diff mbox series

[v4,1/3] iio: dac: add support for ltc2688

Message ID 20220225130129.69-2-nuno.sa@analog.com (mailing list archive)
State Accepted
Headers show
Series Add support for LTC2688 | expand

Commit Message

Nuno Sá Feb. 25, 2022, 1:01 p.m. UTC
The LTC2688 is a 16 channel, 16 bit, +-15V DAC with an integrated
precision reference. It is guaranteed monotonic and has built in
rail-to-rail output buffers that can source or sink up to 20 mA.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
---
 MAINTAINERS               |    7 +
 drivers/iio/dac/Kconfig   |   11 +
 drivers/iio/dac/Makefile  |    1 +
 drivers/iio/dac/ltc2688.c | 1071 +++++++++++++++++++++++++++++++++++++
 4 files changed, 1090 insertions(+)
 create mode 100644 drivers/iio/dac/ltc2688.c

Comments

Jonathan Cameron Feb. 27, 2022, 12:38 p.m. UTC | #1
On Fri, 25 Feb 2022 14:01:27 +0100
Nuno Sá <nuno.sa@analog.com> wrote:

> The LTC2688 is a 16 channel, 16 bit, +-15V DAC with an integrated
> precision reference. It is guaranteed monotonic and has built in
> rail-to-rail output buffers that can source or sink up to 20 mA.
> 
> Signed-off-by: Nuno Sá <nuno.sa@analog.com>

Just one comment below - not a suggestion to change anything at this
stage though, just something that might come up in future.


...

> +static const char * const ltc2688_dither_phase[] = {
> +	"0", "1.5708", "3.14159", "4.71239",
> +};
> +

It if turns out we have in kernel users for this in the long run
we may need to change these over to numeric values, but we
can do that without changing the userspace ABI, so this is fine for
now.

...


Thanks,

Jonathan
diff mbox series

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index 96e9243f0242..6fc957727094 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11309,6 +11309,13 @@  S:	Maintained
 F:	Documentation/devicetree/bindings/iio/dac/lltc,ltc1660.yaml
 F:	drivers/iio/dac/ltc1660.c
 
+LTC2688 IIO DAC DRIVER
+M:	Nuno Sá <nuno.sa@analog.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+W:	http://ez.analog.com/community/linux-device-drivers
+F:	drivers/iio/dac/ltc2688.c
+
 LTC2947 HARDWARE MONITOR DRIVER
 M:	Nuno Sá <nuno.sa@analog.com>
 L:	linux-hwmon@vger.kernel.org
diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index bfcf7568de32..c0bf0d84197f 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -131,6 +131,17 @@  config AD5624R_SPI
 	  Say yes here to build support for Analog Devices AD5624R, AD5644R and
 	  AD5664R converters (DAC). This driver uses the common SPI interface.
 
+config LTC2688
+	tristate "Analog Devices LTC2688 DAC spi driver"
+	depends on SPI
+	select REGMAP
+	help
+	  Say yes here to build support for Analog Devices
+	  LTC2688 converters (DAC).
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ltc2688.
+
 config AD5686
 	tristate
 
