[v3,1/2] SPI: Add driver for Cadence SPI controller
diff mbox

Message ID 1397132030-2440-1-git-send-email-harinik@xilinx.com
State New, archived
Headers show

Commit Message

Harini Katakam April 10, 2014, 12:13 p.m. UTC
Add driver for Cadence SPI controller. This is used in Xilinx Zynq.

Signed-off-by: Harini Katakam <harinik@xilinx.com>
---

Here is the v3 series but I have one concern.
The recent change in spi-core to use wait_for_completion_timeout
uses a timeout value calculated as follows:
ms = xfer->len * 8 * 1000/xfer->speed_hz;
wait_for_completion_timeout(msecs_to_jiffies(ms));

Firstly, the timeout value obtained from this is a too low.
This timeout is typically used for an error conditions such as
hardware hang etc. and using a value >1*HZ would be better.
This driver used to use similar timeout and as I understand, other
drivers also use similar values.

Second, the xfer->speed_hz used here is not necessarily the
actual speed set. The IP allows a limited set of divisors and the
divisor is chosen in driver such that the actual speed is <= requested speed.
Due to this the timeout value set here, sometimes falls short of the
actual time required to complete transfer; this happens especially with
very low frequencies. The difference in time higher than 20msecs.
And for very small transfers, the timeout is set to 1 jiffy.
Also, this is not considering any interrupt latencies or if the system
is fully loaded.

This might be cutting it too close, can the timeout value in core be increased?

v3 changes:
- Remove setup function.
  Make clock CPOL/CPHA setup a separate funtion and call this from
  prepare_transfer_hardware before enabling.
- Remove clk_enable/disable in prepare/unprepare_tranfer_hardware.
  Clock enable/diable pairs will be retained as before only in
  probe/remove and suspend/resume.
  Use of runtime_pms for efficiency will be planned later.
- Remove /bits/ in bindings for num-cs, use temporary u32 variable in driver.
- Rename requested_bytes and remaining_bytes to tx_bytes/rx_bytes.
- Remove unused macros.
- Add is-decoded-cs property and add support in driver set_cs funtion.

v2 changes:
- Use xilinx compatible string too.
- Changes read register and write register functions to static inline.
- Removed unecessary dev_info and dev_dbg prints.
- Return IRQ_HANDLED only when interrupt is handled.
- Use a default num-cs value.
- Do init_hardware before requesting irq.
- Remove unecessary master_put()
- Set master->max_speed_hz
- Check for busy in cdns_setup().
  Retained this function with this check as opposed to removing.
  The reason for this is clock configuration needs to be done for
  the first time before enable is done in prepare_hardware;
  prepare_hardware however, doesn't receive spi_device structure.
- Implememnt transfer_one instead of transfer_one_message.
  Remove wait_for_completion as this is done by core.
- Implement set_cs.
- Clock enable/disable in prepare/unprepare respectively.
- In suspend, remove reset of hardware; simply call unprepare_hardware.
- In suspend/resume call master_suspend/resume respectively.
- Check for irq<=0 in probe.
- Remove MODULE_ALIAS.

---
 drivers/spi/Kconfig       |    7 +
 drivers/spi/Makefile      |    1 +
 drivers/spi/spi-cadence.c |  673 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 681 insertions(+)
 create mode 100644 drivers/spi/spi-cadence.c

Comments

Mark Brown April 10, 2014, 12:21 p.m. UTC | #1
On Thu, Apr 10, 2014 at 05:43:49PM +0530, Harini Katakam wrote:

> Firstly, the timeout value obtained from this is a too low.
> This timeout is typically used for an error conditions such as
> hardware hang etc. and using a value >1*HZ would be better.
> This driver used to use similar timeout and as I understand, other
> drivers also use similar values.

Send patches...
Harini Katakam April 10, 2014, 12:23 p.m. UTC | #2
Hi Mark,

On Thu, Apr 10, 2014 at 5:51 PM, Mark Brown <broonie@kernel.org> wrote:
> On Thu, Apr 10, 2014 at 05:43:49PM +0530, Harini Katakam wrote:
>
>> Firstly, the timeout value obtained from this is a too low.
>> This timeout is typically used for an error conditions such as
>> hardware hang etc. and using a value >1*HZ would be better.
>> This driver used to use similar timeout and as I understand, other
>> drivers also use similar values.
>
> Send patches...

Ok thanks, I will.

Regards,
Harini
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Mark Brown April 10, 2014, 10:48 p.m. UTC | #3
On Thu, Apr 10, 2014 at 05:43:49PM +0530, Harini Katakam wrote:
> Add driver for Cadence SPI controller. This is used in Xilinx Zynq.

This looks mostly good, the issues below are very small.

