drivers/spi/spi-sun6i.c - kernel/bruno - Git at Google

 /*
  * Copyright (C) 2012 - 2014 Allwinner Tech
  * Pan Nan <pannan@allwinnertech.com>
  *
  * Copyright (C) 2014 Maxime Ripard
  * Maxime Ripard <maxime.ripard@free-electrons.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License 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/device.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/reset.h>

 #include <linux/spi/spi.h>

 #define SUN6I_FIFO_DEPTH		128

 #define SUN6I_GBL_CTL_REG		0x04
 #define SUN6I_GBL_CTL_BUS_ENABLE		BIT(0)
 #define SUN6I_GBL_CTL_MASTER			BIT(1)
 #define SUN6I_GBL_CTL_TP			BIT(7)
 #define SUN6I_GBL_CTL_RST			BIT(31)

 #define SUN6I_TFR_CTL_REG		0x08
 #define SUN6I_TFR_CTL_CPHA			BIT(0)
 #define SUN6I_TFR_CTL_CPOL			BIT(1)
 #define SUN6I_TFR_CTL_SPOL			BIT(2)
 #define SUN6I_TFR_CTL_CS_MASK			0x30
 #define SUN6I_TFR_CTL_CS(cs)			(((cs) << 4) & SUN6I_TFR_CTL_CS_MASK)
 #define SUN6I_TFR_CTL_CS_MANUAL			BIT(6)
 #define SUN6I_TFR_CTL_CS_LEVEL			BIT(7)
 #define SUN6I_TFR_CTL_DHB			BIT(8)
 #define SUN6I_TFR_CTL_FBS			BIT(12)
 #define SUN6I_TFR_CTL_XCH			BIT(31)

 #define SUN6I_INT_CTL_REG		0x10
 #define SUN6I_INT_CTL_RF_OVF			BIT(8)
 #define SUN6I_INT_CTL_TC			BIT(12)

 #define SUN6I_INT_STA_REG		0x14

 #define SUN6I_FIFO_CTL_REG		0x18
 #define SUN6I_FIFO_CTL_RF_RST			BIT(15)
 #define SUN6I_FIFO_CTL_TF_RST			BIT(31)

 #define SUN6I_FIFO_STA_REG		0x1c
 #define SUN6I_FIFO_STA_RF_CNT_MASK		0x7f
 #define SUN6I_FIFO_STA_RF_CNT_BITS		0
 #define SUN6I_FIFO_STA_TF_CNT_MASK		0x7f
 #define SUN6I_FIFO_STA_TF_CNT_BITS		16

 #define SUN6I_CLK_CTL_REG		0x24
 #define SUN6I_CLK_CTL_CDR2_MASK			0xff
 #define SUN6I_CLK_CTL_CDR2(div)			(((div) & SUN6I_CLK_CTL_CDR2_MASK) << 0)
 #define SUN6I_CLK_CTL_CDR1_MASK			0xf
 #define SUN6I_CLK_CTL_CDR1(div)			(((div) & SUN6I_CLK_CTL_CDR1_MASK) << 8)
 #define SUN6I_CLK_CTL_DRS			BIT(12)

 #define SUN6I_BURST_CNT_REG		0x30
 #define SUN6I_BURST_CNT(cnt)			((cnt) & 0xffffff)

 #define SUN6I_XMIT_CNT_REG		0x34
 #define SUN6I_XMIT_CNT(cnt)			((cnt) & 0xffffff)

 #define SUN6I_BURST_CTL_CNT_REG		0x38
 #define SUN6I_BURST_CTL_CNT_STC(cnt)		((cnt) & 0xffffff)

 #define SUN6I_TXDATA_REG		0x200
 #define SUN6I_RXDATA_REG		0x300

 struct sun6i_spi {
 	struct spi_master	*master;
 	void __iomem		*base_addr;
 	struct clk		*hclk;
 	struct clk		*mclk;
 	struct reset_control	*rstc;

 	struct completion	done;

 	const u8		*tx_buf;
 	u8			*rx_buf;
 	int			len;
 };

 static inline u32 sun6i_spi_read(struct sun6i_spi *sspi, u32 reg)
 {
 	return readl(sspi->base_addr + reg);
 }

 static inline void sun6i_spi_write(struct sun6i_spi *sspi, u32 reg, u32 value)
 {
 	writel(value, sspi->base_addr + reg);
 }

 static inline void sun6i_spi_drain_fifo(struct sun6i_spi *sspi, int len)
 {
 	u32 reg, cnt;
 	u8 byte;