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 01a50131572f..ec3e42713f00 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -35,6 +35,7 @@  obj-$(CONFIG_DS4424) += ds4424.o
 obj-$(CONFIG_LPC18XX_DAC) += lpc18xx_dac.o
 obj-$(CONFIG_LTC1660) += ltc1660.o
 obj-$(CONFIG_LTC2632) += ltc2632.o
+obj-$(CONFIG_LTC2688) += ltc2688.o
 obj-$(CONFIG_M62332) += m62332.o
 obj-$(CONFIG_MAX517) += max517.o
 obj-$(CONFIG_MAX5821) += max5821.o
diff --git a/drivers/iio/dac/ltc2688.c b/drivers/iio/dac/ltc2688.c
new file mode 100644
index 000000000000..e41861d29767
--- /dev/null
+++ b/drivers/iio/dac/ltc2688.c
@@ -0,0 +1,1071 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LTC2688 16 channel, 16 bit Voltage Output SoftSpan DAC driver
+ *
+ * Copyright 2022 Analog Devices Inc.
+ */
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/limits.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#define LTC2688_DAC_CHANNELS			16
+
+#define LTC2688_CMD_CH_CODE(x)			(0x00 + (x))
+#define LTC2688_CMD_CH_SETTING(x)		(0x10 + (x))
+#define LTC2688_CMD_CH_OFFSET(x)		(0X20 + (x))
+#define LTC2688_CMD_CH_GAIN(x)			(0x30 + (x))
+#define LTC2688_CMD_CH_CODE_UPDATE(x)		(0x40 + (x))
+
+#define LTC2688_CMD_CONFIG			0x70
+#define LTC2688_CMD_POWERDOWN			0x71
+#define LTC2688_CMD_A_B_SELECT			0x72
+#define LTC2688_CMD_SW_TOGGLE			0x73
+#define LTC2688_CMD_TOGGLE_DITHER_EN		0x74
+#define LTC2688_CMD_THERMAL_STAT		0x77
+#define LTC2688_CMD_UPDATE_ALL			0x7C
+#define LTC2688_CMD_NOOP			0xFF
+
+#define LTC2688_READ_OPERATION			0x80
+
+/* Channel Settings */
+#define LTC2688_CH_SPAN_MSK			GENMASK(2, 0)
+#define LTC2688_CH_OVERRANGE_MSK		BIT(3)
+#define LTC2688_CH_TD_SEL_MSK			GENMASK(5, 4)
+#define LTC2688_CH_TGP_MAX			3
+#define LTC2688_CH_DIT_PER_MSK			GENMASK(8, 6)
+#define LTC2688_CH_DIT_PH_MSK			GENMASK(10, 9)
+#define LTC2688_CH_MODE_MSK			BIT(11)
+
+#define LTC2688_DITHER_RAW_MASK			GENMASK(15, 2)
+#define LTC2688_CH_CALIBBIAS_MASK		GENMASK(15, 2)
+#define LTC2688_DITHER_RAW_MAX_VAL		(BIT(14) - 1)
+#define LTC2688_CH_CALIBBIAS_MAX_VAL		(BIT(14) - 1)
+
+/* Configuration register */
+#define LTC2688_CONFIG_RST			BIT(15)
+#define LTC2688_CONFIG_EXT_REF			BIT(1)
+
+#define LTC2688_DITHER_FREQ_AVAIL_N		5
+
+enum {
+	LTC2688_SPAN_RANGE_0V_5V,
+	LTC2688_SPAN_RANGE_0V_10V,
+	LTC2688_SPAN_RANGE_M5V_5V,
+	LTC2688_SPAN_RANGE_M10V_10V,
+	LTC2688_SPAN_RANGE_M15V_15V,
+	LTC2688_SPAN_RANGE_MAX
+};
+
+enum {
+	LTC2688_MODE_DEFAULT,
+	LTC2688_MODE_DITHER_TOGGLE,
+};
+
+struct ltc2688_chan {
+	long dither_frequency[LTC2688_DITHER_FREQ_AVAIL_N];
+	bool overrange;
+	bool toggle_chan;
+	u8 mode;
+};
+
+struct ltc2688_state {
+	struct spi_device *spi;
+	struct regmap *regmap;
+	struct regulator_bulk_data regulators[2];
+	struct ltc2688_chan channels[LTC2688_DAC_CHANNELS];
+	struct iio_chan_spec *iio_chan;
+	/* lock to protect against multiple access to the device and shared data */
+	struct mutex lock;
+	int vref;
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	u8 tx_data[6] ____cacheline_aligned;
+	u8 rx_data[3];
+};
+
+static int ltc2688_spi_read(void *context, const void *reg, size_t reg_size,
+			    void *val, size_t val_size)
+{
+	struct ltc2688_state *st = context;
+	struct spi_transfer xfers[] = {
+		{
+			.tx_buf = st->tx_data,
+			.bits_per_word = 8,
+			.len = reg_size + val_size,
+			.cs_change = 1,
+		}, {
+			.tx_buf = st->tx_data + 3,
+			.rx_buf = st->rx_data,
+			.bits_per_word = 8,
+			.len = reg_size + val_size,
+		},
+	};
+	int ret;
+
+	memcpy(st->tx_data, reg, reg_size);
+
+	ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
+	if (ret)
+		return ret;
+
+	memcpy(val, &st->rx_data[1], val_size);
+
+	return 0;
+}
+
+static int ltc2688_spi_write(void *context, const void *data, size_t count)
+{
+	struct ltc2688_state *st = context;
+
+	return spi_write(st->spi, data, count);
+}
+
+static int ltc2688_span_get(const struct ltc2688_state *st, int c)
+{
+	int ret, reg, span;
+
+	ret = regmap_read(st->regmap, LTC2688_CMD_CH_SETTING(c), &reg);
+	if (ret)
+		return ret;
+
+	span = FIELD_GET(LTC2688_CH_SPAN_MSK, reg);
+	/* sanity check to make sure we don't get any weird value from the HW */
