[v2,1/4] spi: Add new driver for STMicroelectronics' SPI Controller

Commit Message

Lee Jones Dec. 2, 2014, 3:40 p.m. UTC

This patch adds support for the SPI portion of ST's SSC device.

Signed-off-by: Lee Jones <[e-mail]>
---
 drivers/spi/Kconfig       |   7 +
 drivers/spi/Makefile      |   1 +
 drivers/spi/spi-st-ssc4.c | 509 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 517 insertions(+)
 create mode 100644 drivers/spi/spi-st-ssc4.c

Comments

Patrice CHOTARD Dec. 2, 2014, 4:16 p.m. UTC | #1

Hi Lee

Some minors remarks below

Thanks

On 12/02/2014 04:40 PM, Lee Jones wrote:
> This patch adds support for the SPI portion of ST's SSC device.
>
> Signed-off-by: Lee Jones <[e-mail]>
> ---
>   drivers/spi/Kconfig       |   7 +
>   drivers/spi/Makefile      |   1 +
>   drivers/spi/spi-st-ssc4.c | 509 ++++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 517 insertions(+)
>   create mode 100644 drivers/spi/spi-st-ssc4.c
>
> diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
> index 84e7c9e..bd0a10f 100644
> --- a/drivers/spi/Kconfig
> +++ b/drivers/spi/Kconfig
> @@ -488,6 +488,13 @@ config SPI_SIRF
>   	help
>   	  SPI driver for CSR SiRFprimaII SoCs
>   
> +config SPI_ST_SSC4
> +	tristate "STMicroelectronics SPI SSC-based driver"
> +	depends on ARCH_STI || COMPILE_TEST
> +	help
> +	  STMicroelectronics SoCs support for SPI. If you say yes to
> +	  this option, support will be included for the SSC driven SPI.
> +
>   config SPI_SUN4I
>   	tristate "Allwinner A10 SoCs SPI controller"
>   	depends on ARCH_SUNXI || COMPILE_TEST
> diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
> index 78f24ca..c38e28c 100644
> --- a/drivers/spi/Makefile
> +++ b/drivers/spi/Makefile
> @@ -74,6 +74,7 @@ obj-$(CONFIG_SPI_SH_HSPI)		+= spi-sh-hspi.o
>   obj-$(CONFIG_SPI_SH_MSIOF)		+= spi-sh-msiof.o
>   obj-$(CONFIG_SPI_SH_SCI)		+= spi-sh-sci.o
>   obj-$(CONFIG_SPI_SIRF)		+= spi-sirf.o
> +obj-$(CONFIG_SPI_ST_SSC4)		+= spi-st-ssc4.o
>   obj-$(CONFIG_SPI_SUN4I)			+= spi-sun4i.o
>   obj-$(CONFIG_SPI_SUN6I)			+= spi-sun6i.o
>   obj-$(CONFIG_SPI_TEGRA114)		+= spi-tegra114.o
> diff --git a/drivers/spi/spi-st-ssc4.c b/drivers/spi/spi-st-ssc4.c
> new file mode 100644
> index 0000000..566d86c
> --- /dev/null
> +++ b/drivers/spi/spi-st-ssc4.c
> @@ -0,0 +1,509 @@
> +/*
> + *  Copyright (c) 2008-2014 STMicroelectronics Limited
> + *
> + *  Author: Angus Clark <[e-mail]>
> + *          Patrice Chotard <[e-mail]>
> + *          Lee Jones <[e-mail]>
> + *
> + *  SPI master mode controller driver, used in STMicroelectronics devices.
> + *
> + *  May be copied or modified under the terms of the GNU General Public
> + *  License Version 2.0 only.  See linux/COPYING for more information.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/of_gpio.h>
> +#include <linux/of_irq.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/spi/spi.h>
> +#include <linux/spi/spi_bitbang.h>
> +
> +/* SSC registers */
> +#define SSC_BRG				0x000
> +#define SSC_TBUF			0x004
> +#define SSC_RBUF			0x008
> +#define SSC_CTL				0x00C
> +#define SSC_IEN				0x010
> +#define SSC_I2C				0x018
> +
> +/* SSC Control */
> +#define SSC_CTL_DATA_WIDTH_9		0x8
> +#define SSC_CTL_DATA_WIDTH_MSK		0xf
> +#define SSC_CTL_BM			0xf
> +#define SSC_CTL_HB			BIT(4)
> +#define SSC_CTL_PH			BIT(5)
> +#define SSC_CTL_PO			BIT(6)
> +#define SSC_CTL_SR			BIT(7)
> +#define SSC_CTL_MS			BIT(8)
> +#define SSC_CTL_EN			BIT(9)
> +#define SSC_CTL_LPB			BIT(10)
> +#define SSC_CTL_EN_TX_FIFO		BIT(11)
> +#define SSC_CTL_EN_RX_FIFO		BIT(12)
> +#define SSC_CTL_EN_CLST_RX		BIT(13)
> +
> +/* SSC Interrupt Enable */
> +#define SSC_IEN_TEEN			BIT(2)
> +
> +#define FIFO_SIZE			8
> +
> +struct spi_st {
> +	/* SSC SPI Controller */
> +	void __iomem		*base;
> +	struct clk		*clk;
> +	struct device		*dev;
> +
> +	/* SSC SPI current transaction */
> +	const u8		*tx_ptr;
> +	u8			*rx_ptr;
> +	u16			bytes_per_word;
> +	unsigned int		words_remaining;
> +	unsigned int		baud;
> +	struct completion	done;
> +};
> +
> +static int spi_st_clk_enable(struct spi_st *spi_st)
> +{
> +	/*
> +	 * Current platforms use one of the core clocks for SPI and I2C.
> +	 * If we attempt to disable the clock, the system will hang.
> +	 *
> +	 * TODO: Remove this when platform supports power domains.
> +	 */
> +	return 0;
> +
> +	return clk_prepare_enable(spi_st->clk);
> +}
> +
> +static void spi_st_clk_disable(struct spi_st *spi_st)
> +{
> +	/*
> +	 * Current platforms use one of the core clocks for SPI and I2C.
> +	 * If we attempt to disable the clock, the system will hang.
> +	 *
> +	 * TODO: Remove this when platform supports power domains.
> +	 */
> +	return;
> +
> +	clk_disable_unprepare(spi_st->clk);
> +}
> +
> +/* Load the TX FIFO */
> +static void ssc_write_tx_fifo(struct spi_st *spi_st)
> +{
> +	unsigned int count, i;
> +	uint32_t word = 0;
> +
> +	if (spi_st->words_remaining > FIFO_SIZE)
> +		count = FIFO_SIZE;
> +	else
> +		count = spi_st->words_remaining;
> +
> +	for (i = 0; i < count; i++) {
> +		if (spi_st->tx_ptr) {
> +			if (spi_st->bytes_per_word == 1) {
> +				word = *spi_st->tx_ptr++;
> +			} else {
> +				word = *spi_st->tx_ptr++;
> +				word = *spi_st->tx_ptr++ | (word << 8);
> +			}
> +		}
> +		writel_relaxed(word, spi_st->base + SSC_TBUF);
> +	}
> +}
> +
> +/* Read the RX FIFO */
> +static void ssc_read_rx_fifo(struct spi_st *spi_st)
> +{
> +	unsigned int count, i;
> +	uint32_t word = 0;
> +
> +	if (spi_st->words_remaining > FIFO_SIZE)
> +		count = FIFO_SIZE;
> +	else
> +		count = spi_st->words_remaining;
> +
> +	for (i = 0; i < count; i++) {
> +		word = readl_relaxed(spi_st->base + SSC_RBUF);
> +
> +		if (spi_st->rx_ptr) {
> +			if (spi_st->bytes_per_word == 1) {
> +				*spi_st->rx_ptr++ = (uint8_t)word;
> +			} else {
> +				*spi_st->rx_ptr++ = (word >> 8);
> +				*spi_st->rx_ptr++ = word & 0xff;
> +			}
> +		}
> +	}
> +	spi_st->words_remaining -= count;
> +}
> +
> +static int spi_st_transfer_one(struct spi_master *master,
> +			       struct spi_device *spi, struct spi_transfer *t)
> +{
> +	struct spi_st *spi_st = spi_master_get_devdata(master);
> +	uint32_t ctl = 0;
> +
> +	/* Setup transfer */
> +	spi_st->tx_ptr = t->tx_buf;
> +	spi_st->rx_ptr = t->rx_buf;
> +
> +	if (spi->bits_per_word > 8) {
> +		/*
> +		 * Anything greater than 8 bits-per-word requires 2
> +		 * bytes-per-word in the RX/TX buffers
> +		 */
> +		spi_st->bytes_per_word = 2;
> +		spi_st->words_remaining = t->len / 2;
> +
> +	} else if (spi->bits_per_word == 8 && !(t->len & 0x1)) {
> +		/*
> +		 * If transfer is even-length, and 8 bits-per-word, then
> +		 * implement as half-length 16 bits-per-word transfer
> +		 */
> +		spi_st->bytes_per_word = 2;
> +		spi_st->words_remaining = t->len/2;

