REG0_SAMPLE_BUSY                        BIT(28)
>> +     #define SAR_ADC_REG0_FIFO_FULL                          BIT(27)
>> +     #define SAR_ADC_REG0_FIFO_EMPTY                         BIT(26)
>> +     #define SAR_ADC_REG0_FIFO_COUNT_MASK                    GENMASK(25, 21)
>> +     #define SAR_ADC_REG0_ADC_BIAS_CTRL_MASK                 GENMASK(20, 19)
>> +     #define SAR_ADC_REG0_CURR_CHAN_ID_MASK                  GENMASK(18, 16)
>> +     #define SAR_ADC_REG0_ADC_TEMP_SEN_SEL                   BIT(15)
>> +     #define SAR_ADC_REG0_SAMPLING_STOP                      BIT(14)
>> +     #define SAR_ADC_REG0_CHAN_DELTA_EN_MASK                 GENMASK(13, 12)
>> +     #define SAR_ADC_REG0_DETECT_IRQ_POL                     BIT(10)
>> +     #define SAR_ADC_REG0_DETECT_IRQ_EN                      BIT(9)
>> +     #define SAR_ADC_REG0_FIFO_CNT_IRQ_MASK                  GENMASK(8, 4)
>> +     #define SAR_ADC_REG0_FIFO_IRQ_EN                        BIT(3)
>> +     #define SAR_ADC_REG0_SAMPLING_START                     BIT(2)
>> +     #define SAR_ADC_REG0_CONTINUOUS_EN                      BIT(1)
>> +     #define SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE               BIT(0)
>> +
>> +#define SAR_ADC_CHAN_LIST                                    0x04
>> +     #define SAR_ADC_CHAN_LIST_MAX_INDEX_MASK                GENMASK(26, 24)
>> +     #define SAR_ADC_CHAN_CHAN_ENTRY_MASK(_chan)             \
>> +                                     (GENMASK(2, 0) << (_chan * 3))
>> +
>> +#define SAR_ADC_AVG_CNTL                                     0x08
>> +     #define SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(_chan)          \
>> +                                     (16 + (_chan * 2))
>> +     #define SAR_ADC_AVG_CNTL_AVG_MODE_MASK(_chan)           \
>> +                                     (GENMASK(17, 16) << (_chan * 2))
>> +     #define SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(_chan)       \
>> +                                     (0 + (_chan * 2))
>> +     #define SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(_chan)        \
>> +                                     (GENMASK(1, 0) << (_chan * 2))
>> +
>> +#define SAR_ADC_REG3                                         0x0c
>> +     #define SAR_ADC_REG3_CNTL_USE_SC_DLY                    BIT(31)
>> +     #define SAR_ADC_REG3_CLK_EN                             BIT(30)
>> +     #define SAR_ADC_REG3_BL30_INITIALIZED                   BIT(28)
>> +     #define SAR_ADC_REG3_CTRL_CONT_RING_COUNTER_EN          BIT(27)
>> +     #define SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE          BIT(26)
>> +     #define SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK            GENMASK(25, 23)
>> +     #define SAR_ADC_REG3_DETECT_EN                          BIT(22)
>> +     #define SAR_ADC_REG3_ADC_EN                             BIT(21)
>> +     #define SAR_ADC_REG3_PANEL_DETECT_COUNT_MASK            GENMASK(20, 18)
>> +     #define SAR_ADC_REG3_PANEL_DETECT_FILTER_TB_MASK        GENMASK(17, 16)
>> +     #define SAR_ADC_REG3_ADC_CLK_DIV_SHIFT                  10
>> +     #define SAR_ADC_REG3_ADC_CLK_DIV_WIDTH                  5
>> +     #define SAR_ADC_REG3_ADC_CLK_DIV_MASK                   GENMASK(15, 10)
>> +     #define SAR_ADC_REG3_BLOCK_DLY_SEL_MASK                 GENMASK(9, 8)
>> +     #define SAR_ADC_REG3_BLOCK_DLY_MASK                     GENMASK(7, 0)
>> +
>> +#define SAR_ADC_DELAY                                                0x10
>> +     #define SAR_ADC_DELAY_INPUT_DLY_SEL_MASK                GENMASK(25, 24)
>> +     #define SAR_ADC_DELAY_BL30_BUSY                         BIT(15)
>> +     #define SAR_ADC_DELAY_KERNEL_BUSY                       BIT(14)
>> +     #define SAR_ADC_DELAY_INPUT_DLY_CNT_MASK                GENMASK(23, 16)
>> +     #define SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK               GENMASK(9, 8)
>> +     #define SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK               GENMASK(7, 0)
>> +
>> +#define SAR_ADC_LAST_RD                                              0x14
>> +     #define SAR_ADC_LAST_RD_LAST_CHANNEL1_MASK              GENMASK(23, 16)
>> +     #define SAR_ADC_LAST_RD_LAST_CHANNEL0_MASK              GENMASK(9, 0)
>> +
>> +#define SAR_ADC_FIFO_RD                                              0x18
>> +     #define SAR_ADC_FIFO_RD_CHAN_ID_MASK                    GENMASK(14, 12)
>> +     #define SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK               GENMASK(11, 0)
>> +
>> +#define SAR_ADC_AUX_SW                                               0x1c
>> +     #define SAR_ADC_AUX_SW_MUX_SEL_CHAN_MASK(_chan)         \
>> +                                     (GENMASK(10, 8) << ((_chan - 2) * 2))
>> +     #define SAR_ADC_AUX_SW_VREF_P_MUX                       BIT(6)
>> +     #define SAR_ADC_AUX_SW_VREF_N_MUX                       BIT(5)
>> +     #define SAR_ADC_AUX_SW_MODE_SEL                         BIT(4)
>> +     #define SAR_ADC_AUX_SW_YP_DRIVE_SW                      BIT(3)
>> +     #define SAR_ADC_AUX_SW_XP_DRIVE_SW                      BIT(2)
>> +     #define SAR_ADC_AUX_SW_YM_DRIVE_SW                      BIT(1)
>> +     #define SAR_ADC_AUX_SW_XM_DRIVE_SW                      BIT(0)
>> +
>> +#define SAR_ADC_CHAN_10_SW                                   0x20
>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_MUX_SEL_MASK           GENMASK(25, 23)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_VREF_P_MUX             BIT(22)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_VREF_N_MUX             BIT(21)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_MODE_SEL               BIT(20)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_YP_DRIVE_SW            BIT(19)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_XP_DRIVE_SW            BIT(18)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_YM_DRIVE_SW            BIT(17)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_XM_DRIVE_SW            BIT(16)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_MUX_SEL_MASK           GENMASK(9, 7)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_VREF_P_MUX             BIT(6)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_VREF_N_MUX             BIT(5)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_MODE_SEL               BIT(4)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_YP_DRIVE_SW            BIT(3)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_XP_DRIVE_SW            BIT(2)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_YM_DRIVE_SW            BIT(1)
>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_XM_DRIVE_SW            BIT(0)
>> +
>> +#define SAR_ADC_DETECT_IDLE_SW                                       0x24
>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_SW_EN             BIT(26)
>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK     GENMASK(25, 23)
>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_VREF_P_MUX   BIT(22)
>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_VREF_N_MUX   BIT(21)
>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_SEL          BIT(20)
>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_YP_DRIVE_SW  BIT(19)
>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_XP_DRIVE_SW  BIT(18)
>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_YM_DRIVE_SW  BIT(17)
>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_XM_DRIVE_SW  BIT(16)
>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK   GENMASK(9, 7)
>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_VREF_P_MUX     BIT(6)
>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_VREF_N_MUX     BIT(5)
>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_SEL            BIT(4)
>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_YP_DRIVE_SW    BIT(3)
>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_XP_DRIVE_SW    BIT(2)
>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_YM_DRIVE_SW    BIT(1)
>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_XM_DRIVE_SW    BIT(0)
>> +
>> +#define SAR_ADC_DELTA_10                                     0x28
>> +     #define SAR_ADC_DELTA_10_TEMP_SEL                       BIT(27)
>> +     #define SAR_ADC_DELTA_10_TS_REVE1                       BIT(26)
>> +     #define SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_SHIFT        16
>> +     #define SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_MASK         GENMASK(25, 16)
>> +     #define SAR_ADC_DELTA_10_TS_REVE0                       BIT(15)
>> +     #define SAR_ADC_DELTA_10_TS_C_SHIFT                     11
>> +     #define SAR_ADC_DELTA_10_TS_C_MASK                      GENMASK(14, 11)
>> +     #define SAR_ADC_DELTA_10_TS_VBG_EN                      BIT(10)
>> +     #define SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_SHIFT        0
>> +     #define SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_MASK         GENMASK(9, 0)
>> +
>> +/* NOTE: registers from here are undocumented (the vendor Linux kernel driver
>> + * and u-boot source served as reference). These only seem to be relevant on
>> + * GXBB and newer.
>> + */
>> +#define SAR_ADC_REG11                                                0x2c
>> +     #define SAR_ADC_REG11_BANDGAP_EN                        BIT(13)
>> +
>> +#define SAR_ADC_REG13                                                0x34
>> +     #define SAR_ADC_REG13_12BIT_CALIBRATION_MASK            GENMASK(13, 8)
>> +
>> +#define SAR_ADC_MAX_FIFO_SIZE                32
>> +#define SAR_ADC_NUM_CHANNELS         ARRAY_SIZE(meson_saradc_iio_channels)
>> +#define SAR_ADC_VALUE_MASK(_priv)    (BIT(_priv->resolution) - 1)
>> +
>> +#define MESON_SAR_ADC_CHAN(_chan, _type) {                           \
>> +     .type = _type,                                                  \
>> +     .indexed = true,                                                \
>> +     .channel = _chan,                                               \
>> +     .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |                  \
>> +                             BIT(IIO_CHAN_INFO_AVERAGE_RAW),         \
>> +     .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),           \
>> +     .datasheet_name = "SAR_ADC_CH"#_chan,                           \
>> +}
>> +
>> +/* TODO: the hardware supports IIO_TEMP for channel 6 as well which is
> Multline comment syntax.
I got this wrong in 2 other places as well. will be fixed in v2, thanks!