 	/* See how much data is available */
 	reg = sun6i_spi_read(sspi, SUN6I_FIFO_STA_REG);
 	reg &= SUN6I_FIFO_STA_RF_CNT_MASK;
 	cnt = reg >> SUN6I_FIFO_STA_RF_CNT_BITS;

 	if (len > cnt)
 		len = cnt;

 	while (len--) {
 		byte = readb(sspi->base_addr + SUN6I_RXDATA_REG);
 		if (sspi->rx_buf)
 			*sspi->rx_buf++ = byte;
 	}
 }

 static inline void sun6i_spi_fill_fifo(struct sun6i_spi *sspi, int len)
 {
 	u8 byte;

 	if (len > sspi->len)
 		len = sspi->len;

 	while (len--) {
 		byte = sspi->tx_buf ? *sspi->tx_buf++ : 0;
 		writeb(byte, sspi->base_addr + SUN6I_TXDATA_REG);
 		sspi->len--;
 	}
 }

 static void sun6i_spi_set_cs(struct spi_device *spi, bool enable)
 {
 	struct sun6i_spi *sspi = spi_master_get_devdata(spi->master);
 	u32 reg;

 	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);
 	reg &= ~SUN6I_TFR_CTL_CS_MASK;
 	reg |= SUN6I_TFR_CTL_CS(spi->chip_select);

 	if (enable)
 		reg |= SUN6I_TFR_CTL_CS_LEVEL;
 	else
 		reg &= ~SUN6I_TFR_CTL_CS_LEVEL;

 	sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg);
 }


 static int sun6i_spi_transfer_one(struct spi_master *master,
 				  struct spi_device *spi,
 				  struct spi_transfer *tfr)
 {
 	struct sun6i_spi *sspi = spi_master_get_devdata(master);
 	unsigned int mclk_rate, div, timeout;
 	unsigned int start, end, tx_time;
 	unsigned int tx_len = 0;
 	int ret = 0;
 	u32 reg;

 	/* We don't support transfer larger than the FIFO */
 	if (tfr->len > SUN6I_FIFO_DEPTH)
 		return -EINVAL;

 	reinit_completion(&sspi->done);
 	sspi->tx_buf = tfr->tx_buf;
 	sspi->rx_buf = tfr->rx_buf;
 	sspi->len = tfr->len;

 	/* Clear pending interrupts */
 	sun6i_spi_write(sspi, SUN6I_INT_STA_REG, ~0);

 	/* Reset FIFO */
 	sun6i_spi_write(sspi, SUN6I_FIFO_CTL_REG,
 			SUN6I_FIFO_CTL_RF_RST | SUN6I_FIFO_CTL_TF_RST);

 	/*
 	 * Setup the transfer control register: Chip Select,
 	 * polarities, etc.
 	 */
 	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);

 	if (spi->mode & SPI_CPOL)
 		reg |= SUN6I_TFR_CTL_CPOL;
 	else
 		reg &= ~SUN6I_TFR_CTL_CPOL;

 	if (spi->mode & SPI_CPHA)
 		reg |= SUN6I_TFR_CTL_CPHA;
 	else
 		reg &= ~SUN6I_TFR_CTL_CPHA;

 	if (spi->mode & SPI_LSB_FIRST)
 		reg |= SUN6I_TFR_CTL_FBS;
 	else
 		reg &= ~SUN6I_TFR_CTL_FBS;

 	/*
 	 * If it's a TX only transfer, we don't want to fill the RX
 	 * FIFO with bogus data
 	 */
 	if (sspi->rx_buf)
 		reg &= ~SUN6I_TFR_CTL_DHB;
 	else
 		reg |= SUN6I_TFR_CTL_DHB;

 	/* We want to control the chip select manually */
 	reg |= SUN6I_TFR_CTL_CS_MANUAL;

 	sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg);

 	/* Ensure that we have a parent clock fast enough */
 	mclk_rate = clk_get_rate(sspi->mclk);
 	if (mclk_rate < (2 * spi->max_speed_hz)) {
 		clk_set_rate(sspi->mclk, 2 * spi->max_speed_hz);
 		mclk_rate = clk_get_rate(sspi->mclk);
 	}

