drivers/spi/spi-meson-spifc.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 //
 // Driver for Amlogic Meson SPI flash controller (SPIFC)
 //
 // Copyright (C) 2014 Beniamino Galvani <b.galvani@gmail.com>
 //

 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/spi/spi.h>
 #include <linux/types.h>

 /* register map */
 #define REG_CMD			0x00
 #define REG_ADDR		0x04
 #define REG_CTRL		0x08
 #define REG_CTRL1		0x0c
 #define REG_STATUS		0x10
 #define REG_CTRL2		0x14
 #define REG_CLOCK		0x18
 #define REG_USER		0x1c
 #define REG_USER1		0x20
 #define REG_USER2		0x24
 #define REG_USER3		0x28
 #define REG_USER4		0x2c
 #define REG_SLAVE		0x30
 #define REG_SLAVE1		0x34
 #define REG_SLAVE2		0x38
 #define REG_SLAVE3		0x3c
 #define REG_C0			0x40
 #define REG_B8			0x60
 #define REG_MAX			0x7c

 /* register fields */
 #define CMD_USER		BIT(18)
 #define CTRL_ENABLE_AHB		BIT(17)
 #define CLOCK_SOURCE		BIT(31)
 #define CLOCK_DIV_SHIFT		12
 #define CLOCK_DIV_MASK		(0x3f << CLOCK_DIV_SHIFT)
 #define CLOCK_CNT_HIGH_SHIFT	6
 #define CLOCK_CNT_HIGH_MASK	(0x3f << CLOCK_CNT_HIGH_SHIFT)
 #define CLOCK_CNT_LOW_SHIFT	0
 #define CLOCK_CNT_LOW_MASK	(0x3f << CLOCK_CNT_LOW_SHIFT)
 #define USER_DIN_EN_MS		BIT(0)
 #define USER_CMP_MODE		BIT(2)
 #define USER_UC_DOUT_SEL	BIT(27)
 #define USER_UC_DIN_SEL		BIT(28)
 #define USER_UC_MASK		((BIT(5) - 1) << 27)
 #define USER1_BN_UC_DOUT_SHIFT	17
 #define USER1_BN_UC_DOUT_MASK	(0xff << 16)
 #define USER1_BN_UC_DIN_SHIFT	8
 #define USER1_BN_UC_DIN_MASK	(0xff << 8)
 #define USER4_CS_ACT		BIT(30)
 #define SLAVE_TRST_DONE		BIT(4)
 #define SLAVE_OP_MODE		BIT(30)
 #define SLAVE_SW_RST		BIT(31)

 #define SPIFC_BUFFER_SIZE	64

 /**
  * struct meson_spifc
  * @master:	the SPI master
  * @regmap:	regmap for device registers
  * @clk:	input clock of the built-in baud rate generator
  * @dev:	the device structure
  */
 struct meson_spifc {
 	struct spi_master *master;
 	struct regmap *regmap;
 	struct clk *clk;
 	struct device *dev;
 };

 static const struct regmap_config spifc_regmap_config = {
 	.reg_bits = 32,
 	.val_bits = 32,
 	.reg_stride = 4,
 	.max_register = REG_MAX,
 };

 /**
  * meson_spifc_wait_ready() - wait for the current operation to terminate
  * @spifc:	the Meson SPI device
  * Return:	0 on success, a negative value on error
  */
 static int meson_spifc_wait_ready(struct meson_spifc *spifc)
 {
 	unsigned long deadline = jiffies + msecs_to_jiffies(5);
 	u32 data;

 	do {
 		regmap_read(spifc->regmap, REG_SLAVE, &data);
 		if (data & SLAVE_TRST_DONE)
 			return 0;
 		cond_resched();
 	} while (!time_after(jiffies, deadline));

 	return -ETIMEDOUT;
 }

 /**
  * meson_spifc_drain_buffer() - copy data from device buffer to memory
  * @spifc:	the Meson SPI device
  * @buf:	the destination buffer
  * @len:	number of bytes to copy
  */
 static void meson_spifc_drain_buffer(struct meson_spifc *spifc, u8 *buf,
 				     int len)
 {
 	u32 data;
 	int i = 0;

 	while (i < len) {
 		regmap_read(spifc->regmap, REG_C0 + i, &data);

 		if (len - i >= 4) {
 			*((u32 *)buf) = data;
 			buf += 4;
 		} else {
 			memcpy(buf, &data, len - i);
 			break;
 		}
 		i += 4;
 	}
 }