>> + * currently not supported by this driver.
>> + */
>> +static const struct iio_chan_spec meson_saradc_iio_channels[] = {
>> +     MESON_SAR_ADC_CHAN(0, IIO_VOLTAGE),
>> +     MESON_SAR_ADC_CHAN(1, IIO_VOLTAGE),
>> +     MESON_SAR_ADC_CHAN(2, IIO_VOLTAGE),
>> +     MESON_SAR_ADC_CHAN(3, IIO_VOLTAGE),
>> +     MESON_SAR_ADC_CHAN(4, IIO_VOLTAGE),
>> +     MESON_SAR_ADC_CHAN(5, IIO_VOLTAGE),
>> +     MESON_SAR_ADC_CHAN(6, IIO_VOLTAGE),
>> +     MESON_SAR_ADC_CHAN(7, IIO_VOLTAGE),
>> +     IIO_CHAN_SOFT_TIMESTAMP(8),
>> +};
>> +
>> +enum meson_saradc_avg_mode {
>> +     NO_AVERAGING = 0x0,
>> +     MEAN_AVERAGING = 0x1,
>> +     MEDIAN_AVERAGING = 0x2,
>> +};
>> +
>> +enum meson_saradc_num_samples {
>> +     ONE_SAMPLE = 0x0,
>> +     TWO_SAMPLES = 0x1,
>> +     FOUR_SAMPLES = 0x2,
>> +     EIGHT_SAMPLES = 0x3,
>> +};
>> +
>> +enum meson_saradc_chan7_mux_sel {
>> +     CHAN7_MUX_VSS = 0x0,
>> +     CHAN7_MUX_VDD_DIV4 = 0x1,
>> +     CHAN7_MUX_VDD_DIV2 = 0x2,
>> +     CHAN7_MUX_VDD_MUL3_DIV4 = 0x3,
>> +     CHAN7_MUX_VDD = 0x4,
>> +     CHAN7_MUX_CH7_INPUT = 0x7,
>> +};
>> +
>> +struct meson_saradc_priv {
>> +     struct regmap                   *regmap;
>> +     struct clk                      *clkin;
>> +     struct clk                      *core_clk;
>> +     struct clk                      *sana_clk;
>> +     struct clk                      *adc_sel_clk;
>> +     struct clk                      *adc_clk;
>> +     struct clk_gate                 clk_gate;
>> +     struct clk                      *adc_div_clk;
>> +     struct clk_divider              clk_div;
>> +     struct regulator                *vref;
>> +     struct completion               completion;
>> +     u8                              resolution;
>> +};
>> +
>> +static const struct regmap_config meson_saradc_regmap_config = {
>> +     .reg_bits = 8,
>> +     .val_bits = 32,
>> +     .reg_stride = 4,
>> +     .max_register = SAR_ADC_REG13,
>> +};
>> +
>> +static unsigned int meson_saradc_get_fifo_count(struct iio_dev *indio_dev)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     u32 regval;
>> +
>> +     regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
>> +
>> +     return FIELD_GET(SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
>> +}
>> +
>> +static int meson_saradc_wait_busy_clear(struct iio_dev *indio_dev)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     int regval, timeout = 10000;
>> +
>> +     do {
>> +             udelay(1);
>> +             regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
>> +     } while (FIELD_GET(SAR_ADC_REG0_BUSY_MASK, regval) && timeout--);
>> +
>> +     if (timeout < 0)
>> +             return -ETIMEDOUT;
>> +
>> +     return 0;
>> +}
>> +
>> +static int meson_saradc_read_raw_sample(struct iio_dev *indio_dev,
>> +                                     const struct iio_chan_spec *chan,
>> +                                     int *val)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     int ret, regval, fifo_chan, fifo_val, sum = 0, count = 0;
>> +
>> +     ret = meson_saradc_wait_busy_clear(indio_dev);
>> +     if (ret)
>> +             return ret;
>> +
>> +     regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
>> +
>> +     while (meson_saradc_get_fifo_count(indio_dev) > 0 &&
>> +            count < SAR_ADC_MAX_FIFO_SIZE) {
>> +             regmap_read(priv->regmap, SAR_ADC_FIFO_RD, &regval);
>> +
>> +             fifo_chan = FIELD_GET(SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
>> +             if (fifo_chan == chan->channel) {
>> +                     fifo_val = FIELD_GET(SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK,
>> +                                          regval) & SAR_ADC_VALUE_MASK(priv);
>> +                     sum += fifo_val;
>> +                     count++;
>> +             }
>> +     }
>> +
>> +     if (!count)
>> +             return -ENOENT;
>> +
>> +     *val = sum / count;
>> +
>> +     return 0;
>> +}
>> +
>> +static void meson_saradc_set_averaging(struct iio_dev *indio_dev,
>> +                                    const struct iio_chan_spec *chan,
>> +                                    enum meson_saradc_avg_mode mode,
>> +                                    enum meson_saradc_num_samples samples)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     u32 val;
>> +
>> +     val = samples << SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(chan->channel);
>> +     regmap_update_bits(priv->regmap, SAR_ADC_AVG_CNTL,
>> +                        SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(chan->channel),
>> +                        val);
>> +
>> +     val = mode << SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(chan->channel);
>> +     regmap_update_bits(priv->regmap, SAR_ADC_AVG_CNTL,
>> +                        SAR_ADC_AVG_CNTL_AVG_MODE_MASK(chan->channel), val);
>> +}
>> +
>> +static void meson_saradc_enable_channel(struct iio_dev *indio_dev,
>> +                                     const struct iio_chan_spec *chan)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     u32 regval;
>> +
>> +     /* the SAR ADC engine allows sampling multiple channels at the same
>> +      * time. to keep it simple we're only working with one *internal*
>> +      * channel, which starts counting at index 0 (which means: count = 1).
>> +      */
>> +     regval = FIELD_PREP(SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, 0);
>> +     regmap_update_bits(priv->regmap, SAR_ADC_CHAN_LIST,
>> +                        SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, regval);
>> +
>> +     /* map channel index 0 to the channel which we want to read */
>> +     regval = FIELD_PREP(SAR_ADC_CHAN_CHAN_ENTRY_MASK(0), chan->channel);
>> +     regmap_update_bits(priv->regmap, SAR_ADC_CHAN_LIST,
>> +                        SAR_ADC_CHAN_CHAN_ENTRY_MASK(0), regval);
>> +
>> +     regval = FIELD_PREP(SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK,
>> +                         chan->channel);
>> +     regmap_update_bits(priv->regmap, SAR_ADC_DETECT_IDLE_SW,
>> +                        SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK,
>> +                        regval);
>> +
>> +     regval = FIELD_PREP(SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK,
>> +                         chan->channel);
>> +     regmap_update_bits(priv->regmap, SAR_ADC_DETECT_IDLE_SW,
>> +                        SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK,
>> +                        regval);
>> +
>> +     if (chan->channel == 6)
>> +             regmap_update_bits(priv->regmap, SAR_ADC_DELTA_10,
>> +                                SAR_ADC_DELTA_10_TEMP_SEL, 0);
>> +}
>> +
>> +static void meson_saradc_set_channel7_mux(struct iio_dev *indio_dev,
>> +                                       enum meson_saradc_chan7_mux_sel sel)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     u32 regval;
>> +
>> +     regval = FIELD_PREP(SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, sel);
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3,
>> +                        SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, regval);
>> +
>> +     usleep_range(10, 20);
>> +}
>> +
>> +static void meson_saradc_start_sample_engine(struct iio_dev *indio_dev)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>> +                        SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE,
>> +                        SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE);
>> +
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>> +                        SAR_ADC_REG0_SAMPLING_START,
>> +                        SAR_ADC_REG0_SAMPLING_START);
>> +}
>> +
>> +static void meson_saradc_stop_sample_engine(struct iio_dev *indio_dev)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>> +                        SAR_ADC_REG0_SAMPLING_STOP,
>> +                        SAR_ADC_REG0_SAMPLING_STOP);
>> +
>> +     /* wait until all modules are stopped */
>> +     meson_saradc_wait_busy_clear(indio_dev);
>> +
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>> +                        SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE, 0);
>> +}
>> +
>> +static void meson_saradc_lock(struct iio_dev *indio_dev)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     int val;
>> +
>> +     mutex_lock(&indio_dev->mlock);
>> +
>> +     /* prevent BL30 from using the SAR ADC while we are using it */
>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>> +                        SAR_ADC_DELAY_KERNEL_BUSY,
>> +                        SAR_ADC_DELAY_KERNEL_BUSY);
>> +
>> +     /* wait until BL30 releases it's lock (so we can use the SAR ADC) */
>> +     do {
>> +             udelay(1);
>> +             regmap_read(priv->regmap, SAR_ADC_DELAY, &val);
>> +     } while (val & SAR_ADC_DELAY_BL30_BUSY);
>> +}
>> +
>> +static void meson_saradc_unlock(struct iio_dev *indio_dev)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +
>> +     /* allow BL30 to use the SAR ADC again */
>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>> +                        SAR_ADC_DELAY_KERNEL_BUSY, 0);
>> +
>> +     mutex_unlock(&indio_dev->mlock);
>> +}
>> +
>> +static int meson_saradc_get_sample(struct iio_dev *indio_dev,
>> +                                const struct iio_chan_spec *chan,
>> +                                enum meson_saradc_avg_mode avg_mode,
>> +                                enum meson_saradc_num_samples avg_samples,
>> +                                int *val)
>> +{
>> +     int ret, tmp;
>> +
>> +     meson_saradc_lock(indio_dev);
>> +
>> +     /* clear old values from the FIFO buffer, ignoring errors */
>> +     meson_saradc_read_raw_sample(indio_dev, chan, &tmp);
>> +
>> +     meson_saradc_set_averaging(indio_dev, chan, avg_mode, avg_samples);
>> +
>> +     meson_saradc_enable_channel(indio_dev, chan);
>> +
>> +     meson_saradc_start_sample_engine(indio_dev);
>> +     ret = meson_saradc_read_raw_sample(indio_dev, chan, val);
>> +     meson_saradc_stop_sample_engine(indio_dev);
>> +
>> +     meson_saradc_unlock(indio_dev);
>> +
>> +     if (ret) {
>> +             dev_warn(&indio_dev->dev,
>> +                      "failed to read sample for channel %d: %d\n",
>> +                      chan->channel, ret);
>> +             return ret;
>> +     }
>> +
>> +     return IIO_VAL_INT;
>> +}
>> +
>> +static int meson_saradc_iio_info_read_raw(struct iio_dev *indio_dev,
>> +                                       const struct iio_chan_spec *chan,
>> +                                       int *val, int *val2, long mask)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     int ret;
>> +
>> +     switch (mask) {
>> +     case IIO_CHAN_INFO_RAW:
>> +             return meson_saradc_get_sample(indio_dev, chan, NO_AVERAGING,
>> +                                            ONE_SAMPLE, val);
>> +             break;
>> +
>> +     case IIO_CHAN_INFO_AVERAGE_RAW:
>> +             return meson_saradc_get_sample(indio_dev, chan, MEAN_AVERAGING,
>> +                                            EIGHT_SAMPLES, val);
>> +             break;
>> +
>> +     case IIO_CHAN_INFO_SCALE:
>> +             ret = regulator_get_voltage(priv->vref);
>> +             if (ret < 0) {
>> +                     dev_err(&indio_dev->dev,
>> +                             "failed to get vref voltage: %d\n", ret);
>> +                     return ret;
>> +             }
>> +
>> +             *val = ret / 1000;
>> +             *val2 = priv->resolution;
>> +             return IIO_VAL_FRACTIONAL_LOG2;
>> +
>> +     default:
>> +             return -EINVAL;
>> +     }
>> +}
>> +
>> +static int meson_saradc_clk_init(struct iio_dev *indio_dev, void __iomem *base)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     struct clk_init_data init;
>> +     char clk_name[32];
>> +     const char *clk_parents[1];
>> +
>> +     snprintf(clk_name, sizeof(clk_name), "%s#adc_div",
>> +              of_node_full_name(indio_dev->dev.of_node));
>> +     init.name = devm_kstrdup(&indio_dev->dev, clk_name, GFP_KERNEL);
>> +     init.flags = 0;
>> +     init.ops = &clk_divider_ops;
>> +     clk_parents[0] = __clk_get_name(priv->clkin);
>> +     init.parent_names = clk_parents;
>> +     init.num_parents = 1;
>> +
>> +     priv->clk_div.reg = base + SAR_ADC_REG3;
>> +     priv->clk_div.shift = SAR_ADC_REG3_ADC_CLK_DIV_SHIFT;
>> +     priv->clk_div.width = SAR_ADC_REG3_ADC_CLK_DIV_WIDTH;
>> +     priv->clk_div.hw.init = &init;
>> +     priv->clk_div.flags = 0;
>> +
>> +     priv->adc_div_clk = devm_clk_register(&indio_dev->dev,
>> +                                           &priv->clk_div.hw);
>> +     if (WARN_ON(IS_ERR(priv->adc_div_clk)))
>> +             return PTR_ERR(priv->adc_div_clk);
>> +
>> +     snprintf(clk_name, sizeof(clk_name), "%s#adc_en",
>> +              of_node_full_name(indio_dev->dev.of_node));
>> +     init.name = devm_kstrdup(&indio_dev->dev, clk_name, GFP_KERNEL);
>> +     init.flags = CLK_SET_RATE_PARENT;
>> +     init.ops = &clk_gate_ops;
>> +     clk_parents[0] = __clk_get_name(priv->adc_div_clk);
>> +     init.parent_names = clk_parents;
>> +     init.num_parents = 1;
>> +
>> +     priv->clk_gate.reg = base + SAR_ADC_REG3;
>> +     priv->clk_gate.bit_idx = fls(SAR_ADC_REG3_CLK_EN);
>> +     priv->clk_gate.hw.init = &init;
>> +
>> +     priv->adc_clk = devm_clk_register(&indio_dev->dev, &priv->clk_gate.hw);
>> +     if (WARN_ON(IS_ERR(priv->adc_clk)))
>> +             return PTR_ERR(priv->adc_clk);
>> +
>> +     return 0;
>> +}
>> +
>> +static int meson_saradc_init(struct iio_dev *indio_dev)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     int regval, ret;
>> +
>> +     /* make sure we start at CH7 input */
> why?  Seems like a little more detail would be good here ;)
I'll change this to "make sure we start at CH7 input since the other
muxes are only used for internal calibration." in v2

>> +     meson_saradc_set_channel7_mux(indio_dev, CHAN7_MUX_CH7_INPUT);
>> +
>> +     regmap_read(priv->regmap, SAR_ADC_REG3, &regval);
>> +     if (regval & SAR_ADC_REG3_BL30_INITIALIZED) {
>> +             dev_info(&indio_dev->dev, "already initialized by BL30\n");
>> +             return 0;
>> +     }
>> +
>> +     dev_info(&indio_dev->dev, "initializing SAR ADC\n");
> I'd argue this provides no useful info so should be dropped.
> Useful for debugging no doubt, but just noise going forward.
do you want me to remove them or should I turn them into dev_dbg() (so
they can be enabled for debugging purposes)?

>> +
>> +     meson_saradc_stop_sample_engine(indio_dev);
>> +
>> +     /* update the channel 6 MUX to select the temperature sensor */
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>> +                     SAR_ADC_REG0_ADC_TEMP_SEN_SEL,
>> +                     SAR_ADC_REG0_ADC_TEMP_SEN_SEL);
>> +
>> +     /* disable all channels by default */
>> +     regmap_write(priv->regmap, SAR_ADC_CHAN_LIST, 0x0);
>> +
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3,
>> +                        SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE, 0);
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3,
>> +                        SAR_ADC_REG3_CNTL_USE_SC_DLY,
>> +                        SAR_ADC_REG3_CNTL_USE_SC_DLY);
>> +
>> +     /* delay between two samples = (10+1) * 1uS */
>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>> +                        SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
>> +                        FIELD_PREP(SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK, 10));
>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>> +                        SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK,
>> +                        FIELD_PREP(SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK, 0));
>> +
>> +     /* delay between two samples = (10+1) * 1uS */
>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>> +                        SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
>> +                        FIELD_PREP(SAR_ADC_DELAY_INPUT_DLY_CNT_MASK, 10));
>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>> +                        SAR_ADC_DELAY_INPUT_DLY_SEL_MASK,
>> +                        FIELD_PREP(SAR_ADC_DELAY_INPUT_DLY_SEL_MASK, 1));
>> +
> Cool. I hadn't come across FIELD_PREP before. Neater and tidier than having
> a shift and a mask for at least some usecases.
I think these were introduced with v4.9. I like them because I tend
use GENMASK() incorrectly and with those macros I get an error at
compile-time (without having to debug my code at all)

>> +     ret = clk_set_parent(priv->adc_sel_clk, priv->clkin);
>> +     if (ret) {
>> +             dev_err(&indio_dev->dev,
>> +                     "failed to set adc parent to clkin\n");
>> +             return ret;
>> +     }
>> +
>> +     ret = clk_set_rate(priv->adc_clk, 1200000);
>> +     if (ret) {
>> +             dev_err(&indio_dev->dev, "failed to set adc clock rate\n");
>> +             return ret;
>> +     }
>> +
>> +     return 0;
>> +}
>> +
>> +static int meson_saradc_hw_enable(struct iio_dev *indio_dev)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +     int ret;
>> +
>> +     meson_saradc_lock(indio_dev);
>> +
>> +     ret = regulator_enable(priv->vref);
>> +     if (ret < 0) {
>> +             dev_err(&indio_dev->dev, "failed to enable vref regulator\n");
>> +             goto err_vref;
>> +     }
>> +
>> +     ret = clk_prepare_enable(priv->core_clk);
>> +     if (ret) {
>> +             dev_err(&indio_dev->dev, "failed to enable core clk\n");
>> +             goto err_core_clk;
>> +     }
>> +
>> +     ret = clk_prepare_enable(priv->sana_clk);
>> +     if (ret) {
>> +             dev_err(&indio_dev->dev, "failed to enable sana clk\n");
>> +             goto err_sana_clk;
>> +     }
>> +
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG11,
>> +                        SAR_ADC_REG11_BANDGAP_EN, SAR_ADC_REG11_BANDGAP_EN);
> Is this controlling an offset for a bandgap or some actual electronics?
> Not sure if it should be disabled on error and the datasheets I've found are
> far from great!  You disable it in the disable, so I'd expect it to be
> unwound on error in here too.
actually the bandgap is not documented at all :(

>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3, SAR_ADC_REG3_ADC_EN,
>> +                        SAR_ADC_REG3_ADC_EN);
> The fact you turn this of in the disable suggests to me that on error
> you should be doing it in here too.
I will disable this along with SAR_ADC_REG11_BANDGAP_EN in the
err_adc_clk label, thanks for spotting this.

>> +
>> +     udelay(5);
>> +
>> +     ret = clk_prepare_enable(priv->adc_clk);
>> +     if (ret) {
>> +             dev_err(&indio_dev->dev, "failed to enable adc_en clk\n");
>> +             goto err_adc_clk;
>> +     }
>> +
>> +     meson_saradc_unlock(indio_dev);
>> +
>> +     return 0;
>> +
>> +err_adc_clk:
>> +     clk_disable_unprepare(priv->sana_clk);
>> +err_sana_clk:
>> +     clk_disable_unprepare(priv->core_clk);
>> +err_core_clk:
>> +     regulator_disable(priv->vref);
>> +err_vref:
>> +     meson_saradc_unlock(indio_dev);
>> +     return ret;
>> +}
>> +
>> +static void meson_saradc_hw_disable(struct iio_dev *indio_dev)
>> +{
>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>> +
>> +     meson_saradc_lock(indio_dev);
>> +
>> +     clk_disable_unprepare(priv->adc_clk);
>> +
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3, SAR_ADC_REG3_ADC_EN, 0);
>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG11,
>> +                        SAR_ADC_REG11_BANDGAP_EN, 0);
>> +
>> +     clk_disable_unprepare(priv->sana_clk);
>> +     clk_disable_unprepare(priv->core_clk);
>> +
>> +     regulator_disable(priv->vref);
>> +
>> +     meson_saradc_unlock(indio_dev);
>> +}
>> +
>> +static const struct iio_info meson_saradc_iio_info = {
>> +     .read_raw = meson_saradc_iio_info_read_raw,
>> +     .driver_module = THIS_MODULE,
>> +};
>> +
>> +static const struct of_device_id meson_saradc_of_match[] = {
>> +     {
>> +             .compatible = "amlogic,meson-gxbb-saradc",
>> +             .data = (void *)10,
> Might have been worth having a structure array indexed from an enum.
> For now it is overkill, but seems likely there are a few other differences
> that aren't supported yet?
what do you mean with "structure array indexed from an enum"? I can
introduce some match-specific struct if you want (just like it's done
in rockchip_saradc.c with "struct rockchip_saradc_data").