> +static int __maybe_unused cdns_spi_suspend(struct device *dev)
> +{
> +	struct platform_device *pdev = container_of(dev,
> +			struct platform_device, dev);
> +	struct spi_master *master = platform_get_drvdata(pdev);
> +	struct cdns_spi *xspi = spi_master_get_devdata(master);
> +
> +	spi_master_suspend(master);
> +
> +	clk_disable(xspi->ref_clk);
> +
> +	clk_disable(xspi->pclk);

You're only doing clk_disable() here, I would expect the clocks to also
be unprepared over suspend - there is no value in leaving them prepared
that I can see.  Just use clk_unprepare_disable().

It would also be good (though not essential) to implement runtime PM and
disable the clocks while there are no transfers in progress for a small
power saving.  The auto_runtime_pm feature in the core will do the
runtime PM calls for you.

Otherwise this looks good.
Harini Katakam April 11, 2014, 3:36 a.m. UTC | #4
Hi Mark,

On Fri, Apr 11, 2014 at 4:18 AM, Mark Brown <broonie@kernel.org> wrote:
> On Thu, Apr 10, 2014 at 05:43:49PM +0530, Harini Katakam wrote:
>> Add driver for Cadence SPI controller. This is used in Xilinx Zynq.
>
> This looks mostly good, the issues below are very small.
>
>> +static int __maybe_unused cdns_spi_suspend(struct device *dev)
>> +{
>> +     struct platform_device *pdev = container_of(dev,
>> +                     struct platform_device, dev);
>> +     struct spi_master *master = platform_get_drvdata(pdev);
>> +     struct cdns_spi *xspi = spi_master_get_devdata(master);
>> +
>> +     spi_master_suspend(master);
>> +
>> +     clk_disable(xspi->ref_clk);
>> +
>> +     clk_disable(xspi->pclk);
>
> You're only doing clk_disable() here, I would expect the clocks to also
> be unprepared over suspend - there is no value in leaving them prepared
> that I can see.  Just use clk_unprepare_disable().
>
> It would also be good (though not essential) to implement runtime PM and
> disable the clocks while there are no transfers in progress for a small
> power saving.  The auto_runtime_pm feature in the core will do the
> runtime PM calls for you.
>
> Otherwise this looks good.

Thanks. I'll make these changes and send a v4 next week.

Regards,
Harini
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Harini Katakam April 14, 2014, 9:11 a.m. UTC | #5
Hi Mark,

On Fri, Apr 11, 2014 at 9:06 AM, Harini Katakam
<harinikatakamlinux@gmail.com> wrote:
> Hi Mark,
>
> On Fri, Apr 11, 2014 at 4:18 AM, Mark Brown <broonie@kernel.org> wrote:
>> On Thu, Apr 10, 2014 at 05:43:49PM +0530, Harini Katakam wrote:
>>> Add driver for Cadence SPI controller. This is used in Xilinx Zynq.
>>
>> This looks mostly good, the issues below are very small.
>>
>>> +static int __maybe_unused cdns_spi_suspend(struct device *dev)
>>> +{
>>> +     struct platform_device *pdev = container_of(dev,
>>> +                     struct platform_device, dev);
>>> +     struct spi_master *master = platform_get_drvdata(pdev);
>>> +     struct cdns_spi *xspi = spi_master_get_devdata(master);
>>> +
>>> +     spi_master_suspend(master);
>>> +
>>> +     clk_disable(xspi->ref_clk);
>>> +
>>> +     clk_disable(xspi->pclk);
>>
>> You're only doing clk_disable() here, I would expect the clocks to also
>> be unprepared over suspend - there is no value in leaving them prepared
>> that I can see.  Just use clk_unprepare_disable().
>>
>> It would also be good (though not essential) to implement runtime PM and
>> disable the clocks while there are no transfers in progress for a small
>> power saving.  The auto_runtime_pm feature in the core will do the
>> runtime PM calls for you.
>>
>> Otherwise this looks good.
>
> Thanks. I'll make these changes and send a v4 next week.
>

This driver without runtime PM will suffice our current requirements.
Disabling the clocks will offer some small power savings as you pointed out and
I will revisit this at a later time as an enhancement.

I have addressed the other review comment and sent out a v4.

Regards,
Harini
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Patch
diff mbox

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index efe1960..b0f091b 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -148,6 +148,13 @@  config SPI_BUTTERFLY
 	  inexpensive battery powered microcontroller evaluation board.
 	  This same cable can be used to flash new firmware.
 