add space around "/"

> +
> +		/* Set SSC_CTL to 16 bits-per-word */
> +		ctl = readl_relaxed(spi_st->base + SSC_CTL);
> +		writel_relaxed((ctl | 0xf), spi_st->base + SSC_CTL);
> +
> +		readl_relaxed(spi_st->base + SSC_RBUF);
> +
> +	} else {
> +		spi_st->bytes_per_word = 1;
> +		spi_st->words_remaining = t->len;
> +	}
> +
> +	reinit_completion(&spi_st->done);
> +
> +	/* Start transfer by writing to the TX FIFO */
> +	ssc_write_tx_fifo(spi_st);
> +	writel_relaxed(SSC_IEN_TEEN, spi_st->base + SSC_IEN);
> +
> +	/* Wait for transfer to complete */
> +	wait_for_completion(&spi_st->done);
> +
> +	/* Restore SSC_CTL if necessary */
> +	if (ctl)
> +		writel_relaxed(ctl, spi_st->base + SSC_CTL);
> +
> +	spi_finalize_current_transfer(spi->master);
> +
> +	return t->len;
> +}
> +
> +static void spi_st_cleanup(struct spi_device *spi)
> +{
> +	int cs = spi->cs_gpio;
> +
> +	if (gpio_is_valid(cs))
> +		devm_gpio_free(&spi->dev, cs);
> +}
> +
> +/* the spi->mode bits understood by this driver: */
> +#define MODEBITS  (SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_LOOP | SPI_CS_HIGH)
> +static int spi_st_setup(struct spi_device *spi)
> +{
> +	struct spi_st *spi_st = spi_master_get_devdata(spi->master);
> +	u32 spi_st_clk, sscbrg, var;
> +	u32 hz = spi->max_speed_hz;
> +	int cs = spi->cs_gpio;
> +	int ret;
> +
> +	if (spi->mode & ~MODEBITS) {
> +		dev_err(&spi->dev, "unsupported mode bits 0x%x\n",
> +			spi->mode & ~MODEBITS);
> +		return -EINVAL;
> +	}
> +
> +	if (!hz)  {
> +		dev_err(&spi->dev, "max_speed_hz unspecified\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!gpio_is_valid(cs)) {
> +		dev_err(&spi->dev, "%d is not a valid gpio\n", cs);
> +		return -EINVAL;
> +	}
> +
> +	if (devm_gpio_request(&spi->dev, cs, dev_name(&spi->dev))) {
> +		dev_err(&spi->dev, "could not request gpio:%d\n", cs);
> +		return -EINVAL;
> +	}
> +
> +	ret = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
> +	if (ret)
> +		return ret;
> +
> +	spi_st_clk = clk_get_rate(spi_st->clk);
> +
> +	/* Set SSC_BRF */
> +	sscbrg = spi_st_clk / (2 * hz);
> +	if (sscbrg < 0x07 || sscbrg > (0x1 << 16)) {

(0x1 << 16) can be replaced by BIT(16)



> +		dev_err(&spi->dev,
> +			"baudrate %d outside valid range %d\n", sscbrg, hz);
> +		return -EINVAL;
> +	}
> +
> +	spi_st->baud = spi_st_clk / (2 * sscbrg);
> +	if (sscbrg == (0x1 << 16)) /* 16-bit counter wraps */