 /**
  * meson_spifc_fill_buffer() - copy data from memory to device buffer
  * @spifc:	the Meson SPI device
  * @buf:	the source buffer
  * @len:	number of bytes to copy
  */
 static void meson_spifc_fill_buffer(struct meson_spifc *spifc, const u8 *buf,
 				    int len)
 {
 	u32 data;
 	int i = 0;

 	while (i < len) {
 		if (len - i >= 4)
 			data = *(u32 *)buf;
 		else
 			memcpy(&data, buf, len - i);

 		regmap_write(spifc->regmap, REG_C0 + i, data);

 		buf += 4;
 		i += 4;
 	}
 }

 /**
  * meson_spifc_setup_speed() - program the clock divider
  * @spifc:	the Meson SPI device
  * @speed:	desired speed in Hz
  */
 static void meson_spifc_setup_speed(struct meson_spifc *spifc, u32 speed)
 {
 	unsigned long parent, value;
 	int n;

 	parent = clk_get_rate(spifc->clk);
 	n = max_t(int, parent / speed - 1, 1);

 	dev_dbg(spifc->dev, "parent %lu, speed %u, n %d\n", parent,
 		speed, n);

 	value = (n << CLOCK_DIV_SHIFT) & CLOCK_DIV_MASK;
 	value |= (n << CLOCK_CNT_LOW_SHIFT) & CLOCK_CNT_LOW_MASK;
 	value |= (((n + 1) / 2 - 1) << CLOCK_CNT_HIGH_SHIFT) &
 		CLOCK_CNT_HIGH_MASK;

 	regmap_write(spifc->regmap, REG_CLOCK, value);
 }

 /**
  * meson_spifc_txrx() - transfer a chunk of data
  * @spifc:	the Meson SPI device
  * @xfer:	the current SPI transfer
  * @offset:	offset of the data to transfer
  * @len:	length of the data to transfer
  * @last_xfer:	whether this is the last transfer of the message
  * @last_chunk:	whether this is the last chunk of the transfer
  * Return:	0 on success, a negative value on error
  */
 static int meson_spifc_txrx(struct meson_spifc *spifc,
 			    struct spi_transfer *xfer,
 			    int offset, int len, bool last_xfer,
 			    bool last_chunk)
 {
 	bool keep_cs = true;
 	int ret;

 	if (xfer->tx_buf)
 		meson_spifc_fill_buffer(spifc, xfer->tx_buf + offset, len);

 	/* enable DOUT stage */
 	regmap_update_bits(spifc->regmap, REG_USER, USER_UC_MASK,
 			   USER_UC_DOUT_SEL);
 	regmap_write(spifc->regmap, REG_USER1,
 		     (8 * len - 1) << USER1_BN_UC_DOUT_SHIFT);

 	/* enable data input during DOUT */
 	regmap_update_bits(spifc->regmap, REG_USER, USER_DIN_EN_MS,
 			   USER_DIN_EN_MS);

 	if (last_chunk) {
 		if (last_xfer)
 			keep_cs = xfer->cs_change;
 		else
 			keep_cs = !xfer->cs_change;
 	}

 	regmap_update_bits(spifc->regmap, REG_USER4, USER4_CS_ACT,
 			   keep_cs ? USER4_CS_ACT : 0);

 	/* clear transition done bit */
 	regmap_update_bits(spifc->regmap, REG_SLAVE, SLAVE_TRST_DONE, 0);
 	/* start transfer */
 	regmap_update_bits(spifc->regmap, REG_CMD, CMD_USER, CMD_USER);

 	ret = meson_spifc_wait_ready(spifc);

 	if (!ret && xfer->rx_buf)
 		meson_spifc_drain_buffer(spifc, xfer->rx_buf + offset, len);