+	if (span >= LTC2688_SPAN_RANGE_MAX)
+		return -EIO;
+
+	return span;
+}
+
+static const int ltc2688_span_helper[LTC2688_SPAN_RANGE_MAX][2] = {
+	{0, 5000}, {0, 10000}, {-5000, 5000}, {-10000, 10000}, {-15000, 15000},
+};
+
+static int ltc2688_scale_get(const struct ltc2688_state *st, int c, int *val)
+{
+	const struct ltc2688_chan *chan = &st->channels[c];
+	int span, fs;
+
+	span = ltc2688_span_get(st, c);
+	if (span < 0)
+		return span;
+
+	fs = ltc2688_span_helper[span][1] - ltc2688_span_helper[span][0];
+	if (chan->overrange)
+		fs = mult_frac(fs, 105, 100);
+
+	*val = DIV_ROUND_CLOSEST(fs * st->vref, 4096);
+
+	return 0;
+}
+
+static int ltc2688_offset_get(const struct ltc2688_state *st, int c, int *val)
+{
+	int span;
+
+	span = ltc2688_span_get(st, c);
+	if (span < 0)
+		return span;
+
+	if (ltc2688_span_helper[span][0] < 0)
+		*val = -32768;
+	else
+		*val = 0;
+
+	return 0;
+}
+
+enum {
+	LTC2688_INPUT_A,
+	LTC2688_INPUT_B,
+	LTC2688_INPUT_B_AVAIL,
+	LTC2688_DITHER_OFF,
+	LTC2688_DITHER_FREQ_AVAIL,
+};
+
+static int ltc2688_dac_code_write(struct ltc2688_state *st, u32 chan, u32 input,
+				  u16 code)
+{
+	struct ltc2688_chan *c = &st->channels[chan];
+	int ret, reg;
+
+	/* 2 LSBs set to 0 if writing dither amplitude */
+	if (!c->toggle_chan && input == LTC2688_INPUT_B) {
+		if (code > LTC2688_DITHER_RAW_MAX_VAL)
+			return -EINVAL;
+
+		code = FIELD_PREP(LTC2688_DITHER_RAW_MASK, code);
+	}
+
+	mutex_lock(&st->lock);
+	/* select the correct input register to read from */
+	ret = regmap_update_bits(st->regmap, LTC2688_CMD_A_B_SELECT, BIT(chan),
+				 input << chan);
+	if (ret)
+		goto out_unlock;
+
+	/*
+	 * If in dither/toggle mode the dac should be updated by an
+	 * external signal (or sw toggle) and not here.
+	 */
+	if (c->mode == LTC2688_MODE_DEFAULT)
+		reg = LTC2688_CMD_CH_CODE_UPDATE(chan);
+	else
+		reg = LTC2688_CMD_CH_CODE(chan);
+
+	ret = regmap_write(st->regmap, reg, code);
+out_unlock:
+	mutex_unlock(&st->lock);
+	return ret;
+}
+
+static int ltc2688_dac_code_read(struct ltc2688_state *st, u32 chan, u32 input,
+				 u32 *code)
+{
+	struct ltc2688_chan *c = &st->channels[chan];
+	int ret;
+
+	mutex_lock(&st->lock);
+	ret = regmap_update_bits(st->regmap, LTC2688_CMD_A_B_SELECT, BIT(chan),
+				 input << chan);
+	if (ret)
+		goto out_unlock;
+
+	ret = regmap_read(st->regmap, LTC2688_CMD_CH_CODE(chan), code);
+out_unlock:
+	mutex_unlock(&st->lock);
+
+	if (!c->toggle_chan && input == LTC2688_INPUT_B)
+		*code = FIELD_GET(LTC2688_DITHER_RAW_MASK, *code);
+
+	return ret;
+}
+
+static const int ltc2688_raw_range[] = {0, 1, U16_MAX};
+
+static int ltc2688_read_avail(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      const int **vals, int *type, int *length,
+			      long info)
+{
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		*vals = ltc2688_raw_range;
+		*type = IIO_VAL_INT;
+		return IIO_AVAIL_RANGE;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ltc2688_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan, int *val,
+			    int *val2, long info)
+{
+	struct ltc2688_state *st = iio_priv(indio_dev);
+	int ret;
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		ret = ltc2688_dac_code_read(st, chan->channel, LTC2688_INPUT_A,
+					    val);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_OFFSET:
+		ret = ltc2688_offset_get(st, chan->channel, val);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		ret = ltc2688_scale_get(st, chan->channel, val);
+		if (ret)
+			return ret;
+
+		*val = 16;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	case IIO_CHAN_INFO_CALIBBIAS:
+		ret = regmap_read(st->regmap,
+				  LTC2688_CMD_CH_OFFSET(chan->channel), val);
+		if (ret)
+			return ret;
+
+		*val = FIELD_GET(LTC2688_CH_CALIBBIAS_MASK, *val);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_CALIBSCALE:
+		ret = regmap_read(st->regmap,
+				  LTC2688_CMD_CH_GAIN(chan->channel), val);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ltc2688_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, int val,
+			     int val2, long info)
+{