ditto

> +		sscbrg = 0x0;
> +
> +	writel_relaxed(sscbrg, spi_st->base + SSC_BRG);
> +
> +	dev_dbg(&spi->dev,
> +		"setting baudrate:target= %u hz, actual= %u hz, sscbrg= %u\n",
> +		hz, spi_st->baud, sscbrg);
> +
> +	 /* Set SSC_CTL and enable SSC */
> +	 var = readl_relaxed(spi_st->base + SSC_CTL);
> +	 var |= SSC_CTL_MS;
> +
> +	 if (spi->mode & SPI_CPOL)
> +		var |= SSC_CTL_PO;
> +	 else
> +		var &= ~SSC_CTL_PO;
> +
> +	 if (spi->mode & SPI_CPHA)
> +		var |= SSC_CTL_PH;
> +	 else
> +		var &= ~SSC_CTL_PH;
> +
> +	 if ((spi->mode & SPI_LSB_FIRST) == 0)
> +		var |= SSC_CTL_HB;
> +	 else
> +		var &= ~SSC_CTL_HB;
> +
> +	 if (spi->mode & SPI_LOOP)
> +		var |= SSC_CTL_LPB;
> +	 else
> +		var &= ~SSC_CTL_LPB;
> +
> +	 var &= ~SSC_CTL_DATA_WIDTH_MSK;
> +	 var |= (spi->bits_per_word - 1);
> +
> +	 var |= SSC_CTL_EN_TX_FIFO | SSC_CTL_EN_RX_FIFO;
> +	 var |= SSC_CTL_EN;
> +
> +	 writel_relaxed(var, spi_st->base + SSC_CTL);
> +
> +	 /* Clear the status register */
> +	 readl_relaxed(spi_st->base + SSC_RBUF);
> +
> +	 return 0;
> +}
> +
> +/* Interrupt fired when TX shift register becomes empty */
> +static irqreturn_t spi_st_irq(int irq, void *dev_id)
> +{
> +	struct spi_st *spi_st = (struct spi_st *)dev_id;
> +
> +	/* Read RX FIFO */
> +	ssc_read_rx_fifo(spi_st);
> +
> +	/* Fill TX FIFO */
> +	if (spi_st->words_remaining) {
> +		ssc_write_tx_fifo(spi_st);
> +	} else {
> +		/* TX/RX complete */
> +		writel_relaxed(0x0, spi_st->base + SSC_IEN);
> +		/*
> +		 * read SSC_IEN to ensure that this bit is set
> +		 * before re-enabling interrupt
> +		 */
> +		readl(spi_st->base + SSC_IEN);
> +		complete(&spi_st->done);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int spi_st_probe(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct spi_master *master;
> +	struct resource *res;
> +	struct spi_st *spi_st;
> +	int irq, ret = 0;
> +	u32 var;
> +
> +	master = spi_alloc_master(&pdev->dev, sizeof(*spi_st));
> +	if (!master)
> +		return -ENOMEM;
> +
> +	master->dev.of_node		= np;
> +	master->mode_bits		= MODEBITS;
> +	master->setup			= spi_st_setup;
> +	master->cleanup			= spi_st_cleanup;
> +	master->transfer_one		= spi_st_transfer_one;
> +	master->bits_per_word_mask	= SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
> +	master->auto_runtime_pm		= true;
> +	master->bus_num			= pdev->id;
> +	spi_st				= spi_master_get_devdata(master);
> +
> +	spi_st->clk = devm_clk_get(&pdev->dev, "ssc");
> +	if (IS_ERR(spi_st->clk)) {
> +		dev_err(&pdev->dev, "Unable to request clock\n");
> +		return PTR_ERR(spi_st->clk);
> +	}
> +
> +	ret = spi_st_clk_enable(spi_st);
> +	if (ret)
> +		return ret;
> +
> +	init_completion(&spi_st->done);
> +
> +	/* Get resources */
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	spi_st->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(spi_st->base)) {
> +		ret = PTR_ERR(spi_st->base);
> +		goto clk_disable;
> +	}
> +
> +	/* Disable I2C and Reset SSC */
> +	writel_relaxed(0x0, spi_st->base + SSC_I2C);
> +	var = readw_relaxed(spi_st->base + SSC_CTL);
> +	var |= SSC_CTL_SR;
> +	writel_relaxed(var, spi_st->base + SSC_CTL);
> +
> +	udelay(1);
> +	var = readl_relaxed(spi_st->base + SSC_CTL);
> +	var &= ~SSC_CTL_SR;
> +	writel_relaxed(var, spi_st->base + SSC_CTL);
> +
> +	/* Set SSC into slave mode before reconfiguring PIO pins */
> +	var = readl_relaxed(spi_st->base + SSC_CTL);
> +	var &= ~SSC_CTL_MS;
> +	writel_relaxed(var, spi_st->base + SSC_CTL);
> +
> +	irq = irq_of_parse_and_map(np, 0);
> +	if (!irq) {
> +		dev_err(&pdev->dev, "IRQ missing or invalid\n");
> +		ret = -EINVAL;
> +		goto clk_disable;
> +	}
> +
> +	ret = devm_request_irq(&pdev->dev, irq, spi_st_irq, 0,
> +			       pdev->name, spi_st);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to request irq %d\n", irq);
> +		goto clk_disable;
> +	}
> +
> +	/* by default the device is on */
> +	pm_runtime_set_active(&pdev->dev);
> +	pm_runtime_enable(&pdev->dev);
> +
> +	platform_set_drvdata(pdev, master);
> +
> +	ret = devm_spi_register_master(&pdev->dev, master);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to register master\n");
> +		goto clk_disable;
> +	}
> +
> +	return 0;
> +
> +clk_disable:
> +	spi_st_clk_disable(spi_st);
> +
> +	return ret;
> +}
> +
> +static int spi_st_remove(struct platform_device *pdev)
> +{
> +	struct spi_master *master = platform_get_drvdata(pdev);
> +	struct spi_st *spi_st = spi_master_get_devdata(master);
> +
> +	spi_st_clk_disable(spi_st);
> +
> +	pinctrl_pm_select_sleep_state(&pdev->dev);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM
> +static int spi_st_runtime_suspend(struct device *dev)
> +{
> +	struct spi_master *master = dev_get_drvdata(dev);
> +	struct spi_st *spi_st = spi_master_get_devdata(master);
> +
> +	writel_relaxed(0, spi_st->base + SSC_IEN);
> +	pinctrl_pm_select_sleep_state(dev);
> +
> +	spi_st_clk_disable(spi_st);
> +
> +	return 0;
> +}
> +
> +static int spi_st_runtime_resume(struct device *dev)
> +{
> +	struct spi_master *master = dev_get_drvdata(dev);
> +	struct spi_st *spi_st = spi_master_get_devdata(master);
> +	int ret;
> +
> +	ret = spi_st_clk_enable(spi_st);
> +	pinctrl_pm_select_default_state(dev);
> +
> +	return ret;
> +}
> +#endif
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int spi_st_suspend(struct device *dev)
> +{
> +	struct spi_master *master = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = spi_master_suspend(master);
> +	if (ret)
> +		return ret;
> +
> +	return pm_runtime_force_suspend(dev);
> +}
> +
> +static int spi_st_resume(struct device *dev)
> +{
> +	struct spi_master *master = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = spi_master_resume(master);
> +	if (ret)
> +		return ret;
> +
> +	return pm_runtime_force_resume(dev);
> +}
> +#endif
> +
> +static const struct dev_pm_ops spi_st_pm = {
> +	SET_SYSTEM_SLEEP_PM_OPS(spi_st_suspend, spi_st_resume)
> +	SET_RUNTIME_PM_OPS(spi_st_runtime_suspend, spi_st_runtime_resume, NULL)
> +};
> +
> +static struct of_device_id stm_spi_match[] = {
> +	{ .compatible = "st,comms-ssc4-spi", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, stm_spi_match);
> +
> +static struct platform_driver spi_st_driver = {
> +	.driver = {
> +		.name = "spi-st",
> +		.pm = &spi_st_pm,
> +		.of_match_table = of_match_ptr(stm_spi_match),
> +	},
> +	.probe = spi_st_probe,
> +	.remove = spi_st_remove,
> +};
> +module_platform_driver(spi_st_driver);
> +
> +MODULE_AUTHOR("Patrice Chotard <[e-mail]>");
> +MODULE_DESCRIPTION("STM SSC SPI driver");
> +MODULE_LICENSE("GPL v2");

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Lee Jones Dec. 3, 2014, 9:17 a.m. UTC | #2

> Some minors remarks below

Thanks Patrice.  I will fix these up in v3.

Mark,

  Would you mind casting your eye over this submission prior to
the v3 please?