>> +     }, {
>> +             .compatible = "amlogic,meson-gxl-saradc",
>> +             .data = (void *)12,
>> +     },
>> +     {},
>> +};
>> +MODULE_DEVICE_TABLE(of, meson_saradc_of_match);
>> +
>> +static int meson_saradc_probe(struct platform_device *pdev)
>> +{
>> +     struct meson_saradc_priv *priv;
>> +     struct iio_dev *indio_dev;
>> +     struct resource *res;
>> +     void __iomem *base;
>> +     const struct of_device_id *match;
>> +     int ret;
>> +
>> +     indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
>> +     if (!indio_dev) {
>> +             dev_err(&pdev->dev, "failed allocating iio device\n");
>> +             return -ENOMEM;
>> +     }
>> +
>> +     priv = iio_priv(indio_dev);
>> +
>> +     match = of_match_device(meson_saradc_of_match, &pdev->dev);
>> +     priv->resolution = (unsigned long)match->data;
>> +
>> +     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +     base = devm_ioremap_resource(&pdev->dev, res);
>> +     if (IS_ERR(base))
>> +             return PTR_ERR(base);
>> +
>> +     priv->regmap = devm_regmap_init_mmio(&pdev->dev, base,
>> +                                          &meson_saradc_regmap_config);
>> +     if (IS_ERR(priv->regmap))
>> +             return PTR_ERR(priv->regmap);
>> +
>> +     init_completion(&priv->completion);
>> +
>> +     priv->clkin = devm_clk_get(&pdev->dev, "clkin");
>> +     if (IS_ERR(priv->clkin)) {
>> +             dev_err(&pdev->dev, "failed to get clkin\n");
>> +             return PTR_ERR(priv->clkin);
>> +     }
>> +
>> +     priv->core_clk = devm_clk_get(&pdev->dev, "core");
>> +     if (IS_ERR(priv->core_clk)) {
>> +             dev_err(&pdev->dev, "failed to get core clk\n");
>> +             return PTR_ERR(priv->core_clk);
>> +     }
>> +
>> +     priv->sana_clk = devm_clk_get(&pdev->dev, "sana");
> Oh for a devm_clk_get_optional to handle this boiler plate neatly.
> It's been suggested before, but nothing seems to have come of it.
I guess quite a few drivers would benefit from that. maybe we should
take this to the linux-clk list again?

> Some array clk get functions might also clean this up a touch.
yes, unfortunately in this case it's not that easy as it would have to
allow a mix of mandatory and optional clocks. Additionally I cannot
bulk-enable them unconditionally since some of these are simple gates,
others need to be reparented and for some the rate has to be set.

>> +     if (IS_ERR(priv->sana_clk)) {
>> +             if (PTR_ERR(priv->sana_clk) == -ENOENT) {
>> +                     priv->sana_clk = NULL;
>> +             } else {
>> +                     dev_err(&pdev->dev, "failed to get sana clk\n");
>> +                     return PTR_ERR(priv->sana_clk);
>> +             }
>> +     }
>> +
>> +     priv->adc_clk = devm_clk_get(&pdev->dev, "adc_clk");
>> +     if (IS_ERR(priv->adc_clk)) {
>> +             if (PTR_ERR(priv->adc_clk) == -ENOENT) {
>> +                     priv->adc_clk = NULL;
>> +             } else {
>> +                     dev_err(&pdev->dev, "failed to get adc clk\n");
>> +                     return PTR_ERR(priv->adc_clk);
>> +             }
>> +     }
>> +
>> +     priv->adc_sel_clk = devm_clk_get(&pdev->dev, "adc_sel");
>> +     if (IS_ERR(priv->adc_sel_clk)) {
>> +             if (PTR_ERR(priv->adc_sel_clk) == -ENOENT) {
>> +                     priv->adc_sel_clk = NULL;
>> +             } else {
>> +                     dev_err(&pdev->dev, "failed to get adc_sel clk\n");
>> +                     return PTR_ERR(priv->adc_sel_clk);
>> +             }
>> +     }
>> +
>> +     /* on pre-GXBB SoCs the SAR ADC itself provides the ADC clock: */
>> +     if (!priv->adc_clk) {
>> +             ret = meson_saradc_clk_init(indio_dev, base);
>> +             if (ret)
>> +                     return ret;
>> +     }
>> +
>> +     priv->vref = devm_regulator_get(&pdev->dev, "vref");
>> +     if (IS_ERR(priv->vref)) {
>> +             dev_err(&pdev->dev, "failed to get vref regulator\n");
>> +             return PTR_ERR(priv->vref);
>> +     }
>> +
>> +     ret = meson_saradc_init(indio_dev);
>> +     if (ret)
>> +             goto err;
>> +
>> +     ret = meson_saradc_hw_enable(indio_dev);
>> +     if (ret)
>> +             goto err;
>> +
>> +     platform_set_drvdata(pdev, indio_dev);
>> +
>> +     indio_dev->name = dev_name(&pdev->dev);
>> +     indio_dev->dev.parent = &pdev->dev;
>> +     indio_dev->dev.of_node = pdev->dev.of_node;
>> +     indio_dev->modes = INDIO_DIRECT_MODE;
>> +     indio_dev->info = &meson_saradc_iio_info;
>> +
>> +     indio_dev->channels = meson_saradc_iio_channels;
>> +     indio_dev->num_channels = SAR_ADC_NUM_CHANNELS;
>> +
>> +     ret = iio_device_register(indio_dev);
>> +     if (ret)
>> +             goto err_hw;
>> +
>> +     return 0;
>> +
>> +err_hw:
>> +     meson_saradc_hw_disable(indio_dev);
>> +err:
>> +     return ret;
>> +}
>> +
>> +static int meson_saradc_remove(struct platform_device *pdev)
>> +{
>> +     struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>> +
>> +     meson_saradc_hw_disable(indio_dev);
>> +     iio_device_unregister(indio_dev);
>> +
>> +     return 0;
>> +}
>> +
>> +#ifdef CONFIG_PM_SLEEP
>> +static int meson_saradc_suspend(struct device *dev)
>> +{
>> +     struct iio_dev *indio_dev = dev_get_drvdata(dev);
>> +
>> +     meson_saradc_hw_disable(indio_dev);
>> +
>> +     return 0;
>> +}
>> +
>> +static int meson_saradc_resume(struct device *dev)
>> +{
>> +     struct iio_dev *indio_dev = dev_get_drvdata(dev);
>> +
>> +     return meson_saradc_hw_enable(indio_dev);
>> +}
>> +#endif /* CONFIG_PM_SLEEP */
>> +
>> +static SIMPLE_DEV_PM_OPS(meson_saradc_pm_ops,
>> +                      meson_saradc_suspend, meson_saradc_resume);
>> +
>> +static struct platform_driver meson_saradc_driver = {
>> +     .probe          = meson_saradc_probe,
>> +     .remove         = meson_saradc_remove,
>> +     .driver         = {
>> +             .name   = "meson-saradc",
>> +             .of_match_table = meson_saradc_of_match,
>> +             .pm = &meson_saradc_pm_ops,
>> +     },
>> +};
>> +
>> +module_platform_driver(meson_saradc_driver);
>> +
>> +MODULE_AUTHOR("Martin Blumenstingl <[e-mail]>");
>> +MODULE_DESCRIPTION("Amlogic Meson SAR ADC driver");
>> +MODULE_LICENSE("GPL v2");
>>
>


Regards,
Martin

[0] http://lists.infradead.org/pipermail/linux-amlogic/2016-August/000986.html

Lars-Peter Clausen Jan. 15, 2017, 12:26 p.m. UTC | #3

On 01/11/2017 06:43 PM, Martin Blumenstingl wrote:
> +	indio_dev->name = dev_name(&pdev->dev);

The name is supposed to be the type of the device, e.g. part name, not the
name of parent device instance. E.g. meson-gxbb-saradc or meson-gxl-saradc
in this case.