+config SPI_CADENCE
+	tristate "Cadence SPI controller"
+	depends on SPI_MASTER
+	help
+	  This selects the Cadence SPI controller master driver
+	  used by Xilinx Zynq.
+
 config SPI_CLPS711X
 	tristate "CLPS711X host SPI controller"
 	depends on ARCH_CLPS711X || COMPILE_TEST
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index bd79266..3e503d6 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -22,6 +22,7 @@  obj-$(CONFIG_SPI_BFIN_V3)               += spi-bfin-v3.o
 obj-$(CONFIG_SPI_BFIN_SPORT)		+= spi-bfin-sport.o
 obj-$(CONFIG_SPI_BITBANG)		+= spi-bitbang.o
 obj-$(CONFIG_SPI_BUTTERFLY)		+= spi-butterfly.o
+obj-$(CONFIG_SPI_CADENCE)		+= spi-cadence.o
 obj-$(CONFIG_SPI_CLPS711X)		+= spi-clps711x.o
 obj-$(CONFIG_SPI_COLDFIRE_QSPI)		+= spi-coldfire-qspi.o
 obj-$(CONFIG_SPI_DAVINCI)		+= spi-davinci.o
diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
new file mode 100644
index 0000000..9a8289e
--- /dev/null
+++ b/drivers/spi/spi-cadence.c
@@ -0,0 +1,673 @@ 
+/*
+ * Cadence SPI controller driver (master mode only)
+ *
+ * Copyright (C) 2008 - 2014 Xilinx, Inc.
+ *
+ * based on Blackfin On-Chip SPI Driver (spi_bfin5xx.c)
+ *
+ * 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; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/spi/spi.h>
+
+/* Name of this driver */
+#define CDNS_SPI_NAME		"cdns-spi"
+
+/* Register offset definitions */
+#define CDNS_SPI_CR_OFFSET	0x00 /* Configuration  Register, RW */
+#define CDNS_SPI_ISR_OFFSET	0x04 /* Interrupt Status Register, RO */
+#define CDNS_SPI_IER_OFFSET	0x08 /* Interrupt Enable Register, WO */
+#define CDNS_SPI_IDR_OFFSET	0x0c /* Interrupt Disable Register, WO */
+#define CDNS_SPI_IMR_OFFSET	0x10 /* Interrupt Enabled Mask Register, RO */
+#define CDNS_SPI_ER_OFFSET	0x14 /* Enable/Disable Register, RW */
+#define CDNS_SPI_DR_OFFSET	0x18 /* Delay Register, RW */
+#define CDNS_SPI_TXD_OFFSET	0x1C /* Data Transmit Register, WO */
+#define CDNS_SPI_RXD_OFFSET	0x20 /* Data Receive Register, RO */
+#define CDNS_SPI_SICR_OFFSET	0x24 /* Slave Idle Count Register, RW */
+#define CDNS_SPI_THLD_OFFSET	0x28 /* Transmit FIFO Watermark Register,RW */
+
+/*
+ * SPI Configuration Register bit Masks
+ *
+ * This register contains various control bits that affect the operation
+ * of the SPI controller
+ */
+#define CDNS_SPI_CR_MANSTRT_MASK	0x00010000 /* Manual TX Start */
+#define CDNS_SPI_CR_CPHA_MASK		0x00000004 /* Clock Phase Control */
+#define CDNS_SPI_CR_CPOL_MASK		0x00000002 /* Clock Polarity Control */
+#define CDNS_SPI_CR_SSCTRL_MASK		0x00003C00 /* Slave Select Mask */
+#define CDNS_SPI_CR_BAUD_DIV_MASK	0x00000038 /* Baud Rate Divisor Mask */
+#define CDNS_SPI_CR_MSTREN_MASK		0x00000001 /* Master Enable Mask */
+#define CDNS_SPI_CR_MANSTRTEN_MASK	0x00008000 /* Manual TX Enable Mask */
+#define CDNS_SPI_CR_SSFORCE_MASK	0x00004000 /* Manual SS Enable Mask */
+#define CDNS_SPI_CR_BAUD_DIV_4_MASK	0x00000008 /* Default Baud Div Mask */
+#define CDNS_SPI_CR_DEFAULT_MASK	(CDNS_SPI_CR_MSTREN_MASK | \
+					CDNS_SPI_CR_SSCTRL_MASK | \
+					CDNS_SPI_CR_SSFORCE_MASK | \
+					CDNS_SPI_CR_BAUD_DIV_4_MASK)
+
+/*
+ * SPI Configuration Register - Baud rate and slave select
+ *
+ * These are the values used in the calculation of baud rate divisor and
+ * setting the slave select.
+ */
+
+#define CDNS_SPI_BAUD_DIV_MAX		7 /* Baud rate divisor maximum */
+#define CDNS_SPI_BAUD_DIV_MIN		1 /* Baud rate divisor minimum */
+#define CDNS_SPI_BAUD_DIV_SHIFT		3 /* Baud rate divisor shift in CR */
+#define CDNS_SPI_SS_SHIFT		10 /* Slave Select field shift in CR */