+	struct ltc2688_state *st = iio_priv(indio_dev);
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		if (val > U16_MAX || val < 0)
+			return -EINVAL;
+
+		return ltc2688_dac_code_write(st, chan->channel,
+					      LTC2688_INPUT_A, val);
+	case IIO_CHAN_INFO_CALIBBIAS:
+		if (val > LTC2688_CH_CALIBBIAS_MAX_VAL)
+			return -EINVAL;
+
+		return regmap_write(st->regmap,
+				    LTC2688_CMD_CH_OFFSET(chan->channel),
+				    FIELD_PREP(LTC2688_CH_CALIBBIAS_MASK, val));
+	case IIO_CHAN_INFO_CALIBSCALE:
+		return regmap_write(st->regmap,
+				    LTC2688_CMD_CH_GAIN(chan->channel), val);
+	default:
+		return -EINVAL;
+	}
+}
+
+static ssize_t ltc2688_dither_toggle_set(struct iio_dev *indio_dev,
+					 uintptr_t private,
+					 const struct iio_chan_spec *chan,
+					 const char *buf, size_t len)
+{
+	struct ltc2688_state *st = iio_priv(indio_dev);
+	struct ltc2688_chan *c = &st->channels[chan->channel];
+	int ret;
+	bool en;
+
+	ret = kstrtobool(buf, &en);
+	if (ret)
+		return ret;
+
+	mutex_lock(&st->lock);
+	ret = regmap_update_bits(st->regmap, LTC2688_CMD_TOGGLE_DITHER_EN,
+				 BIT(chan->channel), en << chan->channel);
+	if (ret)
+		goto out_unlock;
+
+	c->mode = en ? LTC2688_MODE_DITHER_TOGGLE : LTC2688_MODE_DEFAULT;
+out_unlock:
+	mutex_unlock(&st->lock);
+
+	return ret ?: len;
+}
+
+static ssize_t ltc2688_reg_bool_get(struct iio_dev *indio_dev,
+				    uintptr_t private,
+				    const struct iio_chan_spec *chan,
+				    char *buf)
+{
+	const struct ltc2688_state *st = iio_priv(indio_dev);
+	int ret;
+	u32 val;
+
+	ret = regmap_read(st->regmap, private, &val);
+	if (ret)
+		return ret;
+
+	return sysfs_emit(buf, "%u\n", !!(val & BIT(chan->channel)));
+}
+
+static ssize_t ltc2688_reg_bool_set(struct iio_dev *indio_dev,
+				    uintptr_t private,
+				    const struct iio_chan_spec *chan,
+				    const char *buf, size_t len)
+{
+	const struct ltc2688_state *st = iio_priv(indio_dev);
+	int ret;
+	bool en;
+
+	ret = kstrtobool(buf, &en);
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(st->regmap, private, BIT(chan->channel),
+				 en << chan->channel);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t ltc2688_dither_freq_avail(const struct ltc2688_state *st,
+					 const struct ltc2688_chan *chan,
+					 char *buf)
+{
+	int sz = 0;
+	u32 f;
+
+	for (f = 0; f < ARRAY_SIZE(chan->dither_frequency); f++)
+		sz += sysfs_emit_at(buf, sz, "%ld ", chan->dither_frequency[f]);
+
+	buf[sz - 1] = '\n';
+
+	return sz;
+}
+
+static ssize_t ltc2688_dither_freq_get(struct iio_dev *indio_dev,
+				       uintptr_t private,
+				       const struct iio_chan_spec *chan,
+				       char *buf)
+{
+	const struct ltc2688_state *st = iio_priv(indio_dev);
+	const struct ltc2688_chan *c = &st->channels[chan->channel];
+	u32 reg, freq;
+	int ret;
+
+	if (private == LTC2688_DITHER_FREQ_AVAIL)
+		return ltc2688_dither_freq_avail(st, c, buf);
+
+	ret = regmap_read(st->regmap, LTC2688_CMD_CH_SETTING(chan->channel),
+			  &reg);
+	if (ret)
+		return ret;
+
+	freq = FIELD_GET(LTC2688_CH_DIT_PER_MSK, reg);
+	if (freq >= ARRAY_SIZE(c->dither_frequency))
+		return -EIO;
+
+	return sysfs_emit(buf, "%ld\n", c->dither_frequency[freq]);
+}
+
+static ssize_t ltc2688_dither_freq_set(struct iio_dev *indio_dev,
+				       uintptr_t private,
+				       const struct iio_chan_spec *chan,
+				       const char *buf, size_t len)
+{
+	const struct ltc2688_state *st = iio_priv(indio_dev);
+	const struct ltc2688_chan *c = &st->channels[chan->channel];
+	long val;
+	u32 freq;
+	int ret;
+
+	if (private == LTC2688_DITHER_FREQ_AVAIL)
+		return -EINVAL;
+
+	ret = kstrtol(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	for (freq = 0; freq < ARRAY_SIZE(c->dither_frequency); freq++) {
+		if (val == c->dither_frequency[freq])
+			break;
+	}
+
+	if (freq == ARRAY_SIZE(c->dither_frequency))
+		return -EINVAL;
+
+	ret = regmap_update_bits(st->regmap,
+				 LTC2688_CMD_CH_SETTING(chan->channel),
+				 LTC2688_CH_DIT_PER_MSK,
+				 FIELD_PREP(LTC2688_CH_DIT_PER_MSK, freq));
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t ltc2688_dac_input_read(struct iio_dev *indio_dev,