> On 12/02/2014 04:40 PM, Lee Jones wrote:
> >This patch adds support for the SPI portion of ST's SSC device.
> >
> >Signed-off-by: Lee Jones <[e-mail]>
> >---
> >  drivers/spi/Kconfig       |   7 +
> >  drivers/spi/Makefile      |   1 +
> >  drivers/spi/spi-st-ssc4.c | 509 ++++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 517 insertions(+)
> >  create mode 100644 drivers/spi/spi-st-ssc4.c
> >
> >diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
> >index 84e7c9e..bd0a10f 100644
> >--- a/drivers/spi/Kconfig
> >+++ b/drivers/spi/Kconfig
> >@@ -488,6 +488,13 @@ config SPI_SIRF
> >  	help
> >  	  SPI driver for CSR SiRFprimaII SoCs
> >+config SPI_ST_SSC4
> >+	tristate "STMicroelectronics SPI SSC-based driver"
> >+	depends on ARCH_STI || COMPILE_TEST
> >+	help
> >+	  STMicroelectronics SoCs support for SPI. If you say yes to
> >+	  this option, support will be included for the SSC driven SPI.
> >+
> >  config SPI_SUN4I
> >  	tristate "Allwinner A10 SoCs SPI controller"
> >  	depends on ARCH_SUNXI || COMPILE_TEST
> >diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
> >index 78f24ca..c38e28c 100644
> >--- a/drivers/spi/Makefile
> >+++ b/drivers/spi/Makefile
> >@@ -74,6 +74,7 @@ obj-$(CONFIG_SPI_SH_HSPI)		+= spi-sh-hspi.o
> >  obj-$(CONFIG_SPI_SH_MSIOF)		+= spi-sh-msiof.o
> >  obj-$(CONFIG_SPI_SH_SCI)		+= spi-sh-sci.o
> >  obj-$(CONFIG_SPI_SIRF)		+= spi-sirf.o
> >+obj-$(CONFIG_SPI_ST_SSC4)		+= spi-st-ssc4.o
> >  obj-$(CONFIG_SPI_SUN4I)			+= spi-sun4i.o
> >  obj-$(CONFIG_SPI_SUN6I)			+= spi-sun6i.o
> >  obj-$(CONFIG_SPI_TEGRA114)		+= spi-tegra114.o
> >diff --git a/drivers/spi/spi-st-ssc4.c b/drivers/spi/spi-st-ssc4.c
> >new file mode 100644
> >index 0000000..566d86c
> >--- /dev/null
> >+++ b/drivers/spi/spi-st-ssc4.c
> >@@ -0,0 +1,509 @@
> >+/*
> >+ *  Copyright (c) 2008-2014 STMicroelectronics Limited
> >+ *
> >+ *  Author: Angus Clark <[e-mail]>
> >+ *          Patrice Chotard <[e-mail]>
> >+ *          Lee Jones <[e-mail]>
> >+ *
> >+ *  SPI master mode controller driver, used in STMicroelectronics devices.
> >+ *
> >+ *  May be copied or modified under the terms of the GNU General Public
> >+ *  License Version 2.0 only.  See linux/COPYING for more information.
> >+ */
> >+
> >+#include <linux/clk.h>
> >+#include <linux/delay.h>
> >+#include <linux/interrupt.h>
> >+#include <linux/io.h>
> >+#include <linux/module.h>
> >+#include <linux/platform_device.h>
> >+#include <linux/of.h>
> >+#include <linux/of_gpio.h>
> >+#include <linux/of_irq.h>
> >+#include <linux/pm_runtime.h>
> >+#include <linux/spi/spi.h>
> >+#include <linux/spi/spi_bitbang.h>
> >+
> >+/* SSC registers */
> >+#define SSC_BRG				0x000
> >+#define SSC_TBUF			0x004
> >+#define SSC_RBUF			0x008
> >+#define SSC_CTL				0x00C
> >+#define SSC_IEN				0x010
> >+#define SSC_I2C				0x018
> >+
> >+/* SSC Control */
> >+#define SSC_CTL_DATA_WIDTH_9		0x8
> >+#define SSC_CTL_DATA_WIDTH_MSK		0xf
> >+#define SSC_CTL_BM			0xf
> >+#define SSC_CTL_HB			BIT(4)
> >+#define SSC_CTL_PH			BIT(5)
> >+#define SSC_CTL_PO			BIT(6)
> >+#define SSC_CTL_SR			BIT(7)
> >+#define SSC_CTL_MS			BIT(8)
> >+#define SSC_CTL_EN			BIT(9)
> >+#define SSC_CTL_LPB			BIT(10)
> >+#define SSC_CTL_EN_TX_FIFO		BIT(11)
> >+#define SSC_CTL_EN_RX_FIFO		BIT(12)
> >+#define SSC_CTL_EN_CLST_RX		BIT(13)
> >+
> >+/* SSC Interrupt Enable */
> >+#define SSC_IEN_TEEN			BIT(2)
> >+
> >+#define FIFO_SIZE			8
> >+
> >+struct spi_st {
> >+	/* SSC SPI Controller */
> >+	void __iomem		*base;
> >+	struct clk		*clk;
> >+	struct device		*dev;
> >+
> >+	/* SSC SPI current transaction */
> >+	const u8		*tx_ptr;
> >+	u8			*rx_ptr;
> >+	u16			bytes_per_word;
> >+	unsigned int		words_remaining;
> >+	unsigned int		baud;
> >+	struct completion	done;
> >+};
> >+
> >+static int spi_st_clk_enable(struct spi_st *spi_st)
> >+{
> >+	/*
> >+	 * Current platforms use one of the core clocks for SPI and I2C.
> >+	 * If we attempt to disable the clock, the system will hang.
> >+	 *
> >+	 * TODO: Remove this when platform supports power domains.
> >+	 */
> >+	return 0;
> >+
> >+	return clk_prepare_enable(spi_st->clk);
> >+}
> >+
> >+static void spi_st_clk_disable(struct spi_st *spi_st)
> >+{
> >+	/*
> >+	 * Current platforms use one of the core clocks for SPI and I2C.
> >+	 * If we attempt to disable the clock, the system will hang.
> >+	 *
> >+	 * TODO: Remove this when platform supports power domains.
> >+	 */
> >+	return;
> >+
> >+	clk_disable_unprepare(spi_st->clk);
> >+}
> >+
> >+/* Load the TX FIFO */
> >+static void ssc_write_tx_fifo(struct spi_st *spi_st)
> >+{
> >+	unsigned int count, i;
> >+	uint32_t word = 0;
> >+
> >+	if (spi_st->words_remaining > FIFO_SIZE)
> >+		count = FIFO_SIZE;
> >+	else
> >+		count = spi_st->words_remaining;
> >+
> >+	for (i = 0; i < count; i++) {
> >+		if (spi_st->tx_ptr) {
> >+			if (spi_st->bytes_per_word == 1) {
> >+				word = *spi_st->tx_ptr++;
> >+			} else {
> >+				word = *spi_st->tx_ptr++;
> >+				word = *spi_st->tx_ptr++ | (word << 8);
> >+			}
> >+		}
> >+		writel_relaxed(word, spi_st->base + SSC_TBUF);
> >+	}
> >+}
> >+
> >+/* Read the RX FIFO */
> >+static void ssc_read_rx_fifo(struct spi_st *spi_st)
> >+{
> >+	unsigned int count, i;
> >+	uint32_t word = 0;
> >+
> >+	if (spi_st->words_remaining > FIFO_SIZE)