+#define CDNS_SPI_SS0			0x1 /* Slave Select zero */
+
+/*
+ * SPI Interrupt Registers bit Masks
+ *
+ * All the four interrupt registers (Status/Mask/Enable/Disable) have the same
+ * bit definitions.
+ */
+#define CDNS_SPI_IXR_TXOW_MASK	0x00000004 /* SPI TX FIFO Overwater */
+#define CDNS_SPI_IXR_MODF_MASK	0x00000002 /* SPI Mode Fault */
+#define CDNS_SPI_IXR_RXNEMTY_MASK 0x00000010 /* SPI RX FIFO Not Empty */
+#define CDNS_SPI_IXR_DEFAULT_MASK	(CDNS_SPI_IXR_TXOW_MASK | \
+					CDNS_SPI_IXR_MODF_MASK)
+#define CDNS_SPI_IXR_TXFULL_MASK	0x00000008 /* SPI TX Full */
+#define CDNS_SPI_IXR_ALL_MASK	0x0000007F /* SPI all interrupts */
+
+/*
+ * SPI Enable Register bit Masks
+ *
+ * This register is used to enable or disable the SPI controller
+ */
+#define CDNS_SPI_ER_ENABLE_MASK	0x00000001 /* SPI Enable Bit Mask */
+#define CDNS_SPI_ER_DISABLE_MASK	0x0 /* SPI Disable Bit Mask */
+
+/* SPI FIFO depth in bytes */
+#define CDNS_SPI_FIFO_DEPTH	128
+
+/* Default number of chip select lines */
+#define CDNS_SPI_DEFAULT_NUM_CS		4
+
+/**
+ * struct cdns_spi - This definition defines spi driver instance
+ * @regs:		Virtual address of the SPI controller registers
+ * @ref_clk:		Pointer to the peripheral clock
+ * @pclk:		Pointer to the APB clock
+ * @speed_hz:		Current SPI bus clock speed in Hz
+ * @txbuf:		Pointer	to the TX buffer
+ * @rxbuf:		Pointer to the RX buffer
+ * @tx_bytes:		Number of bytes left to transfer
+ * @rx_bytes:		Number of bytes requested
+ * @dev_busy:		Device busy flag
+ * @is_decoded_cs:	Flag for decoder property set or not
+ */
+struct cdns_spi {
+	void __iomem *regs;
+	struct clk *ref_clk;
+	struct clk *pclk;
+	u32 speed_hz;
+	const u8 *txbuf;
+	u8 *rxbuf;
+	int tx_bytes;
+	int rx_bytes;
+	u8 dev_busy;
+	u32 is_decoded_cs;
+};
+
+/* Macros for the SPI controller read/write */
+static inline u32 cdns_spi_read(struct cdns_spi *xspi, u32 offset)
+{
+	return readl_relaxed(xspi->regs + offset);
+}
+
+static inline void cdns_spi_write(struct cdns_spi *xspi, u32 offset, u32 val)
+{
+	writel_relaxed(val, xspi->regs + offset);
+}
+
+/**
+ * cdns_spi_init_hw - Initialize the hardware and configure the SPI controller
+ * @xspi:	Pointer to the cdns_spi structure
+ *
+ * On reset the SPI controller is configured to be in master mode, baud rate
+ * divisor is set to 4, threshold value for TX FIFO not full interrupt is set
+ * to 1 and size of the word to be transferred as 8 bit.
+ * This function initializes the SPI controller to disable and clear all the
+ * interrupts, enable manual slave select and manual start, deselect all the
+ * chip select lines, and enable the SPI controller.
+ */
+static void cdns_spi_init_hw(struct cdns_spi *xspi)
+{
+	cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET,
+		       CDNS_SPI_ER_DISABLE_MASK);
+	cdns_spi_write(xspi, CDNS_SPI_IDR_OFFSET,
+		       CDNS_SPI_IXR_ALL_MASK);
+
+	/* Clear the RX FIFO */
+	while (cdns_spi_read(xspi, CDNS_SPI_ISR_OFFSET) &
+	       CDNS_SPI_IXR_RXNEMTY_MASK)
+		cdns_spi_read(xspi, CDNS_SPI_RXD_OFFSET);
+
+	cdns_spi_write(xspi, CDNS_SPI_ISR_OFFSET,
+		       CDNS_SPI_IXR_ALL_MASK);
+	cdns_spi_write(xspi, CDNS_SPI_CR_OFFSET,
+		       CDNS_SPI_CR_DEFAULT_MASK);
+	cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET,
+		       CDNS_SPI_ER_ENABLE_MASK);
+}
+
+/**
+ * cdns_spi_chipselect - Select or deselect the chip select line
+ * @spi:	Pointer to the spi_device structure
+ * @is_on:	Select(0) or deselect (1) the chip select line
+ */
+static void cdns_spi_chipselect(struct spi_device *spi, bool is_high)