+				      uintptr_t private,
+				      const struct iio_chan_spec *chan,
+				      char *buf)
+{
+	struct ltc2688_state *st = iio_priv(indio_dev);
+	int ret;
+	u32 val;
+
+	if (private == LTC2688_INPUT_B_AVAIL)
+		return sysfs_emit(buf, "[%u %u %u]\n", ltc2688_raw_range[0],
+				  ltc2688_raw_range[1],
+				  ltc2688_raw_range[2] / 4);
+
+	if (private == LTC2688_DITHER_OFF)
+		return sysfs_emit(buf, "0\n");
+
+	ret = ltc2688_dac_code_read(st, chan->channel, private, &val);
+	if (ret)
+		return ret;
+
+	return sysfs_emit(buf, "%u\n", val);
+}
+
+static ssize_t ltc2688_dac_input_write(struct iio_dev *indio_dev,
+				       uintptr_t private,
+				       const struct iio_chan_spec *chan,
+				       const char *buf, size_t len)
+{
+	struct ltc2688_state *st = iio_priv(indio_dev);
+	int ret;
+	u16 val;
+
+	if (private == LTC2688_INPUT_B_AVAIL || private == LTC2688_DITHER_OFF)
+		return -EINVAL;
+
+	ret = kstrtou16(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	ret = ltc2688_dac_code_write(st, chan->channel, private, val);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static int ltc2688_get_dither_phase(struct iio_dev *dev,
+				    const struct iio_chan_spec *chan)
+{
+	struct ltc2688_state *st = iio_priv(dev);
+	int ret, regval;
+
+	ret = regmap_read(st->regmap, LTC2688_CMD_CH_SETTING(chan->channel),
+			  &regval);
+	if (ret)
+		return ret;
+
+	return FIELD_GET(LTC2688_CH_DIT_PH_MSK, regval);
+}
+
+static int ltc2688_set_dither_phase(struct iio_dev *dev,
+				    const struct iio_chan_spec *chan,
+				    unsigned int phase)
+{
+	struct ltc2688_state *st = iio_priv(dev);
+
+	return regmap_update_bits(st->regmap,
+				  LTC2688_CMD_CH_SETTING(chan->channel),
+				  LTC2688_CH_DIT_PH_MSK,
+				  FIELD_PREP(LTC2688_CH_DIT_PH_MSK, phase));
+}
+
+static int ltc2688_reg_access(struct iio_dev *indio_dev,
+			      unsigned int reg,
+			      unsigned int writeval,
+			      unsigned int *readval)
+{
+	struct ltc2688_state *st = iio_priv(indio_dev);
+
+	if (readval)
+		return regmap_read(st->regmap, reg, readval);
+
+	return regmap_write(st->regmap, reg, writeval);
+}
+
+static const char * const ltc2688_dither_phase[] = {
+	"0", "1.5708", "3.14159", "4.71239",
+};
+
+static const struct iio_enum ltc2688_dither_phase_enum = {
+	.items = ltc2688_dither_phase,
+	.num_items = ARRAY_SIZE(ltc2688_dither_phase),
+	.set = ltc2688_set_dither_phase,
+	.get = ltc2688_get_dither_phase,
+};
+
+#define LTC2688_CHAN_EXT_INFO(_name, _what, _shared, _read, _write) {	\
+	.name = _name,							\
+	.read = (_read),						\
+	.write = (_write),						\
+	.private = (_what),						\
+	.shared = (_shared),						\
+}
+
+/*
+ * For toggle mode we only expose the symbol attr (sw_toggle) in case a TGPx is
+ * not provided in dts.
+ */
+static const struct iio_chan_spec_ext_info ltc2688_toggle_sym_ext_info[] = {
+	LTC2688_CHAN_EXT_INFO("raw0", LTC2688_INPUT_A, IIO_SEPARATE,
+			      ltc2688_dac_input_read, ltc2688_dac_input_write),
+	LTC2688_CHAN_EXT_INFO("raw1", LTC2688_INPUT_B, IIO_SEPARATE,
+			      ltc2688_dac_input_read, ltc2688_dac_input_write),
+	LTC2688_CHAN_EXT_INFO("toggle_en", LTC2688_CMD_TOGGLE_DITHER_EN,
+			      IIO_SEPARATE, ltc2688_reg_bool_get,
+			      ltc2688_dither_toggle_set),
+	LTC2688_CHAN_EXT_INFO("powerdown", LTC2688_CMD_POWERDOWN, IIO_SEPARATE,
+			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
+	LTC2688_CHAN_EXT_INFO("symbol", LTC2688_CMD_SW_TOGGLE, IIO_SEPARATE,
+			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
+	{}
+};
+
+static const struct iio_chan_spec_ext_info ltc2688_toggle_ext_info[] = {
+	LTC2688_CHAN_EXT_INFO("raw0", LTC2688_INPUT_A, IIO_SEPARATE,
+			      ltc2688_dac_input_read, ltc2688_dac_input_write),
+	LTC2688_CHAN_EXT_INFO("raw1", LTC2688_INPUT_B, IIO_SEPARATE,
+			      ltc2688_dac_input_read, ltc2688_dac_input_write),
+	LTC2688_CHAN_EXT_INFO("toggle_en", LTC2688_CMD_TOGGLE_DITHER_EN,
+			      IIO_SEPARATE, ltc2688_reg_bool_get,
+			      ltc2688_dither_toggle_set),
+	LTC2688_CHAN_EXT_INFO("powerdown", LTC2688_CMD_POWERDOWN, IIO_SEPARATE,
+			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
+	{}
+};