Jonathan Cameron Jan. 15, 2017, 1:08 p.m. UTC | #4

On 14/01/17 17:44, Martin Blumenstingl wrote:
> Hi Jonathan,
> 
> thank you for the review!
> (further comments from me inline)
> I think I'll send an updated version on Monday.
> 
> On Sat, Jan 14, 2017 at 3:46 PM, Jonathan Cameron <[e-mail]> wrote:
>> On 11/01/17 17:43, Martin Blumenstingl wrote:
>>> This adds support for the SAR (Successive Approximation Register) ADC
>>> on the Amlogic Meson SoCs.
>>>
>>> The code is based on the public S805 (Meson8b) and S905 (GXBB)
>>> datasheets, as well as by reading (various versions of) the vendor
>>> driver and by inspecting the registers on the vendor kernels of my
>>> testing-hardware.
>>>
>>> Currently the GXBB, GXL and GXM SoCs are supported. GXBB hardware has
>>> 10-bit ADC resolution, while GXL and GXM have 12-bit ADC resolution.
>>> The code was written to support older SoCs (Meson8 and Meson8b) as well,
>>> but due to lack of actual testing-hardware no of_device_id was added for
>>> these.
>>>
>>> Two "features" from the vendor driver are currently missing:
>>> - the vendor driver uses channel #7 for calibration (this improves the
>>>   accuracy of the results - in my tests the results were less than 3%
>>>   off without calibration compared to the vendor driver). Adding support
>>>   for this should be easy, but is not required for most applications.
>>> - channel #6 is connected to the SoCs internal temperature sensor.
>>>   Adding support for this is probably not so easy since (based on the
>>>   u-boot sources) most SoC versions are using different registers and
>>>   algorithms for the conversion from "ADC value" to temperature.
>>>
>>> Supported by the hardware but currently not supported by the driver:
>>> - reading multiple channels at the same time (the hardware has a FIFO
>>>   buffer which stores multiple results)
>>> - continuous sampling (this would require a way to enable this
>>>   individually because otherwise the ADC would be drawing power
>>>   constantly)
>>> - interrupt support (similar to the vendor driver this new driver is
>>>   polling the results. It is unclear if the IRQ-mode is supported on
>>>   older (Meson6 or Meson8) hardware as well or if there are any errata)
>>>
>> Russell Cc'd for a quick question on the clk api.
> a quick side-note the clk API: my driver is a clock consumer and
> provider at the same time. This seems to be a recurring pattern in
> Amlogic hardware designs (as the MMC and DWMAC glue drivers are doing
> this also), see [0]
> 
>> Ideally include a source for datasheets if available. Saves time googling and
>> perhaps getting the wrong thing!
> OK, will do this in v2
> 
>> A few other minor comments inline. Pretty good V1.
> thanks :-)
> 
>> Jonathan
>>> Signed-off-by: Martin Blumenstingl <[e-mail]>
>>> ---
>>>  drivers/iio/adc/Kconfig        |  12 +
>>>  drivers/iio/adc/Makefile       |   1 +
>>>  drivers/iio/adc/meson_saradc.c | 860 +++++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 873 insertions(+)
>>>  create mode 100644 drivers/iio/adc/meson_saradc.c
>>>
>>> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
>>> index 9c8b558ba19e..86059b9b91bf 100644
>>> --- a/drivers/iio/adc/Kconfig
>>> +++ b/drivers/iio/adc/Kconfig
>>> @@ -371,6 +371,18 @@ config MEN_Z188_ADC
>>>         This driver can also be built as a module. If so, the module will be
>>>         called men_z188_adc.
>>>
>>> +config MESON_SARADC
>>> +     tristate "Amlogic Meson SAR ADC driver"
>>> +     default ARCH_MESON
>>> +     depends on OF && COMMON_CLK && (ARCH_MESON || COMPILE_TEST)
>>> +     select REGMAP_MMIO
>>> +     help
>>> +       Say yes here to build support for the SAR ADC found in Amlogic Meson
>>> +       SoCs.
>>> +
>>> +       To compile this driver as a module, choose M here: the
>>> +       module will be called meson_saradc.
>>> +
>>>  config MXS_LRADC
>>>          tristate "Freescale i.MX23/i.MX28 LRADC"
>>>          depends on (ARCH_MXS || COMPILE_TEST) && HAS_IOMEM
>>> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
>>> index d36c4be8d1fc..de05b9e75f8f 100644
>>> --- a/drivers/iio/adc/Makefile
>>> +++ b/drivers/iio/adc/Makefile
>>> @@ -36,6 +36,7 @@ obj-$(CONFIG_MCP320X) += mcp320x.o
>>>  obj-$(CONFIG_MCP3422) += mcp3422.o
>>>  obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
>>>  obj-$(CONFIG_MEN_Z188_ADC) += men_z188_adc.o
>>> +obj-$(CONFIG_MESON_SARADC) += meson_saradc.o
>>>  obj-$(CONFIG_MXS_LRADC) += mxs-lradc.o
>>>  obj-$(CONFIG_NAU7802) += nau7802.o
>>>  obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
>>> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
>>> new file mode 100644
>>> index 000000000000..06e8ac620385
>>> --- /dev/null
>>> +++ b/drivers/iio/adc/meson_saradc.c
>>> @@ -0,0 +1,860 @@
>>> +/*
>>> + * Amlogic Meson Successive Approximation Register (SAR) A/D Converter
>>> + *
>>> + * Copyright (C) 2017 Martin Blumenstingl <[e-mail]>
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + *
>>> + * You should have received a copy of the GNU General Public License
>>> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
>>> + */
>>> +
>>> +#include <linux/bitfield.h>
>>> +#include <linux/clk-provider.h>
>>> +#include <linux/module.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/io.h>
>>> +#include <linux/iio/iio.h>
>>> +#include <linux/of.h>
>>> +#include <linux/of_device.h>
>>> +#include <linux/clk.h>
>>> +#include <linux/completion.h>
>>> +#include <linux/delay.h>
>>> +#include <linux/reset.h>
>>> +#include <linux/regmap.h>
>>> +#include <linux/regulator/consumer.h>
>>> +
>>> +#define SAR_ADC_REG0                                         0x00
>>> +     #define SAR_ADC_REG0_PANEL_DETECT                       BIT(31)
>>> +     #define SAR_ADC_REG0_BUSY_MASK                          GENMASK(30, 28)
>>> +     #define SAR_ADC_REG0_DELTA_BUSY                         BIT(30)
>>> +     #define SAR_ADC_REG0_AVG_BUSY                           BIT(29)
>>> +     #define SAR_ADC_REG0_SAMPLE_BUSY                        BIT(28)
>>> +     #define SAR_ADC_REG0_FIFO_FULL                          BIT(27)
>>> +     #define SAR_ADC_REG0_FIFO_EMPTY                         BIT(26)
>>> +     #define SAR_ADC_REG0_FIFO_COUNT_MASK                    GENMASK(25, 21)
>>> +     #define SAR_ADC_REG0_ADC_BIAS_CTRL_MASK                 GENMASK(20, 19)
>>> +     #define SAR_ADC_REG0_CURR_CHAN_ID_MASK                  GENMASK(18, 16)
>>> +     #define SAR_ADC_REG0_ADC_TEMP_SEN_SEL                   BIT(15)
>>> +     #define SAR_ADC_REG0_SAMPLING_STOP                      BIT(14)
>>> +     #define SAR_ADC_REG0_CHAN_DELTA_EN_MASK                 GENMASK(13, 12)
>>> +     #define SAR_ADC_REG0_DETECT_IRQ_POL                     BIT(10)
>>> +     #define SAR_ADC_REG0_DETECT_IRQ_EN                      BIT(9)
>>> +     #define SAR_ADC_REG0_FIFO_CNT_IRQ_MASK                  GENMASK(8, 4)
>>> +     #define SAR_ADC_REG0_FIFO_IRQ_EN                        BIT(3)
>>> +     #define SAR_ADC_REG0_SAMPLING_START                     BIT(2)
>>> +     #define SAR_ADC_REG0_CONTINUOUS_EN                      BIT(1)
>>> +     #define SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE               BIT(0)
>>> +
>>> +#define SAR_ADC_CHAN_LIST                                    0x04
>>> +     #define SAR_ADC_CHAN_LIST_MAX_INDEX_MASK                GENMASK(26, 24)
>>> +     #define SAR_ADC_CHAN_CHAN_ENTRY_MASK(_chan)             \
>>> +                                     (GENMASK(2, 0) << (_chan * 3))
>>> +
>>> +#define SAR_ADC_AVG_CNTL                                     0x08
>>> +     #define SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(_chan)          \
>>> +                                     (16 + (_chan * 2))
>>> +     #define SAR_ADC_AVG_CNTL_AVG_MODE_MASK(_chan)           \
>>> +                                     (GENMASK(17, 16) << (_chan * 2))
>>> +     #define SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(_chan)       \
>>> +                                     (0 + (_chan * 2))
>>> +     #define SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(_chan)        \
>>> +                                     (GENMASK(1, 0) << (_chan * 2))
>>> +
>>> +#define SAR_ADC_REG3                                         0x0c
>>> +     #define SAR_ADC_REG3_CNTL_USE_SC_DLY                    BIT(31)
>>> +     #define SAR_ADC_REG3_CLK_EN                             BIT(30)
>>> +     #define SAR_ADC_REG3_BL30_INITIALIZED                   BIT(28)
>>> +     #define SAR_ADC_REG3_CTRL_CONT_RING_COUNTER_EN          BIT(27)
>>> +     #define SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE          BIT(26)
>>> +     #define SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK            GENMASK(25, 23)
>>> +     #define SAR_ADC_REG3_DETECT_EN                          BIT(22)
>>> +     #define SAR_ADC_REG3_ADC_EN                             BIT(21)
>>> +     #define SAR_ADC_REG3_PANEL_DETECT_COUNT_MASK            GENMASK(20, 18)
>>> +     #define SAR_ADC_REG3_PANEL_DETECT_FILTER_TB_MASK        GENMASK(17, 16)
>>> +     #define SAR_ADC_REG3_ADC_CLK_DIV_SHIFT                  10
>>> +     #define SAR_ADC_REG3_ADC_CLK_DIV_WIDTH                  5
>>> +     #define SAR_ADC_REG3_ADC_CLK_DIV_MASK                   GENMASK(15, 10)
>>> +     #define SAR_ADC_REG3_BLOCK_DLY_SEL_MASK                 GENMASK(9, 8)
>>> +     #define SAR_ADC_REG3_BLOCK_DLY_MASK                     GENMASK(7, 0)
>>> +
>>> +#define SAR_ADC_DELAY                                                0x10
>>> +     #define SAR_ADC_DELAY_INPUT_DLY_SEL_MASK                GENMASK(25, 24)
>>> +     #define SAR_ADC_DELAY_BL30_BUSY                         BIT(15)
>>> +     #define SAR_ADC_DELAY_KERNEL_BUSY                       BIT(14)
>>> +     #define SAR_ADC_DELAY_INPUT_DLY_CNT_MASK                GENMASK(23, 16)
>>> +     #define SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK               GENMASK(9, 8)
>>> +     #define SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK               GENMASK(7, 0)
>>> +
>>> +#define SAR_ADC_LAST_RD                                              0x14
>>> +     #define SAR_ADC_LAST_RD_LAST_CHANNEL1_MASK              GENMASK(23, 16)
>>> +     #define SAR_ADC_LAST_RD_LAST_CHANNEL0_MASK              GENMASK(9, 0)
>>> +
>>> +#define SAR_ADC_FIFO_RD                                              0x18
>>> +     #define SAR_ADC_FIFO_RD_CHAN_ID_MASK                    GENMASK(14, 12)
>>> +     #define SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK               GENMASK(11, 0)
>>> +
>>> +#define SAR_ADC_AUX_SW                                               0x1c
>>> +     #define SAR_ADC_AUX_SW_MUX_SEL_CHAN_MASK(_chan)         \
>>> +                                     (GENMASK(10, 8) << ((_chan - 2) * 2))
>>> +     #define SAR_ADC_AUX_SW_VREF_P_MUX                       BIT(6)
>>> +     #define SAR_ADC_AUX_SW_VREF_N_MUX                       BIT(5)
>>> +     #define SAR_ADC_AUX_SW_MODE_SEL                         BIT(4)
>>> +     #define SAR_ADC_AUX_SW_YP_DRIVE_SW                      BIT(3)
>>> +     #define SAR_ADC_AUX_SW_XP_DRIVE_SW                      BIT(2)
>>> +     #define SAR_ADC_AUX_SW_YM_DRIVE_SW                      BIT(1)
>>> +     #define SAR_ADC_AUX_SW_XM_DRIVE_SW                      BIT(0)
>>> +
>>> +#define SAR_ADC_CHAN_10_SW                                   0x20
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_MUX_SEL_MASK           GENMASK(25, 23)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_VREF_P_MUX             BIT(22)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_VREF_N_MUX             BIT(21)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_MODE_SEL               BIT(20)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_YP_DRIVE_SW            BIT(19)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_XP_DRIVE_SW            BIT(18)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_YM_DRIVE_SW            BIT(17)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN1_XM_DRIVE_SW            BIT(16)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_MUX_SEL_MASK           GENMASK(9, 7)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_VREF_P_MUX             BIT(6)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_VREF_N_MUX             BIT(5)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_MODE_SEL               BIT(4)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_YP_DRIVE_SW            BIT(3)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_XP_DRIVE_SW            BIT(2)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_YM_DRIVE_SW            BIT(1)
>>> +     #define SAR_ADC_CHAN_10_SW_CHAN0_XM_DRIVE_SW            BIT(0)
>>> +
>>> +#define SAR_ADC_DETECT_IDLE_SW                                       0x24
>>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_SW_EN             BIT(26)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK     GENMASK(25, 23)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_VREF_P_MUX   BIT(22)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_VREF_N_MUX   BIT(21)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_SEL          BIT(20)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_YP_DRIVE_SW  BIT(19)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_XP_DRIVE_SW  BIT(18)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_YM_DRIVE_SW  BIT(17)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_XM_DRIVE_SW  BIT(16)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK   GENMASK(9, 7)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_VREF_P_MUX     BIT(6)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_VREF_N_MUX     BIT(5)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_SEL            BIT(4)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_YP_DRIVE_SW    BIT(3)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_XP_DRIVE_SW    BIT(2)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_YM_DRIVE_SW    BIT(1)
>>> +     #define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_XM_DRIVE_SW    BIT(0)
>>> +
>>> +#define SAR_ADC_DELTA_10                                     0x28
>>> +     #define SAR_ADC_DELTA_10_TEMP_SEL                       BIT(27)
>>> +     #define SAR_ADC_DELTA_10_TS_REVE1                       BIT(26)
>>> +     #define SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_SHIFT        16
>>> +     #define SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_MASK         GENMASK(25, 16)
>>> +     #define SAR_ADC_DELTA_10_TS_REVE0                       BIT(15)
>>> +     #define SAR_ADC_DELTA_10_TS_C_SHIFT                     11
>>> +     #define SAR_ADC_DELTA_10_TS_C_MASK                      GENMASK(14, 11)
>>> +     #define SAR_ADC_DELTA_10_TS_VBG_EN                      BIT(10)