+{
+	struct cdns_spi *xspi = spi_master_get_devdata(spi->master);
+	u32 ctrl_reg;
+
+	ctrl_reg = cdns_spi_read(xspi, CDNS_SPI_CR_OFFSET);
+
+	if (is_high) {
+		/* Deselect the slave */
+		ctrl_reg |= CDNS_SPI_CR_SSCTRL_MASK;
+	} else {
+		/* Select the slave */
+		ctrl_reg &= ~CDNS_SPI_CR_SSCTRL_MASK;
+		if (!(xspi->is_decoded_cs))
+			ctrl_reg |= ((~(CDNS_SPI_SS0 << spi->chip_select)) <<
+				     CDNS_SPI_SS_SHIFT) &
+				     CDNS_SPI_CR_SSCTRL_MASK;
+		else
+			ctrl_reg |= (spi->chip_select << CDNS_SPI_SS_SHIFT) &
+				     CDNS_SPI_CR_SSCTRL_MASK;
+	}
+
+	cdns_spi_write(xspi, CDNS_SPI_CR_OFFSET, ctrl_reg);
+}
+
+/**
+ * cdns_spi_config_clock_mode - Sets clock polarity and phase
+ * @spi:	Pointer to the spi_device structure
+ *
+ * Sets the requested clock polarity and phase.
+ */
+static void cdns_spi_config_clock_mode(struct spi_device *spi)
+{
+	struct cdns_spi *xspi = spi_master_get_devdata(spi->master);
+	u32 ctrl_reg;
+
+	ctrl_reg = cdns_spi_read(xspi, CDNS_SPI_CR_OFFSET);
+
+	/* Set the SPI clock phase and clock polarity */
+	ctrl_reg &= ~(CDNS_SPI_CR_CPHA_MASK | CDNS_SPI_CR_CPOL_MASK);
+	if (spi->mode & SPI_CPHA)
+		ctrl_reg |= CDNS_SPI_CR_CPHA_MASK;
+	if (spi->mode & SPI_CPOL)
+		ctrl_reg |= CDNS_SPI_CR_CPOL_MASK;
+
+	cdns_spi_write(xspi, CDNS_SPI_CR_OFFSET, ctrl_reg);
+}
+
+/**
+ * cdns_spi_config_clock_freq - Sets clock frequency
+ * @spi:	Pointer to the spi_device structure
+ * @transfer:	Pointer to the spi_transfer structure which provides
+ *		information about next transfer setup parameters
+ *
+ * Sets the requested clock frequency.
+ * Note: If the requested frequency is not an exact match with what can be
+ * obtained using the prescalar value the driver sets the clock frequency which
+ * is lower than the requested frequency (maximum lower) for the transfer. If
+ * the requested frequency is higher or lower than that is supported by the SPI
+ * controller the driver will set the highest or lowest frequency supported by
+ * controller.
+ */
+static void cdns_spi_config_clock_freq(struct spi_device *spi,
+				  struct spi_transfer *transfer)
+{
+	struct cdns_spi *xspi = spi_master_get_devdata(spi->master);
+	u32 ctrl_reg, baud_rate_val;
+	unsigned long frequency;
+
+	frequency = clk_get_rate(xspi->ref_clk);
+
+	ctrl_reg = cdns_spi_read(xspi, CDNS_SPI_CR_OFFSET);
+
+	/* Set the clock frequency */
+	if (xspi->speed_hz != transfer->speed_hz) {
+		/* first valid value is 1 */
+		baud_rate_val = CDNS_SPI_BAUD_DIV_MIN;
+		while ((baud_rate_val < CDNS_SPI_BAUD_DIV_MAX) &&
+		       (frequency / (2 << baud_rate_val)) > transfer->speed_hz)
+			baud_rate_val++;
+
+		ctrl_reg &= ~CDNS_SPI_CR_BAUD_DIV_MASK;
+		ctrl_reg |= baud_rate_val << CDNS_SPI_BAUD_DIV_SHIFT;
+
+		xspi->speed_hz = frequency / (2 << baud_rate_val);
+	}
+	cdns_spi_write(xspi, CDNS_SPI_CR_OFFSET, ctrl_reg);
+}
+
+/**
+ * cdns_spi_setup_transfer - Configure SPI controller for specified transfer
+ * @spi:	Pointer to the spi_device structure
+ * @transfer:	Pointer to the spi_transfer structure which provides
+ *		information about next transfer setup parameters
+ *
+ * Sets the operational mode of SPI controller for the next SPI transfer and
+ * sets the requested clock frequency.
+ *
+ * Return:	Always 0
+ */
+static int cdns_spi_setup_transfer(struct spi_device *spi,
+				   struct spi_transfer *transfer)
+{
+	struct cdns_spi *xspi = spi_master_get_devdata(spi->master);
+
+	cdns_spi_config_clock_freq(spi, transfer);
+
+	dev_dbg(&spi->dev, "%s, mode %d, %u bits/w, %u clock speed\n",