> >+		count = FIFO_SIZE;
> >+	else
> >+		count = spi_st->words_remaining;
> >+
> >+	for (i = 0; i < count; i++) {
> >+		word = readl_relaxed(spi_st->base + SSC_RBUF);
> >+
> >+		if (spi_st->rx_ptr) {
> >+			if (spi_st->bytes_per_word == 1) {
> >+				*spi_st->rx_ptr++ = (uint8_t)word;
> >+			} else {
> >+				*spi_st->rx_ptr++ = (word >> 8);
> >+				*spi_st->rx_ptr++ = word & 0xff;
> >+			}
> >+		}
> >+	}
> >+	spi_st->words_remaining -= count;
> >+}
> >+
> >+static int spi_st_transfer_one(struct spi_master *master,
> >+			       struct spi_device *spi, struct spi_transfer *t)
> >+{
> >+	struct spi_st *spi_st = spi_master_get_devdata(master);
> >+	uint32_t ctl = 0;
> >+
> >+	/* Setup transfer */
> >+	spi_st->tx_ptr = t->tx_buf;
> >+	spi_st->rx_ptr = t->rx_buf;
> >+
> >+	if (spi->bits_per_word > 8) {
> >+		/*
> >+		 * Anything greater than 8 bits-per-word requires 2
> >+		 * bytes-per-word in the RX/TX buffers
> >+		 */
> >+		spi_st->bytes_per_word = 2;
> >+		spi_st->words_remaining = t->len / 2;
> >+
> >+	} else if (spi->bits_per_word == 8 && !(t->len & 0x1)) {
> >+		/*
> >+		 * If transfer is even-length, and 8 bits-per-word, then
> >+		 * implement as half-length 16 bits-per-word transfer
> >+		 */
> >+		spi_st->bytes_per_word = 2;
> >+		spi_st->words_remaining = t->len/2;
> 
> add space around "/"
> 
> >+
> >+		/* Set SSC_CTL to 16 bits-per-word */
> >+		ctl = readl_relaxed(spi_st->base + SSC_CTL);
> >+		writel_relaxed((ctl | 0xf), spi_st->base + SSC_CTL);
> >+
> >+		readl_relaxed(spi_st->base + SSC_RBUF);
> >+
> >+	} else {
> >+		spi_st->bytes_per_word = 1;
> >+		spi_st->words_remaining = t->len;
> >+	}
> >+
> >+	reinit_completion(&spi_st->done);
> >+
> >+	/* Start transfer by writing to the TX FIFO */
> >+	ssc_write_tx_fifo(spi_st);
> >+	writel_relaxed(SSC_IEN_TEEN, spi_st->base + SSC_IEN);
> >+
> >+	/* Wait for transfer to complete */
> >+	wait_for_completion(&spi_st->done);
> >+
> >+	/* Restore SSC_CTL if necessary */
> >+	if (ctl)
> >+		writel_relaxed(ctl, spi_st->base + SSC_CTL);
> >+
> >+	spi_finalize_current_transfer(spi->master);
> >+
> >+	return t->len;
> >+}
> >+
> >+static void spi_st_cleanup(struct spi_device *spi)
> >+{
> >+	int cs = spi->cs_gpio;
> >+
> >+	if (gpio_is_valid(cs))
> >+		devm_gpio_free(&spi->dev, cs);
> >+}
> >+
> >+/* the spi->mode bits understood by this driver: */
> >+#define MODEBITS  (SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_LOOP | SPI_CS_HIGH)
> >+static int spi_st_setup(struct spi_device *spi)
> >+{
> >+	struct spi_st *spi_st = spi_master_get_devdata(spi->master);
> >+	u32 spi_st_clk, sscbrg, var;
> >+	u32 hz = spi->max_speed_hz;
> >+	int cs = spi->cs_gpio;
> >+	int ret;
> >+
> >+	if (spi->mode & ~MODEBITS) {
> >+		dev_err(&spi->dev, "unsupported mode bits 0x%x\n",
> >+			spi->mode & ~MODEBITS);
> >+		return -EINVAL;
> >+	}
> >+
> >+	if (!hz)  {
> >+		dev_err(&spi->dev, "max_speed_hz unspecified\n");
> >+		return -EINVAL;
> >+	}
> >+
> >+	if (!gpio_is_valid(cs)) {
> >+		dev_err(&spi->dev, "%d is not a valid gpio\n", cs);
> >+		return -EINVAL;
> >+	}
> >+
> >+	if (devm_gpio_request(&spi->dev, cs, dev_name(&spi->dev))) {
> >+		dev_err(&spi->dev, "could not request gpio:%d\n", cs);
> >+		return -EINVAL;
> >+	}
> >+
> >+	ret = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
> >+	if (ret)
> >+		return ret;
> >+
> >+	spi_st_clk = clk_get_rate(spi_st->clk);
> >+
> >+	/* Set SSC_BRF */
> >+	sscbrg = spi_st_clk / (2 * hz);
> >+	if (sscbrg < 0x07 || sscbrg > (0x1 << 16)) {
> 
> (0x1 << 16) can be replaced by BIT(16)
> 
> 
> 
> >+		dev_err(&spi->dev,
> >+			"baudrate %d outside valid range %d\n", sscbrg, hz);
> >+		return -EINVAL;
> >+	}
> >+
> >+	spi_st->baud = spi_st_clk / (2 * sscbrg);
> >+	if (sscbrg == (0x1 << 16)) /* 16-bit counter wraps */
> 
> ditto
> 
> >+		sscbrg = 0x0;
> >+
> >+	writel_relaxed(sscbrg, spi_st->base + SSC_BRG);
> >+
> >+	dev_dbg(&spi->dev,
> >+		"setting baudrate:target= %u hz, actual= %u hz, sscbrg= %u\n",
> >+		hz, spi_st->baud, sscbrg);
> >+
> >+	 /* Set SSC_CTL and enable SSC */
> >+	 var = readl_relaxed(spi_st->base + SSC_CTL);
> >+	 var |= SSC_CTL_MS;
> >+
> >+	 if (spi->mode & SPI_CPOL)
> >+		var |= SSC_CTL_PO;
> >+	 else
> >+		var &= ~SSC_CTL_PO;
> >+
> >+	 if (spi->mode & SPI_CPHA)
> >+		var |= SSC_CTL_PH;
> >+	 else
> >+		var &= ~SSC_CTL_PH;
> >+
> >+	 if ((spi->mode & SPI_LSB_FIRST) == 0)
> >+		var |= SSC_CTL_HB;
> >+	 else
> >+		var &= ~SSC_CTL_HB;
> >+
> >+	 if (spi->mode & SPI_LOOP)
> >+		var |= SSC_CTL_LPB;
> >+	 else
> >+		var &= ~SSC_CTL_LPB;
> >+
> >+	 var &= ~SSC_CTL_DATA_WIDTH_MSK;
> >+	 var |= (spi->bits_per_word - 1);
> >+
> >+	 var |= SSC_CTL_EN_TX_FIFO | SSC_CTL_EN_RX_FIFO;
> >+	 var |= SSC_CTL_EN;
> >+
> >+	 writel_relaxed(var, spi_st->base + SSC_CTL);
> >+
> >+	 /* Clear the status register */
> >+	 readl_relaxed(spi_st->base + SSC_RBUF);
> >+
> >+	 return 0;
> >+}
> >+
> >+/* Interrupt fired when TX shift register becomes empty */
> >+static irqreturn_t spi_st_irq(int irq, void *dev_id)
> >+{
> >+	struct spi_st *spi_st = (struct spi_st *)dev_id;
> >+
> >+	/* Read RX FIFO */
> >+	ssc_read_rx_fifo(spi_st);
> >+
> >+	/* Fill TX FIFO */
> >+	if (spi_st->words_remaining) {
> >+		ssc_write_tx_fifo(spi_st);
> >+	} else {
> >+		/* TX/RX complete */
> >+		writel_relaxed(0x0, spi_st->base + SSC_IEN);