>>> +     #define SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_SHIFT        0
>>> +     #define SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_MASK         GENMASK(9, 0)
>>> +
>>> +/* NOTE: registers from here are undocumented (the vendor Linux kernel driver
>>> + * and u-boot source served as reference). These only seem to be relevant on
>>> + * GXBB and newer.
>>> + */
>>> +#define SAR_ADC_REG11                                                0x2c
>>> +     #define SAR_ADC_REG11_BANDGAP_EN                        BIT(13)
>>> +
>>> +#define SAR_ADC_REG13                                                0x34
>>> +     #define SAR_ADC_REG13_12BIT_CALIBRATION_MASK            GENMASK(13, 8)
>>> +
>>> +#define SAR_ADC_MAX_FIFO_SIZE                32
>>> +#define SAR_ADC_NUM_CHANNELS         ARRAY_SIZE(meson_saradc_iio_channels)
>>> +#define SAR_ADC_VALUE_MASK(_priv)    (BIT(_priv->resolution) - 1)
>>> +
>>> +#define MESON_SAR_ADC_CHAN(_chan, _type) {                           \
>>> +     .type = _type,                                                  \
>>> +     .indexed = true,                                                \
>>> +     .channel = _chan,                                               \
>>> +     .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |                  \
>>> +                             BIT(IIO_CHAN_INFO_AVERAGE_RAW),         \
>>> +     .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),           \
>>> +     .datasheet_name = "SAR_ADC_CH"#_chan,                           \
>>> +}
>>> +
>>> +/* TODO: the hardware supports IIO_TEMP for channel 6 as well which is
>> Multline comment syntax.
> I got this wrong in 2 other places as well. will be fixed in v2, thanks!
> 
>>> + * currently not supported by this driver.
>>> + */
>>> +static const struct iio_chan_spec meson_saradc_iio_channels[] = {
>>> +     MESON_SAR_ADC_CHAN(0, IIO_VOLTAGE),
>>> +     MESON_SAR_ADC_CHAN(1, IIO_VOLTAGE),
>>> +     MESON_SAR_ADC_CHAN(2, IIO_VOLTAGE),
>>> +     MESON_SAR_ADC_CHAN(3, IIO_VOLTAGE),
>>> +     MESON_SAR_ADC_CHAN(4, IIO_VOLTAGE),
>>> +     MESON_SAR_ADC_CHAN(5, IIO_VOLTAGE),
>>> +     MESON_SAR_ADC_CHAN(6, IIO_VOLTAGE),
>>> +     MESON_SAR_ADC_CHAN(7, IIO_VOLTAGE),
>>> +     IIO_CHAN_SOFT_TIMESTAMP(8),
>>> +};
>>> +
>>> +enum meson_saradc_avg_mode {
>>> +     NO_AVERAGING = 0x0,
>>> +     MEAN_AVERAGING = 0x1,
>>> +     MEDIAN_AVERAGING = 0x2,
>>> +};
>>> +
>>> +enum meson_saradc_num_samples {
>>> +     ONE_SAMPLE = 0x0,
>>> +     TWO_SAMPLES = 0x1,
>>> +     FOUR_SAMPLES = 0x2,
>>> +     EIGHT_SAMPLES = 0x3,
>>> +};
>>> +
>>> +enum meson_saradc_chan7_mux_sel {
>>> +     CHAN7_MUX_VSS = 0x0,
>>> +     CHAN7_MUX_VDD_DIV4 = 0x1,
>>> +     CHAN7_MUX_VDD_DIV2 = 0x2,
>>> +     CHAN7_MUX_VDD_MUL3_DIV4 = 0x3,
>>> +     CHAN7_MUX_VDD = 0x4,
>>> +     CHAN7_MUX_CH7_INPUT = 0x7,
>>> +};
>>> +
>>> +struct meson_saradc_priv {
>>> +     struct regmap                   *regmap;
>>> +     struct clk                      *clkin;
>>> +     struct clk                      *core_clk;
>>> +     struct clk                      *sana_clk;
>>> +     struct clk                      *adc_sel_clk;
>>> +     struct clk                      *adc_clk;
>>> +     struct clk_gate                 clk_gate;
>>> +     struct clk                      *adc_div_clk;
>>> +     struct clk_divider              clk_div;
>>> +     struct regulator                *vref;
>>> +     struct completion               completion;
>>> +     u8                              resolution;
>>> +};
>>> +
>>> +static const struct regmap_config meson_saradc_regmap_config = {
>>> +     .reg_bits = 8,
>>> +     .val_bits = 32,
>>> +     .reg_stride = 4,
>>> +     .max_register = SAR_ADC_REG13,
>>> +};
>>> +
>>> +static unsigned int meson_saradc_get_fifo_count(struct iio_dev *indio_dev)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     u32 regval;
>>> +
>>> +     regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
>>> +
>>> +     return FIELD_GET(SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
>>> +}
>>> +
>>> +static int meson_saradc_wait_busy_clear(struct iio_dev *indio_dev)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     int regval, timeout = 10000;
>>> +
>>> +     do {
>>> +             udelay(1);
>>> +             regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
>>> +     } while (FIELD_GET(SAR_ADC_REG0_BUSY_MASK, regval) && timeout--);
>>> +
>>> +     if (timeout < 0)
>>> +             return -ETIMEDOUT;
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int meson_saradc_read_raw_sample(struct iio_dev *indio_dev,
>>> +                                     const struct iio_chan_spec *chan,
>>> +                                     int *val)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     int ret, regval, fifo_chan, fifo_val, sum = 0, count = 0;
>>> +
>>> +     ret = meson_saradc_wait_busy_clear(indio_dev);
>>> +     if (ret)
>>> +             return ret;
>>> +
>>> +     regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
>>> +
>>> +     while (meson_saradc_get_fifo_count(indio_dev) > 0 &&
>>> +            count < SAR_ADC_MAX_FIFO_SIZE) {
>>> +             regmap_read(priv->regmap, SAR_ADC_FIFO_RD, &regval);
>>> +
>>> +             fifo_chan = FIELD_GET(SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
>>> +             if (fifo_chan == chan->channel) {
>>> +                     fifo_val = FIELD_GET(SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK,
>>> +                                          regval) & SAR_ADC_VALUE_MASK(priv);
>>> +                     sum += fifo_val;
>>> +                     count++;
>>> +             }
>>> +     }
>>> +
>>> +     if (!count)
>>> +             return -ENOENT;
>>> +
>>> +     *val = sum / count;
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static void meson_saradc_set_averaging(struct iio_dev *indio_dev,
>>> +                                    const struct iio_chan_spec *chan,
>>> +                                    enum meson_saradc_avg_mode mode,
>>> +                                    enum meson_saradc_num_samples samples)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     u32 val;
>>> +
>>> +     val = samples << SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(chan->channel);
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_AVG_CNTL,
>>> +                        SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(chan->channel),
>>> +                        val);
>>> +
>>> +     val = mode << SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(chan->channel);
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_AVG_CNTL,
>>> +                        SAR_ADC_AVG_CNTL_AVG_MODE_MASK(chan->channel), val);
>>> +}
>>> +
>>> +static void meson_saradc_enable_channel(struct iio_dev *indio_dev,
>>> +                                     const struct iio_chan_spec *chan)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     u32 regval;
>>> +
>>> +     /* the SAR ADC engine allows sampling multiple channels at the same
>>> +      * time. to keep it simple we're only working with one *internal*
>>> +      * channel, which starts counting at index 0 (which means: count = 1).
>>> +      */
>>> +     regval = FIELD_PREP(SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, 0);
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_CHAN_LIST,
>>> +                        SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, regval);
>>> +
>>> +     /* map channel index 0 to the channel which we want to read */
>>> +     regval = FIELD_PREP(SAR_ADC_CHAN_CHAN_ENTRY_MASK(0), chan->channel);
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_CHAN_LIST,
>>> +                        SAR_ADC_CHAN_CHAN_ENTRY_MASK(0), regval);
>>> +
>>> +     regval = FIELD_PREP(SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK,
>>> +                         chan->channel);
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_DETECT_IDLE_SW,
>>> +                        SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK,
>>> +                        regval);
>>> +
>>> +     regval = FIELD_PREP(SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK,
>>> +                         chan->channel);
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_DETECT_IDLE_SW,
>>> +                        SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK,
>>> +                        regval);
>>> +
>>> +     if (chan->channel == 6)
>>> +             regmap_update_bits(priv->regmap, SAR_ADC_DELTA_10,
>>> +                                SAR_ADC_DELTA_10_TEMP_SEL, 0);
>>> +}
>>> +
>>> +static void meson_saradc_set_channel7_mux(struct iio_dev *indio_dev,
>>> +                                       enum meson_saradc_chan7_mux_sel sel)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     u32 regval;
>>> +
>>> +     regval = FIELD_PREP(SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, sel);
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3,
>>> +                        SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, regval);
>>> +
>>> +     usleep_range(10, 20);
>>> +}
>>> +
>>> +static void meson_saradc_start_sample_engine(struct iio_dev *indio_dev)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>>> +                        SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE,
>>> +                        SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE);
>>> +
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>>> +                        SAR_ADC_REG0_SAMPLING_START,
>>> +                        SAR_ADC_REG0_SAMPLING_START);
>>> +}
>>> +
>>> +static void meson_saradc_stop_sample_engine(struct iio_dev *indio_dev)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>>> +                        SAR_ADC_REG0_SAMPLING_STOP,
>>> +                        SAR_ADC_REG0_SAMPLING_STOP);
>>> +
>>> +     /* wait until all modules are stopped */
>>> +     meson_saradc_wait_busy_clear(indio_dev);
>>> +
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>>> +                        SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE, 0);
>>> +}
>>> +
>>> +static void meson_saradc_lock(struct iio_dev *indio_dev)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     int val;
>>> +
>>> +     mutex_lock(&indio_dev->mlock);
>>> +
>>> +     /* prevent BL30 from using the SAR ADC while we are using it */
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>>> +                        SAR_ADC_DELAY_KERNEL_BUSY,
>>> +                        SAR_ADC_DELAY_KERNEL_BUSY);
>>> +
>>> +     /* wait until BL30 releases it's lock (so we can use the SAR ADC) */
>>> +     do {
>>> +             udelay(1);
>>> +             regmap_read(priv->regmap, SAR_ADC_DELAY, &val);
>>> +     } while (val & SAR_ADC_DELAY_BL30_BUSY);
>>> +}
>>> +
>>> +static void meson_saradc_unlock(struct iio_dev *indio_dev)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +
>>> +     /* allow BL30 to use the SAR ADC again */
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>>> +                        SAR_ADC_DELAY_KERNEL_BUSY, 0);
>>> +
>>> +     mutex_unlock(&indio_dev->mlock);
>>> +}
>>> +
>>> +static int meson_saradc_get_sample(struct iio_dev *indio_dev,
>>> +                                const struct iio_chan_spec *chan,
>>> +                                enum meson_saradc_avg_mode avg_mode,
>>> +                                enum meson_saradc_num_samples avg_samples,
>>> +                                int *val)
>>> +{
>>> +     int ret, tmp;
>>> +
>>> +     meson_saradc_lock(indio_dev);
>>> +
>>> +     /* clear old values from the FIFO buffer, ignoring errors */
>>> +     meson_saradc_read_raw_sample(indio_dev, chan, &tmp);
>>> +
>>> +     meson_saradc_set_averaging(indio_dev, chan, avg_mode, avg_samples);
>>> +
>>> +     meson_saradc_enable_channel(indio_dev, chan);
>>> +
>>> +     meson_saradc_start_sample_engine(indio_dev);
>>> +     ret = meson_saradc_read_raw_sample(indio_dev, chan, val);
>>> +     meson_saradc_stop_sample_engine(indio_dev);
>>> +
>>> +     meson_saradc_unlock(indio_dev);
>>> +
>>> +     if (ret) {
>>> +             dev_warn(&indio_dev->dev,
>>> +                      "failed to read sample for channel %d: %d\n",
>>> +                      chan->channel, ret);
>>> +             return ret;
>>> +     }
>>> +
>>> +     return IIO_VAL_INT;
>>> +}
>>> +
>>> +static int meson_saradc_iio_info_read_raw(struct iio_dev *indio_dev,
>>> +                                       const struct iio_chan_spec *chan,
>>> +                                       int *val, int *val2, long mask)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     int ret;
>>> +
>>> +     switch (mask) {
>>> +     case IIO_CHAN_INFO_RAW:
>>> +             return meson_saradc_get_sample(indio_dev, chan, NO_AVERAGING,
>>> +                                            ONE_SAMPLE, val);
>>> +             break;
>>> +
>>> +     case IIO_CHAN_INFO_AVERAGE_RAW:
>>> +             return meson_saradc_get_sample(indio_dev, chan, MEAN_AVERAGING,
>>> +                                            EIGHT_SAMPLES, val);
>>> +             break;
>>> +
>>> +     case IIO_CHAN_INFO_SCALE:
>>> +             ret = regulator_get_voltage(priv->vref);
>>> +             if (ret < 0) {
>>> +                     dev_err(&indio_dev->dev,
>>> +                             "failed to get vref voltage: %d\n", ret);
>>> +                     return ret;
>>> +             }
>>> +
>>> +             *val = ret / 1000;
>>> +             *val2 = priv->resolution;
>>> +             return IIO_VAL_FRACTIONAL_LOG2;
>>> +
>>> +     default:
>>> +             return -EINVAL;
>>> +     }
>>> +}
>>> +
>>> +static int meson_saradc_clk_init(struct iio_dev *indio_dev, void __iomem *base)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     struct clk_init_data init;
>>> +     char clk_name[32];
>>> +     const char *clk_parents[1];
>>> +
>>> +     snprintf(clk_name, sizeof(clk_name), "%s#adc_div",
>>> +              of_node_full_name(indio_dev->dev.of_node));
>>> +     init.name = devm_kstrdup(&indio_dev->dev, clk_name, GFP_KERNEL);
>>> +     init.flags = 0;
>>> +     init.ops = &clk_divider_ops;
>>> +     clk_parents[0] = __clk_get_name(priv->clkin);
>>> +     init.parent_names = clk_parents;
>>> +     init.num_parents = 1;
>>> +
>>> +     priv->clk_div.reg = base + SAR_ADC_REG3;
>>> +     priv->clk_div.shift = SAR_ADC_REG3_ADC_CLK_DIV_SHIFT;
>>> +     priv->clk_div.width = SAR_ADC_REG3_ADC_CLK_DIV_WIDTH;
>>> +     priv->clk_div.hw.init = &init;
>>> +     priv->clk_div.flags = 0;
>>> +
>>> +     priv->adc_div_clk = devm_clk_register(&indio_dev->dev,
>>> +                                           &priv->clk_div.hw);
>>> +     if (WARN_ON(IS_ERR(priv->adc_div_clk)))
>>> +             return PTR_ERR(priv->adc_div_clk);