+		__func__, spi->mode, spi->bits_per_word,
+		xspi->speed_hz);
+
+	return 0;
+}
+
+/**
+ * cdns_spi_fill_tx_fifo - Fills the TX FIFO with as many bytes as possible
+ * @xspi:	Pointer to the cdns_spi structure
+ */
+static void cdns_spi_fill_tx_fifo(struct cdns_spi *xspi)
+{
+	unsigned long trans_cnt = 0;
+
+	while ((trans_cnt < CDNS_SPI_FIFO_DEPTH) &&
+	       (xspi->tx_bytes > 0)) {
+		if (xspi->txbuf)
+			cdns_spi_write(xspi, CDNS_SPI_TXD_OFFSET,
+				       *xspi->txbuf++);
+		else
+			cdns_spi_write(xspi, CDNS_SPI_TXD_OFFSET, 0);
+
+		xspi->tx_bytes--;
+		trans_cnt++;
+	}
+}
+
+/**
+ * cdns_spi_irq - Interrupt service routine of the SPI controller
+ * @irq:	IRQ number
+ * @dev_id:	Pointer to the xspi structure
+ *
+ * This function handles TX empty and Mode Fault interrupts only.
+ * On TX empty interrupt this function reads the received data from RX FIFO and
+ * fills the TX FIFO if there is any data remaining to be transferred.
+ * On Mode Fault interrupt this function indicates that transfer is completed,
+ * the SPI subsystem will identify the error as the remaining bytes to be
+ * transferred is non-zero.
+ *
+ * Return:	IRQ_HANDLED when handled; IRQ_NONE otherwise.
+ */
+static irqreturn_t cdns_spi_irq(int irq, void *dev_id)
+{
+	struct spi_master *master = dev_id;
+	struct cdns_spi *xspi = spi_master_get_devdata(master);
+	u32 intr_status, status;
+
+	status = IRQ_NONE;
+	intr_status = cdns_spi_read(xspi, CDNS_SPI_ISR_OFFSET);
+	cdns_spi_write(xspi, CDNS_SPI_ISR_OFFSET, intr_status);
+
+	if (intr_status & CDNS_SPI_IXR_MODF_MASK) {
+		/* Indicate that transfer is completed, the SPI subsystem will
+		 * identify the error as the remaining bytes to be
+		 * transferred is non-zero
+		 */
+		cdns_spi_write(xspi, CDNS_SPI_IDR_OFFSET,
+			       CDNS_SPI_IXR_DEFAULT_MASK);
+		spi_finalize_current_transfer(master);
+		status = IRQ_HANDLED;
+	} else if (intr_status & CDNS_SPI_IXR_TXOW_MASK) {
+		unsigned long trans_cnt;
+
+		trans_cnt = xspi->rx_bytes - xspi->tx_bytes;
+
+		/* Read out the data from the RX FIFO */
+		while (trans_cnt) {
+			u8 data;
+
+			data = cdns_spi_read(xspi, CDNS_SPI_RXD_OFFSET);
+			if (xspi->rxbuf)
+				*xspi->rxbuf++ = data;
+
+			xspi->rx_bytes--;
+			trans_cnt--;
+		}
+
+		if (xspi->tx_bytes) {
+			/* There is more data to send */
+			cdns_spi_fill_tx_fifo(xspi);
+		} else {
+			/* Transfer is completed */
+			cdns_spi_write(xspi, CDNS_SPI_IDR_OFFSET,
+				       CDNS_SPI_IXR_DEFAULT_MASK);
+			spi_finalize_current_transfer(master);
+		}
+		status = IRQ_HANDLED;
+	}
+
+	return status;
+}
+
+/**
+ * cdns_transfer_one - Initiates the SPI transfer
+ * @master:	Pointer to spi_master structure
+ * @spi:	Pointer to the spi_device structure
+ * @transfer:	Pointer to the spi_transfer structure which provides
+ *		information about next transfer parameters
+ *
+ * This function fills the TX FIFO, starts the SPI transfer and
+ * returns a positive transfer count so that core will wait for completion.
+ *
+ * Return:	Number of bytes transferred in the last transfer
+ */
+static int cdns_transfer_one(struct spi_master *master,
+			     struct spi_device *spi,
+			     struct spi_transfer *transfer)
+{
+	struct cdns_spi *xspi = spi_master_get_devdata(master);
+
+	xspi->txbuf = transfer->tx_buf;
+	xspi->rxbuf = transfer->rx_buf;
+	xspi->tx_bytes = transfer->len;
+	xspi->rx_bytes = transfer->len;
+
+	cdns_spi_setup_transfer(spi, transfer);
+
+	cdns_spi_fill_tx_fifo(xspi);
+
+	cdns_spi_write(xspi, CDNS_SPI_IER_OFFSET,
+		       CDNS_SPI_IXR_DEFAULT_MASK);
+	return transfer->len;
+}
+
+/**