 	/*
 	 * Setup clock divider.
 	 *
 	 * We have two choices there. Either we can use the clock
 	 * divide rate 1, which is calculated thanks to this formula:
 	 * SPI_CLK = MOD_CLK / (2 ^ cdr)
 	 * Or we can use CDR2, which is calculated with the formula:
 	 * SPI_CLK = MOD_CLK / (2 * (cdr + 1))
 	 * Wether we use the former or the latter is set through the
 	 * DRS bit.
 	 *
 	 * First try CDR2, and if we can't reach the expected
 	 * frequency, fall back to CDR1.
 	 */
 	div = mclk_rate / (2 * spi->max_speed_hz);
 	if (div <= (SUN6I_CLK_CTL_CDR2_MASK + 1)) {
 		if (div > 0)
 			div--;

 		reg = SUN6I_CLK_CTL_CDR2(div) | SUN6I_CLK_CTL_DRS;
 	} else {
 		div = ilog2(mclk_rate) - ilog2(spi->max_speed_hz);
 		reg = SUN6I_CLK_CTL_CDR1(div);
 	}

 	sun6i_spi_write(sspi, SUN6I_CLK_CTL_REG, reg);

 	/* Setup the transfer now... */
 	if (sspi->tx_buf)
 		tx_len = tfr->len;

 	/* Setup the counters */
 	sun6i_spi_write(sspi, SUN6I_BURST_CNT_REG, SUN6I_BURST_CNT(tfr->len));
 	sun6i_spi_write(sspi, SUN6I_XMIT_CNT_REG, SUN6I_XMIT_CNT(tx_len));
 	sun6i_spi_write(sspi, SUN6I_BURST_CTL_CNT_REG,
 			SUN6I_BURST_CTL_CNT_STC(tx_len));

 	/* Fill the TX FIFO */
 	sun6i_spi_fill_fifo(sspi, SUN6I_FIFO_DEPTH);

 	/* Enable the interrupts */
 	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, SUN6I_INT_CTL_TC);

 	/* Start the transfer */
 	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);
 	sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg | SUN6I_TFR_CTL_XCH);

 	tx_time = max(tfr->len * 8 * 2 / (tfr->speed_hz / 1000), 100U);
 	start = jiffies;
 	timeout = wait_for_completion_timeout(&sspi->done,
 					      msecs_to_jiffies(tx_time));
 	end = jiffies;
 	if (!timeout) {
 		dev_warn(&master->dev,
 			 "%s: timeout transferring %u bytes@%iHz for %i(%i)ms",
 			 dev_name(&spi->dev), tfr->len, tfr->speed_hz,
 			 jiffies_to_msecs(end - start), tx_time);
 		ret = -ETIMEDOUT;
 		goto out;
 	}

 	sun6i_spi_drain_fifo(sspi, SUN6I_FIFO_DEPTH);

 out:
 	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, 0);

 	return ret;
 }

 static irqreturn_t sun6i_spi_handler(int irq, void *dev_id)
 {
 	struct sun6i_spi *sspi = dev_id;
 	u32 status = sun6i_spi_read(sspi, SUN6I_INT_STA_REG);

 	/* Transfer complete */
 	if (status & SUN6I_INT_CTL_TC) {
 		sun6i_spi_write(sspi, SUN6I_INT_STA_REG, SUN6I_INT_CTL_TC);
 		complete(&sspi->done);
 		return IRQ_HANDLED;
 	}

 	return IRQ_NONE;
 }

 static int sun6i_spi_runtime_resume(struct device *dev)
 {
 	struct spi_master *master = dev_get_drvdata(dev);
 	struct sun6i_spi *sspi = spi_master_get_devdata(master);
 	int ret;

 	ret = clk_prepare_enable(sspi->hclk);
 	if (ret) {
 		dev_err(dev, "Couldn't enable AHB clock\n");
 		goto out;
 	}

 	ret = clk_prepare_enable(sspi->mclk);
 	if (ret) {
 		dev_err(dev, "Couldn't enable module clock\n");
 		goto err;
 	}

 	ret = reset_control_deassert(sspi->rstc);
 	if (ret) {
 		dev_err(dev, "Couldn't deassert the device from reset\n");
 		goto err2;
 	}

 	sun6i_spi_write(sspi, SUN6I_GBL_CTL_REG,
 			SUN6I_GBL_CTL_BUS_ENABLE | SUN6I_GBL_CTL_MASTER | SUN6I_GBL_CTL_TP);

 	return 0;

 err2:
 	clk_disable_unprepare(sspi->mclk);
 err:
 	clk_disable_unprepare(sspi->hclk);
 out:
 	return ret;
 }

 static int sun6i_spi_runtime_suspend(struct device *dev)
 {
 	struct spi_master *master = dev_get_drvdata(dev);
 	struct sun6i_spi *sspi = spi_master_get_devdata(master);