>>> +
>>> +     snprintf(clk_name, sizeof(clk_name), "%s#adc_en",
>>> +              of_node_full_name(indio_dev->dev.of_node));
>>> +     init.name = devm_kstrdup(&indio_dev->dev, clk_name, GFP_KERNEL);
>>> +     init.flags = CLK_SET_RATE_PARENT;
>>> +     init.ops = &clk_gate_ops;
>>> +     clk_parents[0] = __clk_get_name(priv->adc_div_clk);
>>> +     init.parent_names = clk_parents;
>>> +     init.num_parents = 1;
>>> +
>>> +     priv->clk_gate.reg = base + SAR_ADC_REG3;
>>> +     priv->clk_gate.bit_idx = fls(SAR_ADC_REG3_CLK_EN);
>>> +     priv->clk_gate.hw.init = &init;
>>> +
>>> +     priv->adc_clk = devm_clk_register(&indio_dev->dev, &priv->clk_gate.hw);
>>> +     if (WARN_ON(IS_ERR(priv->adc_clk)))
>>> +             return PTR_ERR(priv->adc_clk);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int meson_saradc_init(struct iio_dev *indio_dev)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     int regval, ret;
>>> +
>>> +     /* make sure we start at CH7 input */
>> why?  Seems like a little more detail would be good here ;)
> I'll change this to "make sure we start at CH7 input since the other
> muxes are only used for internal calibration." in v2
> 
>>> +     meson_saradc_set_channel7_mux(indio_dev, CHAN7_MUX_CH7_INPUT);
>>> +
>>> +     regmap_read(priv->regmap, SAR_ADC_REG3, &regval);
>>> +     if (regval & SAR_ADC_REG3_BL30_INITIALIZED) {
>>> +             dev_info(&indio_dev->dev, "already initialized by BL30\n");
>>> +             return 0;
>>> +     }
>>> +
>>> +     dev_info(&indio_dev->dev, "initializing SAR ADC\n");
>> I'd argue this provides no useful info so should be dropped.
>> Useful for debugging no doubt, but just noise going forward.
> do you want me to remove them or should I turn them into dev_dbg() (so
> they can be enabled for debugging purposes)?
Drop it entirely.
> 
>>> +
>>> +     meson_saradc_stop_sample_engine(indio_dev);
>>> +
>>> +     /* update the channel 6 MUX to select the temperature sensor */
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG0,
>>> +                     SAR_ADC_REG0_ADC_TEMP_SEN_SEL,
>>> +                     SAR_ADC_REG0_ADC_TEMP_SEN_SEL);
>>> +
>>> +     /* disable all channels by default */
>>> +     regmap_write(priv->regmap, SAR_ADC_CHAN_LIST, 0x0);
>>> +
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3,
>>> +                        SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE, 0);
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3,
>>> +                        SAR_ADC_REG3_CNTL_USE_SC_DLY,
>>> +                        SAR_ADC_REG3_CNTL_USE_SC_DLY);
>>> +
>>> +     /* delay between two samples = (10+1) * 1uS */
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>>> +                        SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
>>> +                        FIELD_PREP(SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK, 10));
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>>> +                        SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK,
>>> +                        FIELD_PREP(SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK, 0));
>>> +
>>> +     /* delay between two samples = (10+1) * 1uS */
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>>> +                        SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
>>> +                        FIELD_PREP(SAR_ADC_DELAY_INPUT_DLY_CNT_MASK, 10));
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
>>> +                        SAR_ADC_DELAY_INPUT_DLY_SEL_MASK,
>>> +                        FIELD_PREP(SAR_ADC_DELAY_INPUT_DLY_SEL_MASK, 1));
>>> +
>> Cool. I hadn't come across FIELD_PREP before. Neater and tidier than having
>> a shift and a mask for at least some usecases.
> I think these were introduced with v4.9. I like them because I tend
> use GENMASK() incorrectly and with those macros I get an error at
> compile-time (without having to debug my code at all)
> 
>>> +     ret = clk_set_parent(priv->adc_sel_clk, priv->clkin);
>>> +     if (ret) {
>>> +             dev_err(&indio_dev->dev,
>>> +                     "failed to set adc parent to clkin\n");
>>> +             return ret;
>>> +     }
>>> +
>>> +     ret = clk_set_rate(priv->adc_clk, 1200000);
>>> +     if (ret) {
>>> +             dev_err(&indio_dev->dev, "failed to set adc clock rate\n");
>>> +             return ret;
>>> +     }
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int meson_saradc_hw_enable(struct iio_dev *indio_dev)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +     int ret;
>>> +
>>> +     meson_saradc_lock(indio_dev);
>>> +
>>> +     ret = regulator_enable(priv->vref);
>>> +     if (ret < 0) {
>>> +             dev_err(&indio_dev->dev, "failed to enable vref regulator\n");
>>> +             goto err_vref;
>>> +     }
>>> +
>>> +     ret = clk_prepare_enable(priv->core_clk);
>>> +     if (ret) {
>>> +             dev_err(&indio_dev->dev, "failed to enable core clk\n");
>>> +             goto err_core_clk;
>>> +     }
>>> +
>>> +     ret = clk_prepare_enable(priv->sana_clk);
>>> +     if (ret) {
>>> +             dev_err(&indio_dev->dev, "failed to enable sana clk\n");
>>> +             goto err_sana_clk;
>>> +     }
>>> +
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG11,
>>> +                        SAR_ADC_REG11_BANDGAP_EN, SAR_ADC_REG11_BANDGAP_EN);
>> Is this controlling an offset for a bandgap or some actual electronics?
>> Not sure if it should be disabled on error and the datasheets I've found are
>> far from great!  You disable it in the disable, so I'd expect it to be
>> unwound on error in here too.
> actually the bandgap is not documented at all :(
> 
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3, SAR_ADC_REG3_ADC_EN,
>>> +                        SAR_ADC_REG3_ADC_EN);
>> The fact you turn this of in the disable suggests to me that on error
>> you should be doing it in here too.
> I will disable this along with SAR_ADC_REG11_BANDGAP_EN in the
> err_adc_clk label, thanks for spotting this.
> 
>>> +
>>> +     udelay(5);
>>> +
>>> +     ret = clk_prepare_enable(priv->adc_clk);
>>> +     if (ret) {
>>> +             dev_err(&indio_dev->dev, "failed to enable adc_en clk\n");
>>> +             goto err_adc_clk;
>>> +     }
>>> +
>>> +     meson_saradc_unlock(indio_dev);
>>> +
>>> +     return 0;
>>> +
>>> +err_adc_clk:
>>> +     clk_disable_unprepare(priv->sana_clk);
>>> +err_sana_clk:
>>> +     clk_disable_unprepare(priv->core_clk);
>>> +err_core_clk:
>>> +     regulator_disable(priv->vref);
>>> +err_vref:
>>> +     meson_saradc_unlock(indio_dev);
>>> +     return ret;
>>> +}
>>> +
>>> +static void meson_saradc_hw_disable(struct iio_dev *indio_dev)
>>> +{
>>> +     struct meson_saradc_priv *priv = iio_priv(indio_dev);
>>> +
>>> +     meson_saradc_lock(indio_dev);
>>> +
>>> +     clk_disable_unprepare(priv->adc_clk);
>>> +
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG3, SAR_ADC_REG3_ADC_EN, 0);
>>> +     regmap_update_bits(priv->regmap, SAR_ADC_REG11,
>>> +                        SAR_ADC_REG11_BANDGAP_EN, 0);
>>> +
>>> +     clk_disable_unprepare(priv->sana_clk);
>>> +     clk_disable_unprepare(priv->core_clk);
>>> +
>>> +     regulator_disable(priv->vref);
>>> +
>>> +     meson_saradc_unlock(indio_dev);
>>> +}
>>> +
>>> +static const struct iio_info meson_saradc_iio_info = {
>>> +     .read_raw = meson_saradc_iio_info_read_raw,
>>> +     .driver_module = THIS_MODULE,
>>> +};
>>> +
>>> +static const struct of_device_id meson_saradc_of_match[] = {
>>> +     {
>>> +             .compatible = "amlogic,meson-gxbb-saradc",
>>> +             .data = (void *)10,
>> Might have been worth having a structure array indexed from an enum.
>> For now it is overkill, but seems likely there are a few other differences
>> that aren't supported yet?
> what do you mean with "structure array indexed from an enum"? I can
> introduce some match-specific struct if you want (just like it's done
> in rockchip_saradc.c with "struct rockchip_saradc_data").
That works, or data can be an enum indexing an array of similar structures.
It doesn't really matter.
> 
>>> +     }, {
>>> +             .compatible = "amlogic,meson-gxl-saradc",
>>> +             .data = (void *)12,
>>> +     },
>>> +     {},
>>> +};
>>> +MODULE_DEVICE_TABLE(of, meson_saradc_of_match);
>>> +
>>> +static int meson_saradc_probe(struct platform_device *pdev)
>>> +{
>>> +     struct meson_saradc_priv *priv;
>>> +     struct iio_dev *indio_dev;
>>> +     struct resource *res;
>>> +     void __iomem *base;
>>> +     const struct of_device_id *match;
>>> +     int ret;
>>> +
>>> +     indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
>>> +     if (!indio_dev) {
>>> +             dev_err(&pdev->dev, "failed allocating iio device\n");
>>> +             return -ENOMEM;
>>> +     }
>>> +
>>> +     priv = iio_priv(indio_dev);
>>> +
>>> +     match = of_match_device(meson_saradc_of_match, &pdev->dev);
>>> +     priv->resolution = (unsigned long)match->data;
>>> +
>>> +     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>> +     base = devm_ioremap_resource(&pdev->dev, res);
>>> +     if (IS_ERR(base))
>>> +             return PTR_ERR(base);
>>> +
>>> +     priv->regmap = devm_regmap_init_mmio(&pdev->dev, base,
>>> +                                          &meson_saradc_regmap_config);
>>> +     if (IS_ERR(priv->regmap))
>>> +             return PTR_ERR(priv->regmap);
>>> +
>>> +     init_completion(&priv->completion);
>>> +
>>> +     priv->clkin = devm_clk_get(&pdev->dev, "clkin");
>>> +     if (IS_ERR(priv->clkin)) {
>>> +             dev_err(&pdev->dev, "failed to get clkin\n");
>>> +             return PTR_ERR(priv->clkin);
>>> +     }
>>> +
>>> +     priv->core_clk = devm_clk_get(&pdev->dev, "core");
>>> +     if (IS_ERR(priv->core_clk)) {
>>> +             dev_err(&pdev->dev, "failed to get core clk\n");
>>> +             return PTR_ERR(priv->core_clk);
>>> +     }
>>> +
>>> +     priv->sana_clk = devm_clk_get(&pdev->dev, "sana");
>> Oh for a devm_clk_get_optional to handle this boiler plate neatly.
>> It's been suggested before, but nothing seems to have come of it.
> I guess quite a few drivers would benefit from that. maybe we should
> take this to the linux-clk list again?
Perhaps. I guess this has been proposed before but gone nowhere.
I haven't digged into why though.
> 
>> Some array clk get functions might also clean this up a touch.
> yes, unfortunately in this case it's not that easy as it would have to
> allow a mix of mandatory and optional clocks. Additionally I cannot
> bulk-enable them unconditionally since some of these are simple gates,
> others need to be reparented and for some the rate has to be set.
> 
>>> +     if (IS_ERR(priv->sana_clk)) {
>>> +             if (PTR_ERR(priv->sana_clk) == -ENOENT) {
>>> +                     priv->sana_clk = NULL;
>>> +             } else {
>>> +                     dev_err(&pdev->dev, "failed to get sana clk\n");
>>> +                     return PTR_ERR(priv->sana_clk);
>>> +             }
>>> +     }
>>> +
>>> +     priv->adc_clk = devm_clk_get(&pdev->dev, "adc_clk");
>>> +     if (IS_ERR(priv->adc_clk)) {
>>> +             if (PTR_ERR(priv->adc_clk) == -ENOENT) {
>>> +                     priv->adc_clk = NULL;
>>> +             } else {
>>> +                     dev_err(&pdev->dev, "failed to get adc clk\n");
>>> +                     return PTR_ERR(priv->adc_clk);
>>> +             }
>>> +     }
>>> +
>>> +     priv->adc_sel_clk = devm_clk_get(&pdev->dev, "adc_sel");
>>> +     if (IS_ERR(priv->adc_sel_clk)) {
>>> +             if (PTR_ERR(priv->adc_sel_clk) == -ENOENT) {
>>> +                     priv->adc_sel_clk = NULL;
>>> +             } else {
>>> +                     dev_err(&pdev->dev, "failed to get adc_sel clk\n");
>>> +                     return PTR_ERR(priv->adc_sel_clk);
>>> +             }
>>> +     }
>>> +
>>> +     /* on pre-GXBB SoCs the SAR ADC itself provides the ADC clock: */
>>> +     if (!priv->adc_clk) {
>>> +             ret = meson_saradc_clk_init(indio_dev, base);
>>> +             if (ret)
>>> +                     return ret;
>>> +     }
>>> +
>>> +     priv->vref = devm_regulator_get(&pdev->dev, "vref");
>>> +     if (IS_ERR(priv->vref)) {
>>> +             dev_err(&pdev->dev, "failed to get vref regulator\n");
>>> +             return PTR_ERR(priv->vref);
>>> +     }
>>> +
>>> +     ret = meson_saradc_init(indio_dev);
>>> +     if (ret)
>>> +             goto err;
>>> +
>>> +     ret = meson_saradc_hw_enable(indio_dev);
>>> +     if (ret)
>>> +             goto err;
>>> +
>>> +     platform_set_drvdata(pdev, indio_dev);
>>> +
>>> +     indio_dev->name = dev_name(&pdev->dev);
>>> +     indio_dev->dev.parent = &pdev->dev;
>>> +     indio_dev->dev.of_node = pdev->dev.of_node;
>>> +     indio_dev->modes = INDIO_DIRECT_MODE;
>>> +     indio_dev->info = &meson_saradc_iio_info;
>>> +
>>> +     indio_dev->channels = meson_saradc_iio_channels;
>>> +     indio_dev->num_channels = SAR_ADC_NUM_CHANNELS;
>>> +
>>> +     ret = iio_device_register(indio_dev);
>>> +     if (ret)
>>> +             goto err_hw;
>>> +
>>> +     return 0;
>>> +
>>> +err_hw:
>>> +     meson_saradc_hw_disable(indio_dev);
>>> +err:
>>> +     return ret;
>>> +}
>>> +
>>> +static int meson_saradc_remove(struct platform_device *pdev)
>>> +{
>>> +     struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>>> +
>>> +     meson_saradc_hw_disable(indio_dev);
>>> +     iio_device_unregister(indio_dev);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +#ifdef CONFIG_PM_SLEEP
>>> +static int meson_saradc_suspend(struct device *dev)
>>> +{
>>> +     struct iio_dev *indio_dev = dev_get_drvdata(dev);
>>> +
>>> +     meson_saradc_hw_disable(indio_dev);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int meson_saradc_resume(struct device *dev)
>>> +{
>>> +     struct iio_dev *indio_dev = dev_get_drvdata(dev);
>>> +
>>> +     return meson_saradc_hw_enable(indio_dev);
>>> +}
>>> +#endif /* CONFIG_PM_SLEEP */
>>> +
>>> +static SIMPLE_DEV_PM_OPS(meson_saradc_pm_ops,
>>> +                      meson_saradc_suspend, meson_saradc_resume);
>>> +
>>> +static struct platform_driver meson_saradc_driver = {
>>> +     .probe          = meson_saradc_probe,
>>> +     .remove         = meson_saradc_remove,
>>> +     .driver         = {
>>> +             .name   = "meson-saradc",
>>> +             .of_match_table = meson_saradc_of_match,
>>> +             .pm = &meson_saradc_pm_ops,
>>> +     },
>>> +};
>>> +
>>> +module_platform_driver(meson_saradc_driver);
>>> +
>>> +MODULE_AUTHOR("Martin Blumenstingl <[e-mail]>");
>>> +MODULE_DESCRIPTION("Amlogic Meson SAR ADC driver");
>>> +MODULE_LICENSE("GPL v2");
>>>
>>
> 
> 
> Regards,
> Martin
> 
> [0] http://lists.infradead.org/pipermail/linux-amlogic/2016-August/000986.html
>