+
+static struct iio_chan_spec_ext_info ltc2688_dither_ext_info[] = {
+	LTC2688_CHAN_EXT_INFO("dither_raw", LTC2688_INPUT_B, IIO_SEPARATE,
+			      ltc2688_dac_input_read, ltc2688_dac_input_write),
+	LTC2688_CHAN_EXT_INFO("dither_raw_available", LTC2688_INPUT_B_AVAIL,
+			      IIO_SEPARATE, ltc2688_dac_input_read,
+			      ltc2688_dac_input_write),
+	LTC2688_CHAN_EXT_INFO("dither_offset", LTC2688_DITHER_OFF, IIO_SEPARATE,
+			      ltc2688_dac_input_read, ltc2688_dac_input_write),
+	/*
+	 * Not IIO_ENUM because the available freq needs to be computed at
+	 * probe. We could still use it, but it didn't felt much right.
+	 */
+	LTC2688_CHAN_EXT_INFO("dither_frequency", 0, IIO_SEPARATE,
+			      ltc2688_dither_freq_get, ltc2688_dither_freq_set),
+	LTC2688_CHAN_EXT_INFO("dither_frequency_available",
+			      LTC2688_DITHER_FREQ_AVAIL, IIO_SEPARATE,
+			      ltc2688_dither_freq_get, ltc2688_dither_freq_set),
+	IIO_ENUM("dither_phase", IIO_SEPARATE, &ltc2688_dither_phase_enum),
+	IIO_ENUM_AVAILABLE("dither_phase", IIO_SEPARATE,
+			   &ltc2688_dither_phase_enum),
+	LTC2688_CHAN_EXT_INFO("dither_en", LTC2688_CMD_TOGGLE_DITHER_EN,
+			      IIO_SEPARATE, ltc2688_reg_bool_get,
+			      ltc2688_dither_toggle_set),
+	LTC2688_CHAN_EXT_INFO("powerdown", LTC2688_CMD_POWERDOWN, IIO_SEPARATE,
+			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
+	{}
+};
+
+static const struct iio_chan_spec_ext_info ltc2688_ext_info[] = {
+	LTC2688_CHAN_EXT_INFO("powerdown", LTC2688_CMD_POWERDOWN, IIO_SEPARATE,
+			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
+	{}
+};
+
+#define LTC2688_CHANNEL(_chan) {					\
+	.type = IIO_VOLTAGE,						\
+	.indexed = 1,							\
+	.output = 1,							\
+	.channel = (_chan),						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_CALIBSCALE) |		\
+		BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET) |	\
+		BIT(IIO_CHAN_INFO_CALIBBIAS) | BIT(IIO_CHAN_INFO_RAW),	\
+	.info_mask_separate_available = BIT(IIO_CHAN_INFO_RAW),		\
+	.ext_info = ltc2688_ext_info,					\
+}
+
+static const struct iio_chan_spec ltc2688_channels[] = {
+	LTC2688_CHANNEL(0),
+	LTC2688_CHANNEL(1),
+	LTC2688_CHANNEL(2),
+	LTC2688_CHANNEL(3),
+	LTC2688_CHANNEL(4),
+	LTC2688_CHANNEL(5),
+	LTC2688_CHANNEL(6),
+	LTC2688_CHANNEL(7),
+	LTC2688_CHANNEL(8),
+	LTC2688_CHANNEL(9),
+	LTC2688_CHANNEL(10),
+	LTC2688_CHANNEL(11),
+	LTC2688_CHANNEL(12),
+	LTC2688_CHANNEL(13),
+	LTC2688_CHANNEL(14),
+	LTC2688_CHANNEL(15),
+};
+
+static void ltc2688_clk_disable(void *clk)
+{
+	clk_disable_unprepare(clk);
+}
+
+static const int ltc2688_period[LTC2688_DITHER_FREQ_AVAIL_N] = {
+	4, 8, 16, 32, 64,
+};
+
+static int ltc2688_tgp_clk_setup(struct ltc2688_state *st,
+				 struct ltc2688_chan *chan,
+				 struct fwnode_handle *node, int tgp)
+{
+	unsigned long rate;
+	struct clk *clk;
+	int ret, f;
+
+	clk = devm_get_clk_from_child(&st->spi->dev, to_of_node(node), NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(&st->spi->dev, PTR_ERR(clk),
+				     "failed to get tgp clk.\n");
+
+	ret = clk_prepare_enable(clk);
+	if (ret)
+		return dev_err_probe(&st->spi->dev, ret,
+				     "failed to enable tgp clk.\n");
+
+	ret = devm_add_action_or_reset(&st->spi->dev, ltc2688_clk_disable, clk);
+	if (ret)
+		return ret;
+
+	if (chan->toggle_chan)
+		return 0;
+
+	/* calculate available dither frequencies */
+	rate = clk_get_rate(clk);
+	for (f = 0; f < ARRAY_SIZE(chan->dither_frequency); f++)
+		chan->dither_frequency[f] = DIV_ROUND_CLOSEST(rate, ltc2688_period[f]);
+
+	return 0;
+}
+
+static int ltc2688_span_lookup(const struct ltc2688_state *st, int min, int max)
+{
+	u32 span;
+
+	for (span = 0; span < ARRAY_SIZE(ltc2688_span_helper); span++) {
+		if (min == ltc2688_span_helper[span][0] &&
+		    max == ltc2688_span_helper[span][1])
+			return span;
+	}
+
+	return -EINVAL;
+}
+
+static int ltc2688_channel_config(struct ltc2688_state *st)
+{
+	struct device *dev = &st->spi->dev;
+	struct fwnode_handle *child;
+	u32 reg, clk_input, val, tmp[2];
+	int ret, span;
+
+	device_for_each_child_node(dev, child) {
+		struct ltc2688_chan *chan;
+
+		ret = fwnode_property_read_u32(child, "reg", &reg);