 	reset_control_assert(sspi->rstc);
 	clk_disable_unprepare(sspi->mclk);
 	clk_disable_unprepare(sspi->hclk);

 	return 0;
 }

 static int sun6i_spi_probe(struct platform_device *pdev)
 {
 	struct spi_master *master;
 	struct sun6i_spi *sspi;
 	struct resource	*res;
 	int ret = 0, irq;

 	master = spi_alloc_master(&pdev->dev, sizeof(struct sun6i_spi));
 	if (!master) {
 		dev_err(&pdev->dev, "Unable to allocate SPI Master\n");
 		return -ENOMEM;
 	}

 	platform_set_drvdata(pdev, master);
 	sspi = spi_master_get_devdata(master);

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	sspi->base_addr = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(sspi->base_addr)) {
 		ret = PTR_ERR(sspi->base_addr);
 		goto err_free_master;
 	}

 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0) {
 		dev_err(&pdev->dev, "No spi IRQ specified\n");
 		ret = -ENXIO;
 		goto err_free_master;
 	}

 	ret = devm_request_irq(&pdev->dev, irq, sun6i_spi_handler,
 			       0, "sun6i-spi", sspi);
 	if (ret) {
 		dev_err(&pdev->dev, "Cannot request IRQ\n");
 		goto err_free_master;
 	}

 	sspi->master = master;
 	master->set_cs = sun6i_spi_set_cs;
 	master->transfer_one = sun6i_spi_transfer_one;
 	master->num_chipselect = 4;
 	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LSB_FIRST;
 	master->bits_per_word_mask = SPI_BPW_MASK(8);
 	master->dev.of_node = pdev->dev.of_node;
 	master->auto_runtime_pm = true;

 	sspi->hclk = devm_clk_get(&pdev->dev, "ahb");
 	if (IS_ERR(sspi->hclk)) {
 		dev_err(&pdev->dev, "Unable to acquire AHB clock\n");
 		ret = PTR_ERR(sspi->hclk);
 		goto err_free_master;
 	}

 	sspi->mclk = devm_clk_get(&pdev->dev, "mod");
 	if (IS_ERR(sspi->mclk)) {
 		dev_err(&pdev->dev, "Unable to acquire module clock\n");
 		ret = PTR_ERR(sspi->mclk);
 		goto err_free_master;
 	}

 	init_completion(&sspi->done);

 	sspi->rstc = devm_reset_control_get(&pdev->dev, NULL);
 	if (IS_ERR(sspi->rstc)) {
 		dev_err(&pdev->dev, "Couldn't get reset controller\n");
 		ret = PTR_ERR(sspi->rstc);
 		goto err_free_master;
 	}

 	/*
 	 * This wake-up/shutdown pattern is to be able to have the
 	 * device woken up, even if runtime_pm is disabled
 	 */
 	ret = sun6i_spi_runtime_resume(&pdev->dev);
 	if (ret) {
 		dev_err(&pdev->dev, "Couldn't resume the device\n");
 		goto err_free_master;
 	}

 	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
 	pm_runtime_idle(&pdev->dev);

 	ret = devm_spi_register_master(&pdev->dev, master);
 	if (ret) {
 		dev_err(&pdev->dev, "cannot register SPI master\n");
 		goto err_pm_disable;
 	}

 	return 0;

 err_pm_disable:
 	pm_runtime_disable(&pdev->dev);
 	sun6i_spi_runtime_suspend(&pdev->dev);
 err_free_master:
 	spi_master_put(master);
 	return ret;
 }

 static int sun6i_spi_remove(struct platform_device *pdev)
 {
 	pm_runtime_disable(&pdev->dev);

 	return 0;
 }

 static const struct of_device_id sun6i_spi_match[] = {
 	{ .compatible = "allwinner,sun6i-a31-spi", },
 	{}
 };
 MODULE_DEVICE_TABLE(of, sun6i_spi_match);

 static const struct dev_pm_ops sun6i_spi_pm_ops = {
 	.runtime_resume		= sun6i_spi_runtime_resume,
 	.runtime_suspend	= sun6i_spi_runtime_suspend,
 };

 static struct platform_driver sun6i_spi_driver = {
 	.probe	= sun6i_spi_probe,
 	.remove	= sun6i_spi_remove,
 	.driver	= {
 		.name		= "sun6i-spi",
 		.of_match_table	= sun6i_spi_match,
 		.pm		= &sun6i_spi_pm_ops,
 	},
 };
 module_platform_driver(sun6i_spi_driver);