+ * cdns_prepare_transfer_hardware - Prepares hardware for transfer.
+ * @master:	Pointer to the spi_master structure which provides
+ *		information about the controller.
+ *
+ * This function enables SPI master controller.
+ *
+ * Return:	0 always
+ */
+static int cdns_prepare_transfer_hardware(struct spi_master *master)
+{
+	struct cdns_spi *xspi = spi_master_get_devdata(master);
+
+	cdns_spi_config_clock_mode(master->cur_msg->spi);
+
+	cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET,
+		       CDNS_SPI_ER_ENABLE_MASK);
+
+	return 0;
+}
+
+/**
+ * cdns_unprepare_transfer_hardware - Relaxes hardware after transfer
+ * @master:	Pointer to the spi_master structure which provides
+ *		information about the controller.
+ *
+ * This function disables the SPI master controller.
+ *
+ * Return:	0 always
+ */
+static int cdns_unprepare_transfer_hardware(struct spi_master *master)
+{
+	struct cdns_spi *xspi = spi_master_get_devdata(master);
+
+	cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET,
+		       CDNS_SPI_ER_DISABLE_MASK);
+
+	return 0;
+}
+
+/**
+ * cdns_spi_probe - Probe method for the SPI driver
+ * @pdev:	Pointer to the platform_device structure
+ *
+ * This function initializes the driver data structures and the hardware.
+ *
+ * Return:	0 on success and error value on error
+ */
+static int cdns_spi_probe(struct platform_device *pdev)
+{
+	int ret = 0, irq;
+	struct spi_master *master;
+	struct cdns_spi *xspi;
+	struct resource *res;
+	u32 num_cs;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*xspi));
+	if (master == NULL)
+		return -ENOMEM;
+
+	xspi = spi_master_get_devdata(master);
+	master->dev.of_node = pdev->dev.of_node;
+	platform_set_drvdata(pdev, master);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	xspi->regs = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(xspi->regs)) {
+		ret = PTR_ERR(xspi->regs);
+		goto remove_master;
+	}
+
+	xspi->pclk = devm_clk_get(&pdev->dev, "pclk");
+	if (IS_ERR(xspi->pclk)) {
+		dev_err(&pdev->dev, "pclk clock not found.\n");
+		ret = PTR_ERR(xspi->pclk);
+		goto remove_master;
+	}
+
+	xspi->ref_clk = devm_clk_get(&pdev->dev, "ref_clk");
+	if (IS_ERR(xspi->ref_clk)) {
+		dev_err(&pdev->dev, "ref_clk clock not found.\n");
+		ret = PTR_ERR(xspi->ref_clk);
+		goto remove_master;
+	}
+
+	ret = clk_prepare_enable(xspi->pclk);
+	if (ret) {
+		dev_err(&pdev->dev, "Unable to enable APB clock.\n");
+		goto remove_master;
+	}
+
+	ret = clk_prepare_enable(xspi->ref_clk);
+	if (ret) {
+		dev_err(&pdev->dev, "Unable to enable device clock.\n");
+		goto clk_dis_apb;
+	}
+
+	/* SPI controller initializations */
+	cdns_spi_init_hw(xspi);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq <= 0) {
+		ret = -ENXIO;
+		dev_err(&pdev->dev, "irq number is invalid\n");
+		goto remove_master;
+	}
+
+	ret = devm_request_irq(&pdev->dev, irq, cdns_spi_irq,
+			       0, pdev->name, master);
+	if (ret != 0) {
+		ret = -ENXIO;
+		dev_err(&pdev->dev, "request_irq failed\n");
+		goto remove_master;
+	}
+
+	ret = of_property_read_u32(pdev->dev.of_node, "num-cs", &num_cs);
+
+	if (ret < 0)
+		master->num_chipselect = CDNS_SPI_DEFAULT_NUM_CS;
+	else
+		master->num_chipselect = num_cs;
+
+	ret = of_property_read_u32(pdev->dev.of_node, "is-decoded-cs",
+				   &xspi->is_decoded_cs);
+
+	if (ret < 0)
+		xspi->is_decoded_cs = 0;
+
+	master->prepare_transfer_hardware = cdns_prepare_transfer_hardware;
+	master->transfer_one = cdns_transfer_one;
+	master->unprepare_transfer_hardware = cdns_unprepare_transfer_hardware;