Jonathan Cameron Jan. 15, 2017, 1:09 p.m. UTC | #5

On 15/01/17 12:26, Lars-Peter Clausen wrote:
> On 01/11/2017 06:43 PM, Martin Blumenstingl wrote:
>> +	indio_dev->name = dev_name(&pdev->dev);
> 
> The name is supposed to be the type of the device, e.g. part name, not the
> name of parent device instance. E.g. meson-gxbb-saradc or meson-gxl-saradc
> in this case.
Drat. I've been missing these again.  Somehow, never manage to get them
onto those things my eyes pick up whilst reviewing.

Thanks Lars,

Jonathan
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> the body of a message to [e-mail]
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Patch

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 9c8b558ba19e..86059b9b91bf 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -371,6 +371,18 @@  config MEN_Z188_ADC
 	  This driver can also be built as a module. If so, the module will be
 	  called men_z188_adc.
 
+config MESON_SARADC
+	tristate "Amlogic Meson SAR ADC driver"
+	default ARCH_MESON
+	depends on OF && COMMON_CLK && (ARCH_MESON || COMPILE_TEST)
+	select REGMAP_MMIO
+	help
+	  Say yes here to build support for the SAR ADC found in Amlogic Meson
+	  SoCs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called meson_saradc.
+
 config MXS_LRADC
         tristate "Freescale i.MX23/i.MX28 LRADC"
         depends on (ARCH_MXS || COMPILE_TEST) && HAS_IOMEM
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index d36c4be8d1fc..de05b9e75f8f 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -36,6 +36,7 @@  obj-$(CONFIG_MCP320X) += mcp320x.o
 obj-$(CONFIG_MCP3422) += mcp3422.o
 obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
 obj-$(CONFIG_MEN_Z188_ADC) += men_z188_adc.o
+obj-$(CONFIG_MESON_SARADC) += meson_saradc.o
 obj-$(CONFIG_MXS_LRADC) += mxs-lradc.o
 obj-$(CONFIG_NAU7802) += nau7802.o
 obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
new file mode 100644
index 000000000000..06e8ac620385
--- /dev/null
+++ b/drivers/iio/adc/meson_saradc.c
@@ -0,0 +1,860 @@ 
+/*
+ * Amlogic Meson Successive Approximation Register (SAR) A/D Converter
+ *
+ * Copyright (C) 2017 Martin Blumenstingl <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk-provider.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/iio/iio.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/clk.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/reset.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+
+#define SAR_ADC_REG0						0x00
+	#define SAR_ADC_REG0_PANEL_DETECT			BIT(31)
+	#define SAR_ADC_REG0_BUSY_MASK				GENMASK(30, 28)
+	#define SAR_ADC_REG0_DELTA_BUSY				BIT(30)
+	#define SAR_ADC_REG0_AVG_BUSY				BIT(29)
+	#define SAR_ADC_REG0_SAMPLE_BUSY			BIT(28)
+	#define SAR_ADC_REG0_FIFO_FULL				BIT(27)
+	#define SAR_ADC_REG0_FIFO_EMPTY				BIT(26)
+	#define SAR_ADC_REG0_FIFO_COUNT_MASK			GENMASK(25, 21)
+	#define SAR_ADC_REG0_ADC_BIAS_CTRL_MASK			GENMASK(20, 19)
+	#define SAR_ADC_REG0_CURR_CHAN_ID_MASK			GENMASK(18, 16)
+	#define SAR_ADC_REG0_ADC_TEMP_SEN_SEL			BIT(15)
+	#define SAR_ADC_REG0_SAMPLING_STOP			BIT(14)
+	#define SAR_ADC_REG0_CHAN_DELTA_EN_MASK			GENMASK(13, 12)
+	#define SAR_ADC_REG0_DETECT_IRQ_POL			BIT(10)
+	#define SAR_ADC_REG0_DETECT_IRQ_EN			BIT(9)
+	#define SAR_ADC_REG0_FIFO_CNT_IRQ_MASK			GENMASK(8, 4)
+	#define SAR_ADC_REG0_FIFO_IRQ_EN			BIT(3)
+	#define SAR_ADC_REG0_SAMPLING_START			BIT(2)
+	#define SAR_ADC_REG0_CONTINUOUS_EN			BIT(1)
+	#define SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE		BIT(0)
+
+#define SAR_ADC_CHAN_LIST					0x04
+	#define SAR_ADC_CHAN_LIST_MAX_INDEX_MASK		GENMASK(26, 24)
+	#define SAR_ADC_CHAN_CHAN_ENTRY_MASK(_chan)		\
+					(GENMASK(2, 0) << (_chan * 3))
+
+#define SAR_ADC_AVG_CNTL					0x08
+	#define SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(_chan)		\
+					(16 + (_chan * 2))
+	#define SAR_ADC_AVG_CNTL_AVG_MODE_MASK(_chan)		\
+					(GENMASK(17, 16) << (_chan * 2))
+	#define SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(_chan)	\
+					(0 + (_chan * 2))
+	#define SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(_chan)	\
+					(GENMASK(1, 0) << (_chan * 2))
+
+#define SAR_ADC_REG3						0x0c
+	#define SAR_ADC_REG3_CNTL_USE_SC_DLY			BIT(31)
+	#define SAR_ADC_REG3_CLK_EN				BIT(30)
+	#define SAR_ADC_REG3_BL30_INITIALIZED			BIT(28)
+	#define SAR_ADC_REG3_CTRL_CONT_RING_COUNTER_EN		BIT(27)
+	#define SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE		BIT(26)
+	#define SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK		GENMASK(25, 23)
+	#define SAR_ADC_REG3_DETECT_EN				BIT(22)
+	#define SAR_ADC_REG3_ADC_EN				BIT(21)
+	#define SAR_ADC_REG3_PANEL_DETECT_COUNT_MASK		GENMASK(20, 18)
+	#define SAR_ADC_REG3_PANEL_DETECT_FILTER_TB_MASK	GENMASK(17, 16)
+	#define SAR_ADC_REG3_ADC_CLK_DIV_SHIFT			10
+	#define SAR_ADC_REG3_ADC_CLK_DIV_WIDTH			5
+	#define SAR_ADC_REG3_ADC_CLK_DIV_MASK			GENMASK(15, 10)
+	#define SAR_ADC_REG3_BLOCK_DLY_SEL_MASK			GENMASK(9, 8)
+	#define SAR_ADC_REG3_BLOCK_DLY_MASK			GENMASK(7, 0)
+
+#define SAR_ADC_DELAY						0x10
+	#define SAR_ADC_DELAY_INPUT_DLY_SEL_MASK		GENMASK(25, 24)
+	#define SAR_ADC_DELAY_BL30_BUSY				BIT(15)
+	#define SAR_ADC_DELAY_KERNEL_BUSY			BIT(14)
+	#define SAR_ADC_DELAY_INPUT_DLY_CNT_MASK		GENMASK(23, 16)
+	#define SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK		GENMASK(9, 8)
+	#define SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK		GENMASK(7, 0)
+
+#define SAR_ADC_LAST_RD						0x14
+	#define SAR_ADC_LAST_RD_LAST_CHANNEL1_MASK		GENMASK(23, 16)
+	#define SAR_ADC_LAST_RD_LAST_CHANNEL0_MASK		GENMASK(9, 0)
+
+#define SAR_ADC_FIFO_RD						0x18
+	#define SAR_ADC_FIFO_RD_CHAN_ID_MASK			GENMASK(14, 12)
+	#define SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK		GENMASK(11, 0)
+
+#define SAR_ADC_AUX_SW						0x1c
+	#define SAR_ADC_AUX_SW_MUX_SEL_CHAN_MASK(_chan)		\
+					(GENMASK(10, 8) << ((_chan - 2) * 2))
+	#define SAR_ADC_AUX_SW_VREF_P_MUX			BIT(6)
+	#define SAR_ADC_AUX_SW_VREF_N_MUX			BIT(5)
+	#define SAR_ADC_AUX_SW_MODE_SEL				BIT(4)
+	#define SAR_ADC_AUX_SW_YP_DRIVE_SW			BIT(3)
+	#define SAR_ADC_AUX_SW_XP_DRIVE_SW			BIT(2)
+	#define SAR_ADC_AUX_SW_YM_DRIVE_SW			BIT(1)
+	#define SAR_ADC_AUX_SW_XM_DRIVE_SW			BIT(0)
+
+#define SAR_ADC_CHAN_10_SW					0x20
+	#define SAR_ADC_CHAN_10_SW_CHAN1_MUX_SEL_MASK		GENMASK(25, 23)
+	#define SAR_ADC_CHAN_10_SW_CHAN1_VREF_P_MUX		BIT(22)
+	#define SAR_ADC_CHAN_10_SW_CHAN1_VREF_N_MUX		BIT(21)
+	#define SAR_ADC_CHAN_10_SW_CHAN1_MODE_SEL		BIT(20)
+	#define SAR_ADC_CHAN_10_SW_CHAN1_YP_DRIVE_SW		BIT(19)
+	#define SAR_ADC_CHAN_10_SW_CHAN1_XP_DRIVE_SW		BIT(18)
+	#define SAR_ADC_CHAN_10_SW_CHAN1_YM_DRIVE_SW		BIT(17)
+	#define SAR_ADC_CHAN_10_SW_CHAN1_XM_DRIVE_SW		BIT(16)
+	#define SAR_ADC_CHAN_10_SW_CHAN0_MUX_SEL_MASK		GENMASK(9, 7)
+	#define SAR_ADC_CHAN_10_SW_CHAN0_VREF_P_MUX		BIT(6)
+	#define SAR_ADC_CHAN_10_SW_CHAN0_VREF_N_MUX		BIT(5)
+	#define SAR_ADC_CHAN_10_SW_CHAN0_MODE_SEL		BIT(4)
+	#define SAR_ADC_CHAN_10_SW_CHAN0_YP_DRIVE_SW		BIT(3)
+	#define SAR_ADC_CHAN_10_SW_CHAN0_XP_DRIVE_SW		BIT(2)
+	#define SAR_ADC_CHAN_10_SW_CHAN0_YM_DRIVE_SW		BIT(1)
+	#define SAR_ADC_CHAN_10_SW_CHAN0_XM_DRIVE_SW		BIT(0)
+
+#define SAR_ADC_DETECT_IDLE_SW					0x24
+	#define SAR_ADC_DETECT_IDLE_SW_DETECT_SW_EN		BIT(26)
+	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK	GENMASK(25, 23)
+	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_VREF_P_MUX	BIT(22)
+	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_VREF_N_MUX	BIT(21)
+	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_SEL		BIT(20)
+	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_YP_DRIVE_SW	BIT(19)
+	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_XP_DRIVE_SW	BIT(18)
+	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_YM_DRIVE_SW	BIT(17)
+	#define SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_XM_DRIVE_SW	BIT(16)
+	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK	GENMASK(9, 7)
+	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_VREF_P_MUX	BIT(6)
+	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_VREF_N_MUX	BIT(5)
+	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_SEL		BIT(4)
+	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_YP_DRIVE_SW	BIT(3)
+	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_XP_DRIVE_SW	BIT(2)
+	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_YM_DRIVE_SW	BIT(1)
+	#define SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_XM_DRIVE_SW	BIT(0)
+
+#define SAR_ADC_DELTA_10					0x28
+	#define SAR_ADC_DELTA_10_TEMP_SEL			BIT(27)
+	#define SAR_ADC_DELTA_10_TS_REVE1			BIT(26)
+	#define SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_SHIFT	16
+	#define SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_MASK		GENMASK(25, 16)
+	#define SAR_ADC_DELTA_10_TS_REVE0			BIT(15)
+	#define SAR_ADC_DELTA_10_TS_C_SHIFT			11
+	#define SAR_ADC_DELTA_10_TS_C_MASK			GENMASK(14, 11)
+	#define SAR_ADC_DELTA_10_TS_VBG_EN			BIT(10)
+	#define SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_SHIFT	0
+	#define SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_MASK		GENMASK(9, 0)
+
+/* NOTE: registers from here are undocumented (the vendor Linux kernel driver
+ * and u-boot source served as reference). These only seem to be relevant on
+ * GXBB and newer.
+ */
+#define SAR_ADC_REG11						0x2c
+	#define SAR_ADC_REG11_BANDGAP_EN			BIT(13)
+
+#define SAR_ADC_REG13						0x34
+	#define SAR_ADC_REG13_12BIT_CALIBRATION_MASK		GENMASK(13, 8)
+
+#define SAR_ADC_MAX_FIFO_SIZE		32
+#define SAR_ADC_NUM_CHANNELS		ARRAY_SIZE(meson_saradc_iio_channels)
+#define SAR_ADC_VALUE_MASK(_priv)	(BIT(_priv->resolution) - 1)
+
+#define MESON_SAR_ADC_CHAN(_chan, _type) {				\
+	.type = _type,							\
+	.indexed = true,						\
+	.channel = _chan,						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
+				BIT(IIO_CHAN_INFO_AVERAGE_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
+	.datasheet_name = "SAR_ADC_CH"#_chan,				\
+}
+
+/* TODO: the hardware supports IIO_TEMP for channel 6 as well which is
+ * currently not supported by this driver.
+ */
+static const struct iio_chan_spec meson_saradc_iio_channels[] = {
+	MESON_SAR_ADC_CHAN(0, IIO_VOLTAGE),
+	MESON_SAR_ADC_CHAN(1, IIO_VOLTAGE),
+	MESON_SAR_ADC_CHAN(2, IIO_VOLTAGE),
+	MESON_SAR_ADC_CHAN(3, IIO_VOLTAGE),
+	MESON_SAR_ADC_CHAN(4, IIO_VOLTAGE),
+	MESON_SAR_ADC_CHAN(5, IIO_VOLTAGE),
+	MESON_SAR_ADC_CHAN(6, IIO_VOLTAGE),
+	MESON_SAR_ADC_CHAN(7, IIO_VOLTAGE),
+	IIO_CHAN_SOFT_TIMESTAMP(8),
+};
+
+enum meson_saradc_avg_mode {
+	NO_AVERAGING = 0x0,
+	MEAN_AVERAGING = 0x1,
+	MEDIAN_AVERAGING = 0x2,
+};
+
+enum meson_saradc_num_samples {
+	ONE_SAMPLE = 0x0,
+	TWO_SAMPLES = 0x1,
+	FOUR_SAMPLES = 0x2,
+	EIGHT_SAMPLES = 0x3,
+};
+
+enum meson_saradc_chan7_mux_sel {
+	CHAN7_MUX_VSS = 0x0,
+	CHAN7_MUX_VDD_DIV4 = 0x1,
+	CHAN7_MUX_VDD_DIV2 = 0x2,
+	CHAN7_MUX_VDD_MUL3_DIV4 = 0x3,
+	CHAN7_MUX_VDD = 0x4,
+	CHAN7_MUX_CH7_INPUT = 0x7,
+};
+
+struct meson_saradc_priv {
+	struct regmap			*regmap;
+	struct clk			*clkin;
+	struct clk			*core_clk;
+	struct clk			*sana_clk;
+	struct clk			*adc_sel_clk;
+	struct clk			*adc_clk;
+	struct clk_gate			clk_gate;
+	struct clk			*adc_div_clk;
+	struct clk_divider		clk_div;
+	struct regulator		*vref;
+	struct completion		completion;
+	u8				resolution;
+};
+
+static const struct regmap_config meson_saradc_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 32,
+	.reg_stride = 4,
+	.max_register = SAR_ADC_REG13,
+};
+
+static unsigned int meson_saradc_get_fifo_count(struct iio_dev *indio_dev)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	u32 regval;
+
+	regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
+
+	return FIELD_GET(SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
+}
+
+static int meson_saradc_wait_busy_clear(struct iio_dev *indio_dev)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	int regval, timeout = 10000;
+
+	do {
+		udelay(1);
+		regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
+	} while (FIELD_GET(SAR_ADC_REG0_BUSY_MASK, regval) && timeout--);
+
+	if (timeout < 0)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+static int meson_saradc_read_raw_sample(struct iio_dev *indio_dev,
+					const struct iio_chan_spec *chan,
+					int *val)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	int ret, regval, fifo_chan, fifo_val, sum = 0, count = 0;
+
+	ret = meson_saradc_wait_busy_clear(indio_dev);
+	if (ret)
+		return ret;
+
+	regmap_read(priv->regmap, SAR_ADC_REG0, &regval);
+
+	while (meson_saradc_get_fifo_count(indio_dev) > 0 &&
+	       count < SAR_ADC_MAX_FIFO_SIZE) {
+		regmap_read(priv->regmap, SAR_ADC_FIFO_RD, &regval);
+
+		fifo_chan = FIELD_GET(SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
+		if (fifo_chan == chan->channel) {
+			fifo_val = FIELD_GET(SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK,
+					     regval) & SAR_ADC_VALUE_MASK(priv);
+			sum += fifo_val;
+			count++;
+		}
+	}
+
+	if (!count)
+		return -ENOENT;
+
+	*val = sum / count;
+
+	return 0;
+}
+
+static void meson_saradc_set_averaging(struct iio_dev *indio_dev,
+				       const struct iio_chan_spec *chan,
+				       enum meson_saradc_avg_mode mode,
+				       enum meson_saradc_num_samples samples)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	u32 val;
+
+	val = samples << SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(chan->channel);
+	regmap_update_bits(priv->regmap, SAR_ADC_AVG_CNTL,
+			   SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(chan->channel),
+			   val);
+
+	val = mode << SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(chan->channel);
+	regmap_update_bits(priv->regmap, SAR_ADC_AVG_CNTL,
+			   SAR_ADC_AVG_CNTL_AVG_MODE_MASK(chan->channel), val);
+}
+
+static void meson_saradc_enable_channel(struct iio_dev *indio_dev,
+					const struct iio_chan_spec *chan)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	u32 regval;
+
+	/* the SAR ADC engine allows sampling multiple channels at the same
+	 * time. to keep it simple we're only working with one *internal*
+	 * channel, which starts counting at index 0 (which means: count = 1).
+	 */
+	regval = FIELD_PREP(SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, 0);
+	regmap_update_bits(priv->regmap, SAR_ADC_CHAN_LIST,
+			   SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, regval);
+
+	/* map channel index 0 to the channel which we want to read */
+	regval = FIELD_PREP(SAR_ADC_CHAN_CHAN_ENTRY_MASK(0), chan->channel);
+	regmap_update_bits(priv->regmap, SAR_ADC_CHAN_LIST,