 MODULE_AUTHOR("Pan Nan <pannan@allwinnertech.com>");
 MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
 MODULE_DESCRIPTION("Allwinner A31 SPI controller driver");
 MODULE_LICENSE("GPL");
	/*
	* Copyright (C) 2012 - 2014 Allwinner Tech
	* Pan Nan <pannan@allwinnertech.com>
	*
	* Copyright (C) 2014 Maxime Ripard
	* Maxime Ripard <maxime.ripard@free-electrons.com>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License 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/device.h>
	#include <linux/interrupt.h>
	#include <linux/io.h>
	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/pm_runtime.h>
	#include <linux/reset.h>

	#include <linux/spi/spi.h>

	#define SUN6I_FIFO_DEPTH 128

	#define SUN6I_GBL_CTL_REG 0x04
	#define SUN6I_GBL_CTL_BUS_ENABLE BIT(0)
	#define SUN6I_GBL_CTL_MASTER BIT(1)
	#define SUN6I_GBL_CTL_TP BIT(7)
	#define SUN6I_GBL_CTL_RST BIT(31)

	#define SUN6I_TFR_CTL_REG 0x08
	#define SUN6I_TFR_CTL_CPHA BIT(0)
	#define SUN6I_TFR_CTL_CPOL BIT(1)
	#define SUN6I_TFR_CTL_SPOL BIT(2)
	#define SUN6I_TFR_CTL_CS_MASK 0x30
	#define SUN6I_TFR_CTL_CS(cs) (((cs) << 4) & SUN6I_TFR_CTL_CS_MASK)
	#define SUN6I_TFR_CTL_CS_MANUAL BIT(6)
	#define SUN6I_TFR_CTL_CS_LEVEL BIT(7)
	#define SUN6I_TFR_CTL_DHB BIT(8)
	#define SUN6I_TFR_CTL_FBS BIT(12)
	#define SUN6I_TFR_CTL_XCH BIT(31)

	#define SUN6I_INT_CTL_REG 0x10
	#define SUN6I_INT_CTL_RF_OVF BIT(8)
	#define SUN6I_INT_CTL_TC BIT(12)

	#define SUN6I_INT_STA_REG 0x14

	#define SUN6I_FIFO_CTL_REG 0x18
	#define SUN6I_FIFO_CTL_RF_RST BIT(15)
	#define SUN6I_FIFO_CTL_TF_RST BIT(31)

	#define SUN6I_FIFO_STA_REG 0x1c
	#define SUN6I_FIFO_STA_RF_CNT_MASK 0x7f
	#define SUN6I_FIFO_STA_RF_CNT_BITS 0
	#define SUN6I_FIFO_STA_TF_CNT_MASK 0x7f
	#define SUN6I_FIFO_STA_TF_CNT_BITS 16

	#define SUN6I_CLK_CTL_REG 0x24
	#define SUN6I_CLK_CTL_CDR2_MASK 0xff
	#define SUN6I_CLK_CTL_CDR2(div) (((div) & SUN6I_CLK_CTL_CDR2_MASK) << 0)
	#define SUN6I_CLK_CTL_CDR1_MASK 0xf
	#define SUN6I_CLK_CTL_CDR1(div) (((div) & SUN6I_CLK_CTL_CDR1_MASK) << 8)
	#define SUN6I_CLK_CTL_DRS BIT(12)

	#define SUN6I_BURST_CNT_REG 0x30
	#define SUN6I_BURST_CNT(cnt) ((cnt) & 0xffffff)

	#define SUN6I_XMIT_CNT_REG 0x34
	#define SUN6I_XMIT_CNT(cnt) ((cnt) & 0xffffff)

	#define SUN6I_BURST_CTL_CNT_REG 0x38
	#define SUN6I_BURST_CTL_CNT_STC(cnt) ((cnt) & 0xffffff)

	#define SUN6I_TXDATA_REG 0x200
	#define SUN6I_RXDATA_REG 0x300

	struct sun6i_spi {
	struct spi_master *master;
	void __iomem *base_addr;
	struct clk *hclk;
	struct clk *mclk;
	struct reset_control *rstc;

	struct completion done;

	const u8 *tx_buf;
	u8 *rx_buf;
	int len;
	};

	static inline u32 sun6i_spi_read(struct sun6i_spi *sspi, u32 reg)
	{
	return readl(sspi->base_addr + reg);
	}

	static inline void sun6i_spi_write(struct sun6i_spi *sspi, u32 reg, u32 value)
	{
	writel(value, sspi->base_addr + reg);
	}

	static inline void sun6i_spi_drain_fifo(struct sun6i_spi *sspi, int len)
	{
	u32 reg, cnt;
	u8 byte;