 	return ret;
 }

 /**
  * meson_spifc_transfer_one() - perform a single transfer
  * @master:	the SPI master
  * @spi:	the SPI device
  * @xfer:	the current SPI transfer
  * Return:	0 on success, a negative value on error
  */
 static int meson_spifc_transfer_one(struct spi_master *master,
 				    struct spi_device *spi,
 				    struct spi_transfer *xfer)
 {
 	struct meson_spifc *spifc = spi_master_get_devdata(master);
 	int len, done = 0, ret = 0;

 	meson_spifc_setup_speed(spifc, xfer->speed_hz);

 	regmap_update_bits(spifc->regmap, REG_CTRL, CTRL_ENABLE_AHB, 0);

 	while (done < xfer->len && !ret) {
 		len = min_t(int, xfer->len - done, SPIFC_BUFFER_SIZE);
 		ret = meson_spifc_txrx(spifc, xfer, done, len,
 				       spi_transfer_is_last(master, xfer),
 				       done + len >= xfer->len);
 		done += len;
 	}

 	regmap_update_bits(spifc->regmap, REG_CTRL, CTRL_ENABLE_AHB,
 			   CTRL_ENABLE_AHB);

 	return ret;
 }

 /**
  * meson_spifc_hw_init() - reset and initialize the SPI controller
  * @spifc:	the Meson SPI device
  */
 static void meson_spifc_hw_init(struct meson_spifc *spifc)
 {
 	/* reset device */
 	regmap_update_bits(spifc->regmap, REG_SLAVE, SLAVE_SW_RST,
 			   SLAVE_SW_RST);
 	/* disable compatible mode */
 	regmap_update_bits(spifc->regmap, REG_USER, USER_CMP_MODE, 0);
 	/* set master mode */
 	regmap_update_bits(spifc->regmap, REG_SLAVE, SLAVE_OP_MODE, 0);
 }

 static int meson_spifc_probe(struct platform_device *pdev)
 {
 	struct spi_master *master;
 	struct meson_spifc *spifc;
 	void __iomem *base;
 	unsigned int rate;
 	int ret = 0;

 	master = spi_alloc_master(&pdev->dev, sizeof(struct meson_spifc));
 	if (!master)
 		return -ENOMEM;

 	platform_set_drvdata(pdev, master);

 	spifc = spi_master_get_devdata(master);
 	spifc->dev = &pdev->dev;

 	base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(base)) {
 		ret = PTR_ERR(base);
 		goto out_err;
 	}

 	spifc->regmap = devm_regmap_init_mmio(spifc->dev, base,
 					      &spifc_regmap_config);
 	if (IS_ERR(spifc->regmap)) {
 		ret = PTR_ERR(spifc->regmap);
 		goto out_err;
 	}

 	spifc->clk = devm_clk_get(spifc->dev, NULL);
 	if (IS_ERR(spifc->clk)) {
 		dev_err(spifc->dev, "missing clock\n");
 		ret = PTR_ERR(spifc->clk);
 		goto out_err;
 	}

 	ret = clk_prepare_enable(spifc->clk);
 	if (ret) {
 		dev_err(spifc->dev, "can't prepare clock\n");
 		goto out_err;
 	}

 	rate = clk_get_rate(spifc->clk);

 	master->num_chipselect = 1;
 	master->dev.of_node = pdev->dev.of_node;
 	master->bits_per_word_mask = SPI_BPW_MASK(8);
 	master->auto_runtime_pm = true;
 	master->transfer_one = meson_spifc_transfer_one;
 	master->min_speed_hz = rate >> 6;
 	master->max_speed_hz = rate >> 1;

 	meson_spifc_hw_init(spifc);

 	pm_runtime_set_active(spifc->dev);
 	pm_runtime_enable(spifc->dev);

 	ret = devm_spi_register_master(spifc->dev, master);
 	if (ret) {
 		dev_err(spifc->dev, "failed to register spi master\n");
 		goto out_clk;
 	}

 	return 0;
 out_clk:
 	clk_disable_unprepare(spifc->clk);
 	pm_runtime_disable(spifc->dev);
 out_err:
 	spi_master_put(master);
 	return ret;
 }

 static int meson_spifc_remove(struct platform_device *pdev)
 {
 	struct spi_master *master = platform_get_drvdata(pdev);
 	struct meson_spifc *spifc = spi_master_get_devdata(master);