+	master->set_cs = cdns_spi_chipselect;
+	master->mode_bits = SPI_CPOL | SPI_CPHA;
+
+	/* Set to default valid value */
+	master->max_speed_hz = clk_get_rate(xspi->ref_clk) / 4;
+	xspi->speed_hz = master->max_speed_hz;
+
+	master->bits_per_word_mask = SPI_BPW_MASK(8);
+
+	ret = spi_register_master(master);
+	if (ret) {
+		dev_err(&pdev->dev, "spi_register_master failed\n");
+		goto clk_dis_all;
+	}
+
+	return ret;
+
+clk_dis_all:
+	clk_disable_unprepare(xspi->ref_clk);
+clk_dis_apb:
+	clk_disable_unprepare(xspi->pclk);
+remove_master:
+	spi_master_put(master);
+	return ret;
+}
+
+/**
+ * cdns_spi_remove - Remove method for the SPI driver
+ * @pdev:	Pointer to the platform_device structure
+ *
+ * This function is called if a device is physically removed from the system or
+ * if the driver module is being unloaded. It frees all resources allocated to
+ * the device.
+ *
+ * Return:	0 on success and error value on error
+ */
+static int cdns_spi_remove(struct platform_device *pdev)
+{
+	struct spi_master *master = platform_get_drvdata(pdev);
+	struct cdns_spi *xspi = spi_master_get_devdata(master);
+
+	cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET,
+		       CDNS_SPI_ER_DISABLE_MASK);
+
+	clk_disable_unprepare(xspi->ref_clk);
+	clk_disable_unprepare(xspi->pclk);
+
+	spi_unregister_master(master);
+
+	return 0;
+}
+
+/**
+ * cdns_spi_suspend - Suspend method for the SPI driver
+ * @dev:	Address of the platform_device structure
+ *
+ * This function disables the SPI controller and
+ * changes the driver state to "suspend"
+ *
+ * Return:	Always 0
+ */
+static int __maybe_unused cdns_spi_suspend(struct device *dev)
+{
+	struct platform_device *pdev = container_of(dev,
+			struct platform_device, dev);
+	struct spi_master *master = platform_get_drvdata(pdev);
+	struct cdns_spi *xspi = spi_master_get_devdata(master);
+
+	spi_master_suspend(master);
+
+	clk_disable(xspi->ref_clk);
+
+	clk_disable(xspi->pclk);
+
+	return 0;
+}
+
+/**
+ * cdns_spi_resume - Resume method for the SPI driver
+ * @dev:	Address of the platform_device structure
+ *
+ * This function changes the driver state to "ready"
+ *
+ * Return:	0 on success and error value on error
+ */
+static int __maybe_unused cdns_spi_resume(struct device *dev)
+{
+	struct platform_device *pdev = container_of(dev,
+			struct platform_device, dev);
+	struct spi_master *master = platform_get_drvdata(pdev);
+	struct cdns_spi *xspi = spi_master_get_devdata(master);
+	int ret = 0;
+
+	ret = clk_enable(xspi->pclk);
+	if (ret) {
+		dev_err(dev, "Cannot enable APB clock.\n");
+		return ret;
+	}
+
+	ret = clk_enable(xspi->ref_clk);
+	if (ret) {
+		dev_err(dev, "Cannot enable device clock.\n");
+		clk_disable(xspi->pclk);
+		return ret;
+	}
+	spi_master_resume(master);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(cdns_spi_dev_pm_ops, cdns_spi_suspend,
+			 cdns_spi_resume);
+
+static struct of_device_id cdns_spi_of_match[] = {
+	{ .compatible = "xlnx,zynq-spi-r1p6" },
+	{ .compatible = "cdns,spi-r1p6" },
+	{ /* end of table */ }
+};
+MODULE_DEVICE_TABLE(of, cdns_spi_of_match);
+
+/* cdns_spi_driver - This structure defines the SPI subsystem platform driver */
+static struct platform_driver cdns_spi_driver = {
+	.probe	= cdns_spi_probe,
+	.remove	= cdns_spi_remove,
+	.driver = {
+		.name = CDNS_SPI_NAME,
+		.owner = THIS_MODULE,
+		.of_match_table = cdns_spi_of_match,
+		.pm = &cdns_spi_dev_pm_ops,
+	},
+};
+
+module_platform_driver(cdns_spi_driver);
+
+MODULE_AUTHOR("Xilinx, Inc.");
+MODULE_DESCRIPTION("Cadence SPI driver");
+MODULE_LICENSE("GPL");