	/* See how much data is available */
	reg = sun6i_spi_read(sspi, SUN6I_FIFO_STA_REG);
	reg &= SUN6I_FIFO_STA_RF_CNT_MASK;
	cnt = reg >> SUN6I_FIFO_STA_RF_CNT_BITS;

	if (len > cnt)
	len = cnt;

	while (len--) {
	byte = readb(sspi->base_addr + SUN6I_RXDATA_REG);
	if (sspi->rx_buf)
	*sspi->rx_buf++ = byte;
	}
	}

	static inline void sun6i_spi_fill_fifo(struct sun6i_spi *sspi, int len)
	{
	u8 byte;

	if (len > sspi->len)
	len = sspi->len;

	while (len--) {
	byte = sspi->tx_buf ? *sspi->tx_buf++ : 0;
	writeb(byte, sspi->base_addr + SUN6I_TXDATA_REG);
	sspi->len--;
	}
	}

	static void sun6i_spi_set_cs(struct spi_device *spi, bool enable)
	{
	struct sun6i_spi *sspi = spi_master_get_devdata(spi->master);
	u32 reg;

	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);
	reg &= ~SUN6I_TFR_CTL_CS_MASK;
	reg \|= SUN6I_TFR_CTL_CS(spi->chip_select);

	if (enable)
	reg \|= SUN6I_TFR_CTL_CS_LEVEL;
	else
	reg &= ~SUN6I_TFR_CTL_CS_LEVEL;

	sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg);
	}


	static int sun6i_spi_transfer_one(struct spi_master *master,
	struct spi_device *spi,
	struct spi_transfer *tfr)
	{
	struct sun6i_spi *sspi = spi_master_get_devdata(master);
	unsigned int mclk_rate, div, timeout;
	unsigned int start, end, tx_time;
	unsigned int tx_len = 0;
	int ret = 0;
	u32 reg;

	/* We don't support transfer larger than the FIFO */
	if (tfr->len > SUN6I_FIFO_DEPTH)
	return -EINVAL;

	reinit_completion(&sspi->done);
	sspi->tx_buf = tfr->tx_buf;
	sspi->rx_buf = tfr->rx_buf;
	sspi->len = tfr->len;

	/* Clear pending interrupts */
	sun6i_spi_write(sspi, SUN6I_INT_STA_REG, ~0);

	/* Reset FIFO */
	sun6i_spi_write(sspi, SUN6I_FIFO_CTL_REG,
	SUN6I_FIFO_CTL_RF_RST \| SUN6I_FIFO_CTL_TF_RST);

	/*
	* Setup the transfer control register: Chip Select,
	* polarities, etc.
	*/
	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);

	if (spi->mode & SPI_CPOL)
	reg \|= SUN6I_TFR_CTL_CPOL;
	else
	reg &= ~SUN6I_TFR_CTL_CPOL;

	if (spi->mode & SPI_CPHA)
	reg \|= SUN6I_TFR_CTL_CPHA;
	else
	reg &= ~SUN6I_TFR_CTL_CPHA;

	if (spi->mode & SPI_LSB_FIRST)
	reg \|= SUN6I_TFR_CTL_FBS;
	else
	reg &= ~SUN6I_TFR_CTL_FBS;

	/*
	* If it's a TX only transfer, we don't want to fill the RX
	* FIFO with bogus data
	*/
	if (sspi->rx_buf)
	reg &= ~SUN6I_TFR_CTL_DHB;
	else
	reg \|= SUN6I_TFR_CTL_DHB;

	/* We want to control the chip select manually */
	reg \|= SUN6I_TFR_CTL_CS_MANUAL;

	sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg);

	/* Ensure that we have a parent clock fast enough */
	mclk_rate = clk_get_rate(sspi->mclk);
	if (mclk_rate < (2 * spi->max_speed_hz)) {
	clk_set_rate(sspi->mclk, 2 * spi->max_speed_hz);
	mclk_rate = clk_get_rate(sspi->mclk);
	}