 	pm_runtime_get_sync(&pdev->dev);
 	clk_disable_unprepare(spifc->clk);
 	pm_runtime_disable(&pdev->dev);

 	return 0;
 }

 #ifdef CONFIG_PM_SLEEP
 static int meson_spifc_suspend(struct device *dev)
 {
 	struct spi_master *master = dev_get_drvdata(dev);
 	struct meson_spifc *spifc = spi_master_get_devdata(master);
 	int ret;

 	ret = spi_master_suspend(master);
 	if (ret)
 		return ret;

 	if (!pm_runtime_suspended(dev))
 		clk_disable_unprepare(spifc->clk);

 	return 0;
 }

 static int meson_spifc_resume(struct device *dev)
 {
 	struct spi_master *master = dev_get_drvdata(dev);
 	struct meson_spifc *spifc = spi_master_get_devdata(master);
 	int ret;

 	if (!pm_runtime_suspended(dev)) {
 		ret = clk_prepare_enable(spifc->clk);
 		if (ret)
 			return ret;
 	}

 	meson_spifc_hw_init(spifc);

 	ret = spi_master_resume(master);
 	if (ret)
 		clk_disable_unprepare(spifc->clk);

 	return ret;
 }
 #endif /* CONFIG_PM_SLEEP */

 #ifdef CONFIG_PM
 static int meson_spifc_runtime_suspend(struct device *dev)
 {
 	struct spi_master *master = dev_get_drvdata(dev);
 	struct meson_spifc *spifc = spi_master_get_devdata(master);

 	clk_disable_unprepare(spifc->clk);

 	return 0;
 }

 static int meson_spifc_runtime_resume(struct device *dev)
 {
 	struct spi_master *master = dev_get_drvdata(dev);
 	struct meson_spifc *spifc = spi_master_get_devdata(master);

 	return clk_prepare_enable(spifc->clk);
 }
 #endif /* CONFIG_PM */

 static const struct dev_pm_ops meson_spifc_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(meson_spifc_suspend, meson_spifc_resume)
 	SET_RUNTIME_PM_OPS(meson_spifc_runtime_suspend,
 			   meson_spifc_runtime_resume,
 			   NULL)
 };

 static const struct of_device_id meson_spifc_dt_match[] = {
 	{ .compatible = "amlogic,meson6-spifc", },
 	{ .compatible = "amlogic,meson-gxbb-spifc", },
 	{ },
 };
 MODULE_DEVICE_TABLE(of, meson_spifc_dt_match);

 static struct platform_driver meson_spifc_driver = {
 	.probe	= meson_spifc_probe,
 	.remove	= meson_spifc_remove,
 	.driver	= {
 		.name		= "meson-spifc",
 		.of_match_table	= of_match_ptr(meson_spifc_dt_match),
 		.pm		= &meson_spifc_pm_ops,
 	},
 };

 module_platform_driver(meson_spifc_driver);

 MODULE_AUTHOR("Beniamino Galvani <b.galvani@gmail.com>");
 MODULE_DESCRIPTION("Amlogic Meson SPIFC driver");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0+
	//
	// Driver for Amlogic Meson SPI flash controller (SPIFC)
	//
	// Copyright (C) 2014 Beniamino Galvani <b.galvani@gmail.com>
	//

	#include <linux/clk.h>
	#include <linux/delay.h>
	#include <linux/device.h>
	#include <linux/io.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/platform_device.h>
	#include <linux/pm_runtime.h>
	#include <linux/regmap.h>
	#include <linux/spi/spi.h>
	#include <linux/types.h>

	/* register map */
	#define REG_CMD 0x00
	#define REG_ADDR 0x04
	#define REG_CTRL 0x08
	#define REG_CTRL1 0x0c
	#define REG_STATUS 0x10
	#define REG_CTRL2 0x14
	#define REG_CLOCK 0x18
	#define REG_USER 0x1c
	#define REG_USER1 0x20
	#define REG_USER2 0x24
	#define REG_USER3 0x28
	#define REG_USER4 0x2c
	#define REG_SLAVE 0x30
	#define REG_SLAVE1 0x34
	#define REG_SLAVE2 0x38
	#define REG_SLAVE3 0x3c
	#define REG_C0 0x40
	#define REG_B8 0x60
	#define REG_MAX 0x7c