> >+		/*
> >+		 * read SSC_IEN to ensure that this bit is set
> >+		 * before re-enabling interrupt
> >+		 */
> >+		readl(spi_st->base + SSC_IEN);
> >+		complete(&spi_st->done);
> >+	}
> >+
> >+	return IRQ_HANDLED;
> >+}
> >+
> >+static int spi_st_probe(struct platform_device *pdev)
> >+{
> >+	struct device_node *np = pdev->dev.of_node;
> >+	struct spi_master *master;
> >+	struct resource *res;
> >+	struct spi_st *spi_st;
> >+	int irq, ret = 0;
> >+	u32 var;
> >+
> >+	master = spi_alloc_master(&pdev->dev, sizeof(*spi_st));
> >+	if (!master)
> >+		return -ENOMEM;
> >+
> >+	master->dev.of_node		= np;
> >+	master->mode_bits		= MODEBITS;
> >+	master->setup			= spi_st_setup;
> >+	master->cleanup			= spi_st_cleanup;
> >+	master->transfer_one		= spi_st_transfer_one;
> >+	master->bits_per_word_mask	= SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
> >+	master->auto_runtime_pm		= true;
> >+	master->bus_num			= pdev->id;
> >+	spi_st				= spi_master_get_devdata(master);
> >+
> >+	spi_st->clk = devm_clk_get(&pdev->dev, "ssc");
> >+	if (IS_ERR(spi_st->clk)) {
> >+		dev_err(&pdev->dev, "Unable to request clock\n");
> >+		return PTR_ERR(spi_st->clk);
> >+	}
> >+
> >+	ret = spi_st_clk_enable(spi_st);
> >+	if (ret)
> >+		return ret;
> >+
> >+	init_completion(&spi_st->done);
> >+
> >+	/* Get resources */
> >+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >+	spi_st->base = devm_ioremap_resource(&pdev->dev, res);
> >+	if (IS_ERR(spi_st->base)) {
> >+		ret = PTR_ERR(spi_st->base);
> >+		goto clk_disable;
> >+	}
> >+
> >+	/* Disable I2C and Reset SSC */
> >+	writel_relaxed(0x0, spi_st->base + SSC_I2C);
> >+	var = readw_relaxed(spi_st->base + SSC_CTL);
> >+	var |= SSC_CTL_SR;
> >+	writel_relaxed(var, spi_st->base + SSC_CTL);
> >+
> >+	udelay(1);
> >+	var = readl_relaxed(spi_st->base + SSC_CTL);
> >+	var &= ~SSC_CTL_SR;
> >+	writel_relaxed(var, spi_st->base + SSC_CTL);
> >+
> >+	/* Set SSC into slave mode before reconfiguring PIO pins */
> >+	var = readl_relaxed(spi_st->base + SSC_CTL);
> >+	var &= ~SSC_CTL_MS;
> >+	writel_relaxed(var, spi_st->base + SSC_CTL);
> >+
> >+	irq = irq_of_parse_and_map(np, 0);
> >+	if (!irq) {
> >+		dev_err(&pdev->dev, "IRQ missing or invalid\n");
> >+		ret = -EINVAL;
> >+		goto clk_disable;
> >+	}
> >+
> >+	ret = devm_request_irq(&pdev->dev, irq, spi_st_irq, 0,
> >+			       pdev->name, spi_st);
> >+	if (ret) {
> >+		dev_err(&pdev->dev, "Failed to request irq %d\n", irq);
> >+		goto clk_disable;
> >+	}
> >+
> >+	/* by default the device is on */
> >+	pm_runtime_set_active(&pdev->dev);
> >+	pm_runtime_enable(&pdev->dev);
> >+
> >+	platform_set_drvdata(pdev, master);
> >+
> >+	ret = devm_spi_register_master(&pdev->dev, master);
> >+	if (ret) {
> >+		dev_err(&pdev->dev, "Failed to register master\n");
> >+		goto clk_disable;
> >+	}
> >+
> >+	return 0;
> >+
> >+clk_disable:
> >+	spi_st_clk_disable(spi_st);
> >+
> >+	return ret;
> >+}
> >+
> >+static int spi_st_remove(struct platform_device *pdev)
> >+{
> >+	struct spi_master *master = platform_get_drvdata(pdev);
> >+	struct spi_st *spi_st = spi_master_get_devdata(master);
> >+
> >+	spi_st_clk_disable(spi_st);
> >+
> >+	pinctrl_pm_select_sleep_state(&pdev->dev);
> >+
> >+	return 0;
> >+}
> >+
> >+#ifdef CONFIG_PM
> >+static int spi_st_runtime_suspend(struct device *dev)
> >+{
> >+	struct spi_master *master = dev_get_drvdata(dev);
> >+	struct spi_st *spi_st = spi_master_get_devdata(master);
> >+
> >+	writel_relaxed(0, spi_st->base + SSC_IEN);
> >+	pinctrl_pm_select_sleep_state(dev);
> >+
> >+	spi_st_clk_disable(spi_st);
> >+
> >+	return 0;
> >+}
> >+
> >+static int spi_st_runtime_resume(struct device *dev)
> >+{
> >+	struct spi_master *master = dev_get_drvdata(dev);
> >+	struct spi_st *spi_st = spi_master_get_devdata(master);
> >+	int ret;
> >+
> >+	ret = spi_st_clk_enable(spi_st);
> >+	pinctrl_pm_select_default_state(dev);
> >+
> >+	return ret;
> >+}
> >+#endif
> >+
> >+#ifdef CONFIG_PM_SLEEP
> >+static int spi_st_suspend(struct device *dev)
> >+{
> >+	struct spi_master *master = dev_get_drvdata(dev);
> >+	int ret;
> >+
> >+	ret = spi_master_suspend(master);
> >+	if (ret)
> >+		return ret;
> >+
> >+	return pm_runtime_force_suspend(dev);
> >+}
> >+
> >+static int spi_st_resume(struct device *dev)
> >+{
> >+	struct spi_master *master = dev_get_drvdata(dev);
> >+	int ret;
> >+
> >+	ret = spi_master_resume(master);
> >+	if (ret)
> >+		return ret;
> >+
> >+	return pm_runtime_force_resume(dev);
> >+}
> >+#endif
> >+
> >+static const struct dev_pm_ops spi_st_pm = {
> >+	SET_SYSTEM_SLEEP_PM_OPS(spi_st_suspend, spi_st_resume)
> >+	SET_RUNTIME_PM_OPS(spi_st_runtime_suspend, spi_st_runtime_resume, NULL)
> >+};
> >+
> >+static struct of_device_id stm_spi_match[] = {
> >+	{ .compatible = "st,comms-ssc4-spi", },
> >+	{},
> >+};
> >+MODULE_DEVICE_TABLE(of, stm_spi_match);
> >+
> >+static struct platform_driver spi_st_driver = {
> >+	.driver = {
> >+		.name = "spi-st",
> >+		.pm = &spi_st_pm,
> >+		.of_match_table = of_match_ptr(stm_spi_match),
> >+	},
> >+	.probe = spi_st_probe,
> >+	.remove = spi_st_remove,
> >+};
> >+module_platform_driver(spi_st_driver);
> >+
> >+MODULE_AUTHOR("Patrice Chotard <[e-mail]>");
> >+MODULE_DESCRIPTION("STM SSC SPI driver");
> >+MODULE_LICENSE("GPL v2");
>