	/*
	* Setup clock divider.
	*
	* We have two choices there. Either we can use the clock
	* divide rate 1, which is calculated thanks to this formula:
	* SPI_CLK = MOD_CLK / (2 ^ cdr)
	* Or we can use CDR2, which is calculated with the formula:
	* SPI_CLK = MOD_CLK / (2 * (cdr + 1))
	* Wether we use the former or the latter is set through the
	* DRS bit.
	*
	* First try CDR2, and if we can't reach the expected
	* frequency, fall back to CDR1.
	*/
	div = mclk_rate / (2 * spi->max_speed_hz);
	if (div <= (SUN6I_CLK_CTL_CDR2_MASK + 1)) {
	if (div > 0)
	div--;

	reg = SUN6I_CLK_CTL_CDR2(div) \| SUN6I_CLK_CTL_DRS;
	} else {
	div = ilog2(mclk_rate) - ilog2(spi->max_speed_hz);
	reg = SUN6I_CLK_CTL_CDR1(div);
	}

	sun6i_spi_write(sspi, SUN6I_CLK_CTL_REG, reg);

	/* Setup the transfer now... */
	if (sspi->tx_buf)
	tx_len = tfr->len;

	/* Setup the counters */
	sun6i_spi_write(sspi, SUN6I_BURST_CNT_REG, SUN6I_BURST_CNT(tfr->len));
	sun6i_spi_write(sspi, SUN6I_XMIT_CNT_REG, SUN6I_XMIT_CNT(tx_len));
	sun6i_spi_write(sspi, SUN6I_BURST_CTL_CNT_REG,
	SUN6I_BURST_CTL_CNT_STC(tx_len));

	/* Fill the TX FIFO */
	sun6i_spi_fill_fifo(sspi, SUN6I_FIFO_DEPTH);

	/* Enable the interrupts */
	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, SUN6I_INT_CTL_TC);

	/* Start the transfer */
	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);
	sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg \| SUN6I_TFR_CTL_XCH);

	tx_time = max(tfr->len * 8 * 2 / (tfr->speed_hz / 1000), 100U);
	start = jiffies;
	timeout = wait_for_completion_timeout(&sspi->done,
	msecs_to_jiffies(tx_time));
	end = jiffies;
	if (!timeout) {
	dev_warn(&master->dev,
	"%s: timeout transferring %u bytes@%iHz for %i(%i)ms",
	dev_name(&spi->dev), tfr->len, tfr->speed_hz,
	jiffies_to_msecs(end - start), tx_time);
	ret = -ETIMEDOUT;
	goto out;
	}

	sun6i_spi_drain_fifo(sspi, SUN6I_FIFO_DEPTH);

	out:
	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, 0);

	return ret;
	}

	static irqreturn_t sun6i_spi_handler(int irq, void *dev_id)
	{
	struct sun6i_spi *sspi = dev_id;
	u32 status = sun6i_spi_read(sspi, SUN6I_INT_STA_REG);

	/* Transfer complete */
	if (status & SUN6I_INT_CTL_TC) {
	sun6i_spi_write(sspi, SUN6I_INT_STA_REG, SUN6I_INT_CTL_TC);
	complete(&sspi->done);
	return IRQ_HANDLED;
	}

	return IRQ_NONE;
	}

	static int sun6i_spi_runtime_resume(struct device *dev)
	{
	struct spi_master *master = dev_get_drvdata(dev);
	struct sun6i_spi *sspi = spi_master_get_devdata(master);
	int ret;

	ret = clk_prepare_enable(sspi->hclk);
	if (ret) {
	dev_err(dev, "Couldn't enable AHB clock\n");
	goto out;
	}

	ret = clk_prepare_enable(sspi->mclk);
	if (ret) {
	dev_err(dev, "Couldn't enable module clock\n");
	goto err;
	}

	ret = reset_control_deassert(sspi->rstc);
	if (ret) {
	dev_err(dev, "Couldn't deassert the device from reset\n");
	goto err2;
	}

	sun6i_spi_write(sspi, SUN6I_GBL_CTL_REG,
	SUN6I_GBL_CTL_BUS_ENABLE \| SUN6I_GBL_CTL_MASTER \| SUN6I_GBL_CTL_TP);

	return 0;

	err2:
	clk_disable_unprepare(sspi->mclk);
	err:
	clk_disable_unprepare(sspi->hclk);
	out:
	return ret;
	}

	static int sun6i_spi_runtime_suspend(struct device *dev)
	{
	struct spi_master *master = dev_get_drvdata(dev);
	struct sun6i_spi *sspi = spi_master_get_devdata(master);

	reset_control_assert(sspi->rstc);
	clk_disable_unprepare(sspi->mclk);
	clk_disable_unprepare(sspi->hclk);

	return 0;
	}

	static int sun6i_spi_probe(struct platform_device *pdev)
	{
	struct spi_master *master;
	struct sun6i_spi *sspi;
	struct resource *res;
	int ret = 0, irq;

	master = spi_alloc_master(&pdev->dev, sizeof(struct sun6i_spi));
	if (!master) {
	dev_err(&pdev->dev, "Unable to allocate SPI Master\n");
	return -ENOMEM;
	}

	platform_set_drvdata(pdev, master);
	sspi = spi_master_get_devdata(master);