	/* register fields */
	#define CMD_USER BIT(18)
	#define CTRL_ENABLE_AHB BIT(17)
	#define CLOCK_SOURCE BIT(31)
	#define CLOCK_DIV_SHIFT 12
	#define CLOCK_DIV_MASK (0x3f << CLOCK_DIV_SHIFT)
	#define CLOCK_CNT_HIGH_SHIFT 6
	#define CLOCK_CNT_HIGH_MASK (0x3f << CLOCK_CNT_HIGH_SHIFT)
	#define CLOCK_CNT_LOW_SHIFT 0
	#define CLOCK_CNT_LOW_MASK (0x3f << CLOCK_CNT_LOW_SHIFT)
	#define USER_DIN_EN_MS BIT(0)
	#define USER_CMP_MODE BIT(2)
	#define USER_UC_DOUT_SEL BIT(27)
	#define USER_UC_DIN_SEL BIT(28)
	#define USER_UC_MASK ((BIT(5) - 1) << 27)
	#define USER1_BN_UC_DOUT_SHIFT 17
	#define USER1_BN_UC_DOUT_MASK (0xff << 16)
	#define USER1_BN_UC_DIN_SHIFT 8
	#define USER1_BN_UC_DIN_MASK (0xff << 8)
	#define USER4_CS_ACT BIT(30)
	#define SLAVE_TRST_DONE BIT(4)
	#define SLAVE_OP_MODE BIT(30)
	#define SLAVE_SW_RST BIT(31)

	#define SPIFC_BUFFER_SIZE 64

	/**
	* struct meson_spifc
	* @master: the SPI master
	* @regmap: regmap for device registers
	* @clk: input clock of the built-in baud rate generator
	* @dev: the device structure
	*/
	struct meson_spifc {
	struct spi_master *master;
	struct regmap *regmap;
	struct clk *clk;
	struct device *dev;
	};

	static const struct regmap_config spifc_regmap_config = {
	.reg_bits = 32,
	.val_bits = 32,
	.reg_stride = 4,
	.max_register = REG_MAX,
	};

	/**
	* meson_spifc_wait_ready() - wait for the current operation to terminate
	* @spifc: the Meson SPI device
	* Return: 0 on success, a negative value on error
	*/
	static int meson_spifc_wait_ready(struct meson_spifc *spifc)
	{
	unsigned long deadline = jiffies + msecs_to_jiffies(5);
	u32 data;

	do {
	regmap_read(spifc->regmap, REG_SLAVE, &data);
	if (data & SLAVE_TRST_DONE)
	return 0;
	cond_resched();
	} while (!time_after(jiffies, deadline));

	return -ETIMEDOUT;
	}

	/**
	* meson_spifc_drain_buffer() - copy data from device buffer to memory
	* @spifc: the Meson SPI device
	* @buf: the destination buffer
	* @len: number of bytes to copy
	*/
	static void meson_spifc_drain_buffer(struct meson_spifc spifc, u8 buf,
	int len)
	{
	u32 data;
	int i = 0;

	while (i < len) {
	regmap_read(spifc->regmap, REG_C0 + i, &data);

	if (len - i >= 4) {
	((u32 )buf) = data;
	buf += 4;
	} else {
	memcpy(buf, &data, len - i);
	break;
	}
	i += 4;
	}
	}

	/**
	* meson_spifc_fill_buffer() - copy data from memory to device buffer
	* @spifc: the Meson SPI device
	* @buf: the source buffer
	* @len: number of bytes to copy
	*/
	static void meson_spifc_fill_buffer(struct meson_spifc spifc, const u8 buf,
	int len)
	{
	u32 data;
	int i = 0;

	while (i < len) {
	if (len - i >= 4)
	data = (u32 )buf;
	else
	memcpy(&data, buf, len - i);

	regmap_write(spifc->regmap, REG_C0 + i, data);

	buf += 4;
	i += 4;
	}
	}

	/**
	* meson_spifc_setup_speed() - program the clock divider
	* @spifc: the Meson SPI device
	* @speed: desired speed in Hz
	*/
	static void meson_spifc_setup_speed(struct meson_spifc *spifc, u32 speed)
	{
	unsigned long parent, value;
	int n;