+			   SAR_ADC_CHAN_CHAN_ENTRY_MASK(0), regval);
+
+	regval = FIELD_PREP(SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK,
+			    chan->channel);
+	regmap_update_bits(priv->regmap, SAR_ADC_DETECT_IDLE_SW,
+			   SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_MUX_MASK,
+			   regval);
+
+	regval = FIELD_PREP(SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK,
+			    chan->channel);
+	regmap_update_bits(priv->regmap, SAR_ADC_DETECT_IDLE_SW,
+			   SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_MUX_SEL_MASK,
+			   regval);
+
+	if (chan->channel == 6)
+		regmap_update_bits(priv->regmap, SAR_ADC_DELTA_10,
+				   SAR_ADC_DELTA_10_TEMP_SEL, 0);
+}
+
+static void meson_saradc_set_channel7_mux(struct iio_dev *indio_dev,
+					  enum meson_saradc_chan7_mux_sel sel)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	u32 regval;
+
+	regval = FIELD_PREP(SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, sel);
+	regmap_update_bits(priv->regmap, SAR_ADC_REG3,
+			   SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, regval);
+
+	usleep_range(10, 20);
+}
+
+static void meson_saradc_start_sample_engine(struct iio_dev *indio_dev)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+
+	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
+			   SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE,
+			   SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE);
+
+	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
+			   SAR_ADC_REG0_SAMPLING_START,
+			   SAR_ADC_REG0_SAMPLING_START);
+}
+
+static void meson_saradc_stop_sample_engine(struct iio_dev *indio_dev)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+
+	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
+			   SAR_ADC_REG0_SAMPLING_STOP,
+			   SAR_ADC_REG0_SAMPLING_STOP);
+
+	/* wait until all modules are stopped */
+	meson_saradc_wait_busy_clear(indio_dev);
+
+	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
+			   SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE, 0);
+}
+
+static void meson_saradc_lock(struct iio_dev *indio_dev)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	int val;
+
+	mutex_lock(&indio_dev->mlock);
+
+	/* prevent BL30 from using the SAR ADC while we are using it */
+	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
+			   SAR_ADC_DELAY_KERNEL_BUSY,
+			   SAR_ADC_DELAY_KERNEL_BUSY);
+
+	/* wait until BL30 releases it's lock (so we can use the SAR ADC) */
+	do {
+		udelay(1);
+		regmap_read(priv->regmap, SAR_ADC_DELAY, &val);
+	} while (val & SAR_ADC_DELAY_BL30_BUSY);
+}
+
+static void meson_saradc_unlock(struct iio_dev *indio_dev)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+
+	/* allow BL30 to use the SAR ADC again */
+	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
+			   SAR_ADC_DELAY_KERNEL_BUSY, 0);
+
+	mutex_unlock(&indio_dev->mlock);
+}
+
+static int meson_saradc_get_sample(struct iio_dev *indio_dev,
+				   const struct iio_chan_spec *chan,
+				   enum meson_saradc_avg_mode avg_mode,
+				   enum meson_saradc_num_samples avg_samples,
+				   int *val)
+{
+	int ret, tmp;
+
+	meson_saradc_lock(indio_dev);
+
+	/* clear old values from the FIFO buffer, ignoring errors */
+	meson_saradc_read_raw_sample(indio_dev, chan, &tmp);
+
+	meson_saradc_set_averaging(indio_dev, chan, avg_mode, avg_samples);
+
+	meson_saradc_enable_channel(indio_dev, chan);
+
+	meson_saradc_start_sample_engine(indio_dev);
+	ret = meson_saradc_read_raw_sample(indio_dev, chan, val);
+	meson_saradc_stop_sample_engine(indio_dev);
+
+	meson_saradc_unlock(indio_dev);
+
+	if (ret) {
+		dev_warn(&indio_dev->dev,
+			 "failed to read sample for channel %d: %d\n",
+			 chan->channel, ret);
+		return ret;
+	}
+
+	return IIO_VAL_INT;
+}
+
+static int meson_saradc_iio_info_read_raw(struct iio_dev *indio_dev,
+					  const struct iio_chan_spec *chan,
+					  int *val, int *val2, long mask)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		return meson_saradc_get_sample(indio_dev, chan, NO_AVERAGING,
+					       ONE_SAMPLE, val);
+		break;
+
+	case IIO_CHAN_INFO_AVERAGE_RAW:
+		return meson_saradc_get_sample(indio_dev, chan, MEAN_AVERAGING,
+					       EIGHT_SAMPLES, val);
+		break;
+
+	case IIO_CHAN_INFO_SCALE:
+		ret = regulator_get_voltage(priv->vref);
+		if (ret < 0) {
+			dev_err(&indio_dev->dev,
+				"failed to get vref voltage: %d\n", ret);
+			return ret;
+		}
+
+		*val = ret / 1000;
+		*val2 = priv->resolution;
+		return IIO_VAL_FRACTIONAL_LOG2;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int meson_saradc_clk_init(struct iio_dev *indio_dev, void __iomem *base)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	struct clk_init_data init;
+	char clk_name[32];
+	const char *clk_parents[1];
+
+	snprintf(clk_name, sizeof(clk_name), "%s#adc_div",
+		 of_node_full_name(indio_dev->dev.of_node));
+	init.name = devm_kstrdup(&indio_dev->dev, clk_name, GFP_KERNEL);
+	init.flags = 0;
+	init.ops = &clk_divider_ops;
+	clk_parents[0] = __clk_get_name(priv->clkin);
+	init.parent_names = clk_parents;
+	init.num_parents = 1;
+
+	priv->clk_div.reg = base + SAR_ADC_REG3;
+	priv->clk_div.shift = SAR_ADC_REG3_ADC_CLK_DIV_SHIFT;
+	priv->clk_div.width = SAR_ADC_REG3_ADC_CLK_DIV_WIDTH;
+	priv->clk_div.hw.init = &init;
+	priv->clk_div.flags = 0;
+
+	priv->adc_div_clk = devm_clk_register(&indio_dev->dev,
+					      &priv->clk_div.hw);
+	if (WARN_ON(IS_ERR(priv->adc_div_clk)))
+		return PTR_ERR(priv->adc_div_clk);
+
+	snprintf(clk_name, sizeof(clk_name), "%s#adc_en",
+		 of_node_full_name(indio_dev->dev.of_node));
+	init.name = devm_kstrdup(&indio_dev->dev, clk_name, GFP_KERNEL);
+	init.flags = CLK_SET_RATE_PARENT;
+	init.ops = &clk_gate_ops;
+	clk_parents[0] = __clk_get_name(priv->adc_div_clk);
+	init.parent_names = clk_parents;
+	init.num_parents = 1;
+
+	priv->clk_gate.reg = base + SAR_ADC_REG3;
+	priv->clk_gate.bit_idx = fls(SAR_ADC_REG3_CLK_EN);
+	priv->clk_gate.hw.init = &init;
+
+	priv->adc_clk = devm_clk_register(&indio_dev->dev, &priv->clk_gate.hw);
+	if (WARN_ON(IS_ERR(priv->adc_clk)))
+		return PTR_ERR(priv->adc_clk);
+
+	return 0;
+}
+
+static int meson_saradc_init(struct iio_dev *indio_dev)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	int regval, ret;
+
+	/* make sure we start at CH7 input */
+	meson_saradc_set_channel7_mux(indio_dev, CHAN7_MUX_CH7_INPUT);
+
+	regmap_read(priv->regmap, SAR_ADC_REG3, &regval);
+	if (regval & SAR_ADC_REG3_BL30_INITIALIZED) {
+		dev_info(&indio_dev->dev, "already initialized by BL30\n");
+		return 0;
+	}
+
+	dev_info(&indio_dev->dev, "initializing SAR ADC\n");
+
+	meson_saradc_stop_sample_engine(indio_dev);
+
+	/* update the channel 6 MUX to select the temperature sensor */
+	regmap_update_bits(priv->regmap, SAR_ADC_REG0,
+			SAR_ADC_REG0_ADC_TEMP_SEN_SEL,
+			SAR_ADC_REG0_ADC_TEMP_SEN_SEL);
+
+	/* disable all channels by default */
+	regmap_write(priv->regmap, SAR_ADC_CHAN_LIST, 0x0);
+
+	regmap_update_bits(priv->regmap, SAR_ADC_REG3,
+			   SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE, 0);
+	regmap_update_bits(priv->regmap, SAR_ADC_REG3,
+			   SAR_ADC_REG3_CNTL_USE_SC_DLY,
+			   SAR_ADC_REG3_CNTL_USE_SC_DLY);
+
+	/* delay between two samples = (10+1) * 1uS */
+	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
+			   SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
+			   FIELD_PREP(SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK, 10));
+	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
+			   SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK,
+			   FIELD_PREP(SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK, 0));
+
+	/* delay between two samples = (10+1) * 1uS */
+	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
+			   SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
+			   FIELD_PREP(SAR_ADC_DELAY_INPUT_DLY_CNT_MASK, 10));
+	regmap_update_bits(priv->regmap, SAR_ADC_DELAY,
+			   SAR_ADC_DELAY_INPUT_DLY_SEL_MASK,
+			   FIELD_PREP(SAR_ADC_DELAY_INPUT_DLY_SEL_MASK, 1));
+
+	ret = clk_set_parent(priv->adc_sel_clk, priv->clkin);
+	if (ret) {
+		dev_err(&indio_dev->dev,
+			"failed to set adc parent to clkin\n");
+		return ret;
+	}
+
+	ret = clk_set_rate(priv->adc_clk, 1200000);
+	if (ret) {
+		dev_err(&indio_dev->dev, "failed to set adc clock rate\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int meson_saradc_hw_enable(struct iio_dev *indio_dev)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+	int ret;
+
+	meson_saradc_lock(indio_dev);
+
+	ret = regulator_enable(priv->vref);
+	if (ret < 0) {
+		dev_err(&indio_dev->dev, "failed to enable vref regulator\n");
+		goto err_vref;
+	}
+
+	ret = clk_prepare_enable(priv->core_clk);
+	if (ret) {
+		dev_err(&indio_dev->dev, "failed to enable core clk\n");
+		goto err_core_clk;
+	}
+
+	ret = clk_prepare_enable(priv->sana_clk);
+	if (ret) {
+		dev_err(&indio_dev->dev, "failed to enable sana clk\n");
+		goto err_sana_clk;
+	}
+
+	regmap_update_bits(priv->regmap, SAR_ADC_REG11,
+			   SAR_ADC_REG11_BANDGAP_EN, SAR_ADC_REG11_BANDGAP_EN);
+	regmap_update_bits(priv->regmap, SAR_ADC_REG3, SAR_ADC_REG3_ADC_EN,
+			   SAR_ADC_REG3_ADC_EN);
+
+	udelay(5);
+
+	ret = clk_prepare_enable(priv->adc_clk);
+	if (ret) {
+		dev_err(&indio_dev->dev, "failed to enable adc_en clk\n");
+		goto err_adc_clk;
+	}
+
+	meson_saradc_unlock(indio_dev);
+
+	return 0;
+
+err_adc_clk:
+	clk_disable_unprepare(priv->sana_clk);
+err_sana_clk:
+	clk_disable_unprepare(priv->core_clk);
+err_core_clk:
+	regulator_disable(priv->vref);
+err_vref:
+	meson_saradc_unlock(indio_dev);
+	return ret;
+}
+
+static void meson_saradc_hw_disable(struct iio_dev *indio_dev)
+{
+	struct meson_saradc_priv *priv = iio_priv(indio_dev);
+
+	meson_saradc_lock(indio_dev);
+
+	clk_disable_unprepare(priv->adc_clk);
+
+	regmap_update_bits(priv->regmap, SAR_ADC_REG3, SAR_ADC_REG3_ADC_EN, 0);
+	regmap_update_bits(priv->regmap, SAR_ADC_REG11,
+			   SAR_ADC_REG11_BANDGAP_EN, 0);
+
+	clk_disable_unprepare(priv->sana_clk);
+	clk_disable_unprepare(priv->core_clk);
+
+	regulator_disable(priv->vref);
+
+	meson_saradc_unlock(indio_dev);
+}
+
+static const struct iio_info meson_saradc_iio_info = {
+	.read_raw = meson_saradc_iio_info_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static const struct of_device_id meson_saradc_of_match[] = {
+	{
+		.compatible = "amlogic,meson-gxbb-saradc",
+		.data = (void *)10,
+	}, {
+		.compatible = "amlogic,meson-gxl-saradc",
+		.data = (void *)12,
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, meson_saradc_of_match);
+
+static int meson_saradc_probe(struct platform_device *pdev)
+{
+	struct meson_saradc_priv *priv;
+	struct iio_dev *indio_dev;
+	struct resource *res;
+	void __iomem *base;
+	const struct of_device_id *match;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
+	if (!indio_dev) {
+		dev_err(&pdev->dev, "failed allocating iio device\n");
+		return -ENOMEM;
+	}
+
+	priv = iio_priv(indio_dev);
+
+	match = of_match_device(meson_saradc_of_match, &pdev->dev);
+	priv->resolution = (unsigned long)match->data;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	priv->regmap = devm_regmap_init_mmio(&pdev->dev, base,
+					     &meson_saradc_regmap_config);
+	if (IS_ERR(priv->regmap))
+		return PTR_ERR(priv->regmap);
+
+	init_completion(&priv->completion);
+
+	priv->clkin = devm_clk_get(&pdev->dev, "clkin");
+	if (IS_ERR(priv->clkin)) {
+		dev_err(&pdev->dev, "failed to get clkin\n");
+		return PTR_ERR(priv->clkin);
+	}
+
+	priv->core_clk = devm_clk_get(&pdev->dev, "core");
+	if (IS_ERR(priv->core_clk)) {
+		dev_err(&pdev->dev, "failed to get core clk\n");
+		return PTR_ERR(priv->core_clk);
+	}
+
+	priv->sana_clk = devm_clk_get(&pdev->dev, "sana");
+	if (IS_ERR(priv->sana_clk)) {
+		if (PTR_ERR(priv->sana_clk) == -ENOENT) {
+			priv->sana_clk = NULL;
+		} else {
+			dev_err(&pdev->dev, "failed to get sana clk\n");
+			return PTR_ERR(priv->sana_clk);
+		}
+	}
+
+	priv->adc_clk = devm_clk_get(&pdev->dev, "adc_clk");
+	if (IS_ERR(priv->adc_clk)) {
+		if (PTR_ERR(priv->adc_clk) == -ENOENT) {
+			priv->adc_clk = NULL;
+		} else {
+			dev_err(&pdev->dev, "failed to get adc clk\n");
+			return PTR_ERR(priv->adc_clk);
+		}
+	}
+
+	priv->adc_sel_clk = devm_clk_get(&pdev->dev, "adc_sel");
+	if (IS_ERR(priv->adc_sel_clk)) {
+		if (PTR_ERR(priv->adc_sel_clk) == -ENOENT) {
+			priv->adc_sel_clk = NULL;
+		} else {
+			dev_err(&pdev->dev, "failed to get adc_sel clk\n");
+			return PTR_ERR(priv->adc_sel_clk);
+		}
+	}
+
+	/* on pre-GXBB SoCs the SAR ADC itself provides the ADC clock: */
+	if (!priv->adc_clk) {
+		ret = meson_saradc_clk_init(indio_dev, base);
+		if (ret)
+			return ret;
+	}
+
+	priv->vref = devm_regulator_get(&pdev->dev, "vref");
+	if (IS_ERR(priv->vref)) {
+		dev_err(&pdev->dev, "failed to get vref regulator\n");
+		return PTR_ERR(priv->vref);
+	}
+
+	ret = meson_saradc_init(indio_dev);
+	if (ret)
+		goto err;
+
+	ret = meson_saradc_hw_enable(indio_dev);
+	if (ret)
+		goto err;
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	indio_dev->name = dev_name(&pdev->dev);
+	indio_dev->dev.parent = &pdev->dev;
+	indio_dev->dev.of_node = pdev->dev.of_node;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &meson_saradc_iio_info;
+
+	indio_dev->channels = meson_saradc_iio_channels;
+	indio_dev->num_channels = SAR_ADC_NUM_CHANNELS;
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto err_hw;
+
+	return 0;
+
+err_hw:
+	meson_saradc_hw_disable(indio_dev);
+err:
+	return ret;
+}
+
+static int meson_saradc_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+
+	meson_saradc_hw_disable(indio_dev);
+	iio_device_unregister(indio_dev);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int meson_saradc_suspend(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+
+	meson_saradc_hw_disable(indio_dev);
+
+	return 0;
+}
+
+static int meson_saradc_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+
+	return meson_saradc_hw_enable(indio_dev);
+}
+#endif /* CONFIG_PM_SLEEP */
+
+static SIMPLE_DEV_PM_OPS(meson_saradc_pm_ops,
+			 meson_saradc_suspend, meson_saradc_resume);
+
+static struct platform_driver meson_saradc_driver = {
+	.probe		= meson_saradc_probe,
+	.remove		= meson_saradc_remove,
+	.driver		= {
+		.name	= "meson-saradc",
+		.of_match_table = meson_saradc_of_match,
+		.pm = &meson_saradc_pm_ops,
+	},
+};
+
+module_platform_driver(meson_saradc_driver);
+
+MODULE_AUTHOR("Martin Blumenstingl <[e-mail]>");
+MODULE_DESCRIPTION("Amlogic Meson SAR ADC driver");
+MODULE_LICENSE("GPL v2");