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	sspi->base_addr = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(sspi->base_addr)) {
	ret = PTR_ERR(sspi->base_addr);
	goto err_free_master;
	}

	irq = platform_get_irq(pdev, 0);
	if (irq < 0) {
	dev_err(&pdev->dev, "No spi IRQ specified\n");
	ret = -ENXIO;
	goto err_free_master;
	}

	ret = devm_request_irq(&pdev->dev, irq, sun6i_spi_handler,
	0, "sun6i-spi", sspi);
	if (ret) {
	dev_err(&pdev->dev, "Cannot request IRQ\n");
	goto err_free_master;
	}

	sspi->master = master;
	master->set_cs = sun6i_spi_set_cs;
	master->transfer_one = sun6i_spi_transfer_one;
	master->num_chipselect = 4;
	master->mode_bits = SPI_CPOL \| SPI_CPHA \| SPI_CS_HIGH \| SPI_LSB_FIRST;
	master->bits_per_word_mask = SPI_BPW_MASK(8);
	master->dev.of_node = pdev->dev.of_node;
	master->auto_runtime_pm = true;

	sspi->hclk = devm_clk_get(&pdev->dev, "ahb");
	if (IS_ERR(sspi->hclk)) {
	dev_err(&pdev->dev, "Unable to acquire AHB clock\n");
	ret = PTR_ERR(sspi->hclk);
	goto err_free_master;
	}

	sspi->mclk = devm_clk_get(&pdev->dev, "mod");
	if (IS_ERR(sspi->mclk)) {
	dev_err(&pdev->dev, "Unable to acquire module clock\n");
	ret = PTR_ERR(sspi->mclk);
	goto err_free_master;
	}

	init_completion(&sspi->done);

	sspi->rstc = devm_reset_control_get(&pdev->dev, NULL);
	if (IS_ERR(sspi->rstc)) {
	dev_err(&pdev->dev, "Couldn't get reset controller\n");
	ret = PTR_ERR(sspi->rstc);
	goto err_free_master;
	}

	/*
	* This wake-up/shutdown pattern is to be able to have the
	* device woken up, even if runtime_pm is disabled
	*/
	ret = sun6i_spi_runtime_resume(&pdev->dev);
	if (ret) {
	dev_err(&pdev->dev, "Couldn't resume the device\n");
	goto err_free_master;
	}

	pm_runtime_set_active(&pdev->dev);
	pm_runtime_enable(&pdev->dev);
	pm_runtime_idle(&pdev->dev);

	ret = devm_spi_register_master(&pdev->dev, master);
	if (ret) {
	dev_err(&pdev->dev, "cannot register SPI master\n");
	goto err_pm_disable;
	}

	return 0;

	err_pm_disable:
	pm_runtime_disable(&pdev->dev);
	sun6i_spi_runtime_suspend(&pdev->dev);
	err_free_master:
	spi_master_put(master);
	return ret;
	}

	static int sun6i_spi_remove(struct platform_device *pdev)
	{
	pm_runtime_disable(&pdev->dev);

	return 0;
	}

	static const struct of_device_id sun6i_spi_match[] = {
	{ .compatible = "allwinner,sun6i-a31-spi", },
	{}
	};
	MODULE_DEVICE_TABLE(of, sun6i_spi_match);

	static const struct dev_pm_ops sun6i_spi_pm_ops = {
	.runtime_resume = sun6i_spi_runtime_resume,
	.runtime_suspend = sun6i_spi_runtime_suspend,
	};

	static struct platform_driver sun6i_spi_driver = {
	.probe = sun6i_spi_probe,
	.remove = sun6i_spi_remove,
	.driver = {
	.name = "sun6i-spi",
	.of_match_table = sun6i_spi_match,
	.pm = &sun6i_spi_pm_ops,
	},
	};
	module_platform_driver(sun6i_spi_driver);

	MODULE_AUTHOR("Pan Nan <pannan@allwinnertech.com>");
	MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
	MODULE_DESCRIPTION("Allwinner A31 SPI controller driver");
	MODULE_LICENSE("GPL");