Mark Brown Dec. 4, 2014, 10:41 p.m. UTC | #3

On Wed, Dec 03, 2014 at 09:17:07AM +0000, Lee Jones wrote:

>   Would you mind casting your eye over this submission prior to
> the v3 please?

This all seems fine (which also means that the DT updates are good to
go).

Mark Brown Dec. 5, 2014, 5:19 p.m. UTC | #4

On Tue, Dec 02, 2014 at 03:40:41PM +0000, Lee Jones wrote:
> This patch adds support for the SPI portion of ST's SSC device.

Applied, thanks.

Patch

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 84e7c9e..bd0a10f 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -488,6 +488,13 @@  config SPI_SIRF
 	help
 	  SPI driver for CSR SiRFprimaII SoCs
 
+config SPI_ST_SSC4
+	tristate "STMicroelectronics SPI SSC-based driver"
+	depends on ARCH_STI || COMPILE_TEST
+	help
+	  STMicroelectronics SoCs support for SPI. If you say yes to
+	  this option, support will be included for the SSC driven SPI.
+
 config SPI_SUN4I
 	tristate "Allwinner A10 SoCs SPI controller"
 	depends on ARCH_SUNXI || COMPILE_TEST
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 78f24ca..c38e28c 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -74,6 +74,7 @@  obj-$(CONFIG_SPI_SH_HSPI)		+= spi-sh-hspi.o
 obj-$(CONFIG_SPI_SH_MSIOF)		+= spi-sh-msiof.o
 obj-$(CONFIG_SPI_SH_SCI)		+= spi-sh-sci.o
 obj-$(CONFIG_SPI_SIRF)		+= spi-sirf.o
+obj-$(CONFIG_SPI_ST_SSC4)		+= spi-st-ssc4.o
 obj-$(CONFIG_SPI_SUN4I)			+= spi-sun4i.o
 obj-$(CONFIG_SPI_SUN6I)			+= spi-sun6i.o
 obj-$(CONFIG_SPI_TEGRA114)		+= spi-tegra114.o
diff --git a/drivers/spi/spi-st-ssc4.c b/drivers/spi/spi-st-ssc4.c
new file mode 100644
index 0000000..566d86c
--- /dev/null
+++ b/drivers/spi/spi-st-ssc4.c
@@ -0,0 +1,509 @@ 
+/*
+ *  Copyright (c) 2008-2014 STMicroelectronics Limited
+ *
+ *  Author: Angus Clark <[e-mail]>
+ *          Patrice Chotard <[e-mail]>
+ *          Lee Jones <[e-mail]>
+ *
+ *  SPI master mode controller driver, used in STMicroelectronics devices.
+ *
+ *  May be copied or modified under the terms of the GNU General Public
+ *  License Version 2.0 only.  See linux/COPYING for more information.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>
+#include <linux/of_irq.h>
+#include <linux/pm_runtime.h>
+#include <linux/spi/spi.h>
+#include <linux/spi/spi_bitbang.h>
+
+/* SSC registers */
+#define SSC_BRG				0x000
+#define SSC_TBUF			0x004
+#define SSC_RBUF			0x008
+#define SSC_CTL				0x00C
+#define SSC_IEN				0x010
+#define SSC_I2C				0x018
+
+/* SSC Control */
+#define SSC_CTL_DATA_WIDTH_9		0x8
+#define SSC_CTL_DATA_WIDTH_MSK		0xf
+#define SSC_CTL_BM			0xf
+#define SSC_CTL_HB			BIT(4)
+#define SSC_CTL_PH			BIT(5)
+#define SSC_CTL_PO			BIT(6)
+#define SSC_CTL_SR			BIT(7)
+#define SSC_CTL_MS			BIT(8)
+#define SSC_CTL_EN			BIT(9)
+#define SSC_CTL_LPB			BIT(10)
+#define SSC_CTL_EN_TX_FIFO		BIT(11)
+#define SSC_CTL_EN_RX_FIFO		BIT(12)
+#define SSC_CTL_EN_CLST_RX		BIT(13)
+
+/* SSC Interrupt Enable */
+#define SSC_IEN_TEEN			BIT(2)
+
+#define FIFO_SIZE			8
+
+struct spi_st {
+	/* SSC SPI Controller */
+	void __iomem		*base;
+	struct clk		*clk;
+	struct device		*dev;
+
+	/* SSC SPI current transaction */
+	const u8		*tx_ptr;
+	u8			*rx_ptr;
+	u16			bytes_per_word;
+	unsigned int		words_remaining;
+	unsigned int		baud;
+	struct completion	done;
+};
+
+static int spi_st_clk_enable(struct spi_st *spi_st)
+{
+	/*
+	 * Current platforms use one of the core clocks for SPI and I2C.
+	 * If we attempt to disable the clock, the system will hang.
+	 *
+	 * TODO: Remove this when platform supports power domains.
+	 */
+	return 0;
+
+	return clk_prepare_enable(spi_st->clk);
+}
+
+static void spi_st_clk_disable(struct spi_st *spi_st)
+{
+	/*
+	 * Current platforms use one of the core clocks for SPI and I2C.
+	 * If we attempt to disable the clock, the system will hang.
+	 *
+	 * TODO: Remove this when platform supports power domains.
+	 */
+	return;
+
+	clk_disable_unprepare(spi_st->clk);
+}
+
+/* Load the TX FIFO */
+static void ssc_write_tx_fifo(struct spi_st *spi_st)
+{
+	unsigned int count, i;
+	uint32_t word = 0;
+
+	if (spi_st->words_remaining > FIFO_SIZE)
+		count = FIFO_SIZE;
+	else
+		count = spi_st->words_remaining;
+
+	for (i = 0; i < count; i++) {
+		if (spi_st->tx_ptr) {
+			if (spi_st->bytes_per_word == 1) {
+				word = *spi_st->tx_ptr++;
+			} else {
+				word = *spi_st->tx_ptr++;
+				word = *spi_st->tx_ptr++ | (word << 8);
+			}
+		}
+		writel_relaxed(word, spi_st->base + SSC_TBUF);
+	}
+}
+
+/* Read the RX FIFO */
+static void ssc_read_rx_fifo(struct spi_st *spi_st)
+{
+	unsigned int count, i;
+	uint32_t word = 0;
+
+	if (spi_st->words_remaining > FIFO_SIZE)
+		count = FIFO_SIZE;
+	else
+		count = spi_st->words_remaining;
+
+	for (i = 0; i < count; i++) {
+		word = readl_relaxed(spi_st->base + SSC_RBUF);
+
+		if (spi_st->rx_ptr) {
+			if (spi_st->bytes_per_word == 1) {
+				*spi_st->rx_ptr++ = (uint8_t)word;
+			} else {
+				*spi_st->rx_ptr++ = (word >> 8);
+				*spi_st->rx_ptr++ = word & 0xff;
+			}
+		}
+	}
+	spi_st->words_remaining -= count;
+}
+
+static int spi_st_transfer_one(struct spi_master *master,
+			       struct spi_device *spi, struct spi_transfer *t)
+{
+	struct spi_st *spi_st = spi_master_get_devdata(master);
+	uint32_t ctl = 0;
+
+	/* Setup transfer */
+	spi_st->tx_ptr = t->tx_buf;
+	spi_st->rx_ptr = t->rx_buf;
+
+	if (spi->bits_per_word > 8) {
+		/*
+		 * Anything greater than 8 bits-per-word requires 2
+		 * bytes-per-word in the RX/TX buffers
+		 */
+		spi_st->bytes_per_word = 2;
+		spi_st->words_remaining = t->len / 2;
+
+	} else if (spi->bits_per_word == 8 && !(t->len & 0x1)) {
+		/*
+		 * If transfer is even-length, and 8 bits-per-word, then
+		 * implement as half-length 16 bits-per-word transfer
+		 */
+		spi_st->bytes_per_word = 2;
+		spi_st->words_remaining = t->len/2;
+
+		/* Set SSC_CTL to 16 bits-per-word */
+		ctl = readl_relaxed(spi_st->base + SSC_CTL);
+		writel_relaxed((ctl | 0xf), spi_st->base + SSC_CTL);
+
+		readl_relaxed(spi_st->base + SSC_RBUF);
+
+	} else {
+		spi_st->bytes_per_word = 1;
+		spi_st->words_remaining = t->len;
+	}
+
+	reinit_completion(&spi_st->done);
+
+	/* Start transfer by writing to the TX FIFO */
+	ssc_write_tx_fifo(spi_st);
+	writel_relaxed(SSC_IEN_TEEN, spi_st->base + SSC_IEN);
+
+	/* Wait for transfer to complete */
+	wait_for_completion(&spi_st->done);
+
+	/* Restore SSC_CTL if necessary */
+	if (ctl)
+		writel_relaxed(ctl, spi_st->base + SSC_CTL);
+
+	spi_finalize_current_transfer(spi->master);
+
+	return t->len;
+}
+
+static void spi_st_cleanup(struct spi_device *spi)
+{
+	int cs = spi->cs_gpio;
+
+	if (gpio_is_valid(cs))
+		devm_gpio_free(&spi->dev, cs);
+}
+
+/* the spi->mode bits understood by this driver: */
+#define MODEBITS  (SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_LOOP | SPI_CS_HIGH)
+static int spi_st_setup(struct spi_device *spi)
+{
+	struct spi_st *spi_st = spi_master_get_devdata(spi->master);
+	u32 spi_st_clk, sscbrg, var;
+	u32 hz = spi->max_speed_hz;