+		if (ret) {
+			fwnode_handle_put(child);
+			return dev_err_probe(dev, ret,
+					     "Failed to get reg property\n");
+		}
+
+		if (reg >= LTC2688_DAC_CHANNELS) {
+			fwnode_handle_put(child);
+			return dev_err_probe(dev, -EINVAL,
+					     "reg bigger than: %d\n",
+					     LTC2688_DAC_CHANNELS);
+		}
+
+		val = 0;
+		chan = &st->channels[reg];
+		if (fwnode_property_read_bool(child, "adi,toggle-mode")) {
+			chan->toggle_chan = true;
+			/* assume sw toggle ABI */
+			st->iio_chan[reg].ext_info = ltc2688_toggle_sym_ext_info;
+			/*
+			 * Clear IIO_CHAN_INFO_RAW bit as toggle channels expose
+			 * out_voltage_raw{0|1} files.
+			 */
+			__clear_bit(IIO_CHAN_INFO_RAW,
+				    &st->iio_chan[reg].info_mask_separate);
+		}
+
+		ret = fwnode_property_read_u32_array(child, "adi,output-range-microvolt",
+						     tmp, ARRAY_SIZE(tmp));
+		if (!ret) {
+			span = ltc2688_span_lookup(st, (int)tmp[0] / 1000,
+						   tmp[1] / 1000);
+			if (span < 0) {
+				fwnode_handle_put(child);
+				return dev_err_probe(dev, -EINVAL,
+						     "output range not valid:[%d %d]\n",
+						     tmp[0], tmp[1]);
+			}
+
+			val |= FIELD_PREP(LTC2688_CH_SPAN_MSK, span);
+		}
+
+		ret = fwnode_property_read_u32(child, "adi,toggle-dither-input",
+					       &clk_input);
+		if (!ret) {
+			if (clk_input >= LTC2688_CH_TGP_MAX) {
+				fwnode_handle_put(child);
+				return dev_err_probe(dev, -EINVAL,
+						     "toggle-dither-input inv value(%d)\n",
+						     clk_input);
+			}
+
+			ret = ltc2688_tgp_clk_setup(st, chan, child, clk_input);
+			if (ret) {
+				fwnode_handle_put(child);
+				return ret;
+			}
+
+			/*
+			 * 0 means software toggle which is the default mode.
+			 * Hence the +1.
+			 */
+			val |= FIELD_PREP(LTC2688_CH_TD_SEL_MSK, clk_input + 1);
+
+			/*
+			 * If a TGPx is given, we automatically assume a dither
+			 * capable channel (unless toggle is already enabled).
+			 * On top of this we just set here the dither bit in the
+			 * channel settings. It won't have any effect until the
+			 * global toggle/dither bit is enabled.
+			 */
+			if (!chan->toggle_chan) {
+				val |= FIELD_PREP(LTC2688_CH_MODE_MSK, 1);
+				st->iio_chan[reg].ext_info = ltc2688_dither_ext_info;
+			} else {
+				/* wait, no sw toggle after all */
+				st->iio_chan[reg].ext_info = ltc2688_toggle_ext_info;
+			}
+		}
+
+		if (fwnode_property_read_bool(child, "adi,overrange")) {
+			chan->overrange = true;
+			val |= LTC2688_CH_OVERRANGE_MSK;
+		}
+
+		if (!val)
+			continue;
+
+		ret = regmap_write(st->regmap, LTC2688_CMD_CH_SETTING(reg),
+				   val);
+		if (ret) {
+			fwnode_handle_put(child);
+			return dev_err_probe(dev, -EINVAL,
+					     "failed to set chan settings\n");
+		}
+	}
+
+	return 0;
+}
+
+static int ltc2688_setup(struct ltc2688_state *st, struct regulator *vref)
+{
+	struct gpio_desc *gpio;
+	int ret;
+
+	/*
+	 * If we have a reset pin, use that to reset the board, If not, use
+	 * the reset bit.
+	 */
+	gpio = devm_gpiod_get_optional(&st->spi->dev, "clr", GPIOD_OUT_HIGH);
+	if (IS_ERR(gpio))
+		return dev_err_probe(&st->spi->dev, PTR_ERR(gpio),
+				     "Failed to get reset gpio");
+	if (gpio) {
+		usleep_range(1000, 1200);
+		/* bring device out of reset */
+		gpiod_set_value_cansleep(gpio, 0);
+	} else {
+		ret = regmap_update_bits(st->regmap, LTC2688_CMD_CONFIG,
+					 LTC2688_CONFIG_RST,
+					 LTC2688_CONFIG_RST);
+		if (ret)
+			return ret;
+	}
+
+	usleep_range(10000, 12000);
+
+	/*
+	 * Duplicate the default channel configuration as it can change during
+	 * @ltc2688_channel_config()
+	 */
+	st->iio_chan = devm_kmemdup(&st->spi->dev, ltc2688_channels,
+				    sizeof(ltc2688_channels), GFP_KERNEL);
+	if (!st->iio_chan)
+		return -ENOMEM;
+
+	ret = ltc2688_channel_config(st);
+	if (ret)
+		return ret;
+
+	if (!vref)
+		return 0;
+
+	return regmap_set_bits(st->regmap, LTC2688_CMD_CONFIG,
+			       LTC2688_CONFIG_EXT_REF);
+}
+
+static void ltc2688_disable_regulators(void *data)
+{
+	struct ltc2688_state *st = data;
+
+	regulator_bulk_disable(ARRAY_SIZE(st->regulators), st->regulators);
+}
+