+	int cs = spi->cs_gpio;
+	int ret;
+
+	if (spi->mode & ~MODEBITS) {
+		dev_err(&spi->dev, "unsupported mode bits 0x%x\n",
+			spi->mode & ~MODEBITS);
+		return -EINVAL;
+	}
+
+	if (!hz)  {
+		dev_err(&spi->dev, "max_speed_hz unspecified\n");
+		return -EINVAL;
+	}
+
+	if (!gpio_is_valid(cs)) {
+		dev_err(&spi->dev, "%d is not a valid gpio\n", cs);
+		return -EINVAL;
+	}
+
+	if (devm_gpio_request(&spi->dev, cs, dev_name(&spi->dev))) {
+		dev_err(&spi->dev, "could not request gpio:%d\n", cs);
+		return -EINVAL;
+	}
+
+	ret = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
+	if (ret)
+		return ret;
+
+	spi_st_clk = clk_get_rate(spi_st->clk);
+
+	/* Set SSC_BRF */
+	sscbrg = spi_st_clk / (2 * hz);
+	if (sscbrg < 0x07 || sscbrg > (0x1 << 16)) {
+		dev_err(&spi->dev,
+			"baudrate %d outside valid range %d\n", sscbrg, hz);
+		return -EINVAL;
+	}
+
+	spi_st->baud = spi_st_clk / (2 * sscbrg);
+	if (sscbrg == (0x1 << 16)) /* 16-bit counter wraps */
+		sscbrg = 0x0;
+
+	writel_relaxed(sscbrg, spi_st->base + SSC_BRG);
+
+	dev_dbg(&spi->dev,
+		"setting baudrate:target= %u hz, actual= %u hz, sscbrg= %u\n",
+		hz, spi_st->baud, sscbrg);
+
+	 /* Set SSC_CTL and enable SSC */
+	 var = readl_relaxed(spi_st->base + SSC_CTL);
+	 var |= SSC_CTL_MS;
+
+	 if (spi->mode & SPI_CPOL)
+		var |= SSC_CTL_PO;
+	 else
+		var &= ~SSC_CTL_PO;
+
+	 if (spi->mode & SPI_CPHA)
+		var |= SSC_CTL_PH;
+	 else
+		var &= ~SSC_CTL_PH;
+
+	 if ((spi->mode & SPI_LSB_FIRST) == 0)
+		var |= SSC_CTL_HB;
+	 else
+		var &= ~SSC_CTL_HB;
+
+	 if (spi->mode & SPI_LOOP)
+		var |= SSC_CTL_LPB;
+	 else
+		var &= ~SSC_CTL_LPB;
+
+	 var &= ~SSC_CTL_DATA_WIDTH_MSK;
+	 var |= (spi->bits_per_word - 1);
+
+	 var |= SSC_CTL_EN_TX_FIFO | SSC_CTL_EN_RX_FIFO;
+	 var |= SSC_CTL_EN;
+
+	 writel_relaxed(var, spi_st->base + SSC_CTL);
+
+	 /* Clear the status register */
+	 readl_relaxed(spi_st->base + SSC_RBUF);
+
+	 return 0;
+}
+
+/* Interrupt fired when TX shift register becomes empty */
+static irqreturn_t spi_st_irq(int irq, void *dev_id)
+{
+	struct spi_st *spi_st = (struct spi_st *)dev_id;
+
+	/* Read RX FIFO */
+	ssc_read_rx_fifo(spi_st);
+
+	/* Fill TX FIFO */
+	if (spi_st->words_remaining) {
+		ssc_write_tx_fifo(spi_st);
+	} else {
+		/* TX/RX complete */
+		writel_relaxed(0x0, spi_st->base + SSC_IEN);
+		/*
+		 * read SSC_IEN to ensure that this bit is set
+		 * before re-enabling interrupt
+		 */
+		readl(spi_st->base + SSC_IEN);
+		complete(&spi_st->done);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int spi_st_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct spi_master *master;
+	struct resource *res;
+	struct spi_st *spi_st;
+	int irq, ret = 0;
+	u32 var;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*spi_st));
+	if (!master)
+		return -ENOMEM;
+
+	master->dev.of_node		= np;
+	master->mode_bits		= MODEBITS;
+	master->setup			= spi_st_setup;
+	master->cleanup			= spi_st_cleanup;
+	master->transfer_one		= spi_st_transfer_one;
+	master->bits_per_word_mask	= SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
+	master->auto_runtime_pm		= true;
+	master->bus_num			= pdev->id;
+	spi_st				= spi_master_get_devdata(master);
+
+	spi_st->clk = devm_clk_get(&pdev->dev, "ssc");
+	if (IS_ERR(spi_st->clk)) {
+		dev_err(&pdev->dev, "Unable to request clock\n");
+		return PTR_ERR(spi_st->clk);
+	}
+
+	ret = spi_st_clk_enable(spi_st);
+	if (ret)
+		return ret;
+
+	init_completion(&spi_st->done);
+
+	/* Get resources */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	spi_st->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(spi_st->base)) {
+		ret = PTR_ERR(spi_st->base);
+		goto clk_disable;
+	}
+
+	/* Disable I2C and Reset SSC */
+	writel_relaxed(0x0, spi_st->base + SSC_I2C);
+	var = readw_relaxed(spi_st->base + SSC_CTL);
+	var |= SSC_CTL_SR;
+	writel_relaxed(var, spi_st->base + SSC_CTL);
+
+	udelay(1);
+	var = readl_relaxed(spi_st->base + SSC_CTL);
+	var &= ~SSC_CTL_SR;
+	writel_relaxed(var, spi_st->base + SSC_CTL);
+
+	/* Set SSC into slave mode before reconfiguring PIO pins */
+	var = readl_relaxed(spi_st->base + SSC_CTL);
+	var &= ~SSC_CTL_MS;
+	writel_relaxed(var, spi_st->base + SSC_CTL);
+
+	irq = irq_of_parse_and_map(np, 0);
+	if (!irq) {
+		dev_err(&pdev->dev, "IRQ missing or invalid\n");
+		ret = -EINVAL;
+		goto clk_disable;
+	}
+
+	ret = devm_request_irq(&pdev->dev, irq, spi_st_irq, 0,
+			       pdev->name, spi_st);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to request irq %d\n", irq);
+		goto clk_disable;
+	}
+
+	/* by default the device is on */
+	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+
+	platform_set_drvdata(pdev, master);
+
+	ret = devm_spi_register_master(&pdev->dev, master);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register master\n");
+		goto clk_disable;
+	}
+
+	return 0;
+
+clk_disable:
+	spi_st_clk_disable(spi_st);
+
+	return ret;
+}
+
+static int spi_st_remove(struct platform_device *pdev)
+{
+	struct spi_master *master = platform_get_drvdata(pdev);
+	struct spi_st *spi_st = spi_master_get_devdata(master);
+
+	spi_st_clk_disable(spi_st);
+
+	pinctrl_pm_select_sleep_state(&pdev->dev);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int spi_st_runtime_suspend(struct device *dev)
+{
+	struct spi_master *master = dev_get_drvdata(dev);
+	struct spi_st *spi_st = spi_master_get_devdata(master);
+
+	writel_relaxed(0, spi_st->base + SSC_IEN);
+	pinctrl_pm_select_sleep_state(dev);
+
+	spi_st_clk_disable(spi_st);
+
+	return 0;
+}
+
+static int spi_st_runtime_resume(struct device *dev)
+{
+	struct spi_master *master = dev_get_drvdata(dev);
+	struct spi_st *spi_st = spi_master_get_devdata(master);
+	int ret;
+
+	ret = spi_st_clk_enable(spi_st);
+	pinctrl_pm_select_default_state(dev);
+
+	return ret;
+}
+#endif
+
+#ifdef CONFIG_PM_SLEEP
+static int spi_st_suspend(struct device *dev)
+{
+	struct spi_master *master = dev_get_drvdata(dev);
+	int ret;
+
+	ret = spi_master_suspend(master);
+	if (ret)
+		return ret;
+
+	return pm_runtime_force_suspend(dev);
+}
+
+static int spi_st_resume(struct device *dev)
+{
+	struct spi_master *master = dev_get_drvdata(dev);
+	int ret;
+
+	ret = spi_master_resume(master);
+	if (ret)
+		return ret;
+
+	return pm_runtime_force_resume(dev);
+}
+#endif
+
+static const struct dev_pm_ops spi_st_pm = {
+	SET_SYSTEM_SLEEP_PM_OPS(spi_st_suspend, spi_st_resume)
+	SET_RUNTIME_PM_OPS(spi_st_runtime_suspend, spi_st_runtime_resume, NULL)
+};
+
+static struct of_device_id stm_spi_match[] = {
+	{ .compatible = "st,comms-ssc4-spi", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm_spi_match);
+
+static struct platform_driver spi_st_driver = {
+	.driver = {
+		.name = "spi-st",
+		.pm = &spi_st_pm,
+		.of_match_table = of_match_ptr(stm_spi_match),
+	},
+	.probe = spi_st_probe,
+	.remove = spi_st_remove,
+};
+module_platform_driver(spi_st_driver);
+
+MODULE_AUTHOR("Patrice Chotard <[e-mail]>");
+MODULE_DESCRIPTION("STM SSC SPI driver");
+MODULE_LICENSE("GPL v2");