+static void ltc2688_disable_regulator(void *regulator)
+{
+	regulator_disable(regulator);
+}
+
+static bool ltc2688_reg_readable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case LTC2688_CMD_CH_CODE(0) ... LTC2688_CMD_CH_GAIN(15):
+		return true;
+	case LTC2688_CMD_CONFIG ... LTC2688_CMD_THERMAL_STAT:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool ltc2688_reg_writable(struct device *dev, unsigned int reg)
+{
+	/*
+	 * There's a jump from 0x76 to 0x78 in the write codes and the thermal
+	 * status code is 0x77 (which is read only) so that we need to check
+	 * that special condition.
+	 */
+	if (reg <= LTC2688_CMD_UPDATE_ALL && reg != LTC2688_CMD_THERMAL_STAT)
+		return true;
+
+	return false;
+}
+
+static struct regmap_bus ltc2688_regmap_bus = {
+	.read = ltc2688_spi_read,
+	.write = ltc2688_spi_write,
+	.read_flag_mask = LTC2688_READ_OPERATION,
+	.reg_format_endian_default = REGMAP_ENDIAN_BIG,
+	.val_format_endian_default = REGMAP_ENDIAN_BIG,
+};
+
+static const struct regmap_config ltc2688_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.readable_reg = ltc2688_reg_readable,
+	.writeable_reg = ltc2688_reg_writable,
+	/* ignoring the no op command */
+	.max_register = LTC2688_CMD_UPDATE_ALL,
+};
+
+static const struct iio_info ltc2688_info = {
+	.write_raw = ltc2688_write_raw,
+	.read_raw = ltc2688_read_raw,
+	.read_avail = ltc2688_read_avail,
+	.debugfs_reg_access = ltc2688_reg_access,
+};
+
+static int ltc2688_probe(struct spi_device *spi)
+{
+	struct ltc2688_state *st;
+	struct iio_dev *indio_dev;
+	struct regulator *vref_reg;
+	struct device *dev = &spi->dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->spi = spi;
+
+	/* Just write this once. No need to do it in every regmap read. */
+	st->tx_data[3] = LTC2688_CMD_NOOP;
+	mutex_init(&st->lock);
+
+	st->regmap = devm_regmap_init(dev, &ltc2688_regmap_bus, st,
+				      &ltc2688_regmap_config);
+	if (IS_ERR(st->regmap))
+		return dev_err_probe(dev, PTR_ERR(st->regmap),
+				     "Failed to init regmap");
+
+	st->regulators[0].supply = "vcc";
+	st->regulators[1].supply = "iovcc";
+	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(st->regulators),
+				      st->regulators);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to get regulators\n");
+
+	ret = regulator_bulk_enable(ARRAY_SIZE(st->regulators), st->regulators);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable regulators\n");
+
+	ret = devm_add_action_or_reset(dev, ltc2688_disable_regulators, st);
+	if (ret)
+		return ret;
+
+	vref_reg = devm_regulator_get_optional(dev, "vref");
+	if (IS_ERR(vref_reg)) {
+		if (PTR_ERR(vref_reg) != -ENODEV)
+			return dev_err_probe(dev, PTR_ERR(vref_reg),
+					     "Failed to get vref regulator");
+
+		vref_reg = NULL;
+		/* internal reference */
+		st->vref = 4096;
+	} else {
+		ret = regulator_enable(vref_reg);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "Failed to enable vref regulators\n");
+
+		ret = devm_add_action_or_reset(dev, ltc2688_disable_regulator,
+					       vref_reg);
+		if (ret)
+			return ret;
+
+		ret = regulator_get_voltage(vref_reg);
+		if (ret < 0)
+			return dev_err_probe(dev, ret, "Failed to get vref\n");
+
+		st->vref = ret / 1000;
+	}
+
+	ret = ltc2688_setup(st, vref_reg);
+	if (ret)
+		return ret;
+
+	indio_dev->name = "ltc2688";
+	indio_dev->info = &ltc2688_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = st->iio_chan;
+	indio_dev->num_channels = ARRAY_SIZE(ltc2688_channels);
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id ltc2688_of_id[] = {
+	{ .compatible = "adi,ltc2688" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, ltc2688_of_id);
+
+static const struct spi_device_id ltc2688_id[] = {
+	{ "ltc2688" },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, ltc2688_id);
+
+static struct spi_driver ltc2688_driver = {
+	.driver = {
+		.name = "ltc2688",
+		.of_match_table = ltc2688_of_id,
+	},
+	.probe = ltc2688_probe,
+	.id_table = ltc2688_id,
+};
+module_spi_driver(ltc2688_driver);
+
+MODULE_AUTHOR("Nuno Sá <nuno.sa@analog.com>");
+MODULE_DESCRIPTION("Analog Devices LTC2688 DAC");
+MODULE_LICENSE("GPL");