	parent = clk_get_rate(spifc->clk);
	n = max_t(int, parent / speed - 1, 1);

	dev_dbg(spifc->dev, "parent %lu, speed %u, n %d\n", parent,
	speed, n);

	value = (n << CLOCK_DIV_SHIFT) & CLOCK_DIV_MASK;
	value \|= (n << CLOCK_CNT_LOW_SHIFT) & CLOCK_CNT_LOW_MASK;
	value \|= (((n + 1) / 2 - 1) << CLOCK_CNT_HIGH_SHIFT) &
	CLOCK_CNT_HIGH_MASK;

	regmap_write(spifc->regmap, REG_CLOCK, value);
	}

	/**
	* meson_spifc_txrx() - transfer a chunk of data
	* @spifc: the Meson SPI device
	* @xfer: the current SPI transfer
	* @offset: offset of the data to transfer
	* @len: length of the data to transfer
	* @last_xfer: whether this is the last transfer of the message
	* @last_chunk: whether this is the last chunk of the transfer
	* Return: 0 on success, a negative value on error
	*/
	static int meson_spifc_txrx(struct meson_spifc *spifc,
	struct spi_transfer *xfer,
	int offset, int len, bool last_xfer,
	bool last_chunk)
	{
	bool keep_cs = true;
	int ret;

	if (xfer->tx_buf)
	meson_spifc_fill_buffer(spifc, xfer->tx_buf + offset, len);

	/* enable DOUT stage */
	regmap_update_bits(spifc->regmap, REG_USER, USER_UC_MASK,
	USER_UC_DOUT_SEL);
	regmap_write(spifc->regmap, REG_USER1,
	(8 * len - 1) << USER1_BN_UC_DOUT_SHIFT);

	/* enable data input during DOUT */
	regmap_update_bits(spifc->regmap, REG_USER, USER_DIN_EN_MS,
	USER_DIN_EN_MS);

	if (last_chunk) {
	if (last_xfer)
	keep_cs = xfer->cs_change;
	else
	keep_cs = !xfer->cs_change;
	}

	regmap_update_bits(spifc->regmap, REG_USER4, USER4_CS_ACT,
	keep_cs ? USER4_CS_ACT : 0);

	/* clear transition done bit */
	regmap_update_bits(spifc->regmap, REG_SLAVE, SLAVE_TRST_DONE, 0);
	/* start transfer */
	regmap_update_bits(spifc->regmap, REG_CMD, CMD_USER, CMD_USER);

	ret = meson_spifc_wait_ready(spifc);

	if (!ret && xfer->rx_buf)
	meson_spifc_drain_buffer(spifc, xfer->rx_buf + offset, len);

	return ret;
	}

	/**
	* meson_spifc_transfer_one() - perform a single transfer
	* @master: the SPI master
	* @spi: the SPI device
	* @xfer: the current SPI transfer
	* Return: 0 on success, a negative value on error
	*/
	static int meson_spifc_transfer_one(struct spi_master *master,
	struct spi_device *spi,
	struct spi_transfer *xfer)
	{
	struct meson_spifc *spifc = spi_master_get_devdata(master);
	int len, done = 0, ret = 0;

	meson_spifc_setup_speed(spifc, xfer->speed_hz);

	regmap_update_bits(spifc->regmap, REG_CTRL, CTRL_ENABLE_AHB, 0);

	while (done < xfer->len && !ret) {
	len = min_t(int, xfer->len - done, SPIFC_BUFFER_SIZE);
	ret = meson_spifc_txrx(spifc, xfer, done, len,
	spi_transfer_is_last(master, xfer),
	done + len >= xfer->len);
	done += len;
	}

	regmap_update_bits(spifc->regmap, REG_CTRL, CTRL_ENABLE_AHB,
	CTRL_ENABLE_AHB);

	return ret;
	}

	/**
	* meson_spifc_hw_init() - reset and initialize the SPI controller
	* @spifc: the Meson SPI device
	*/
	static void meson_spifc_hw_init(struct meson_spifc *spifc)
	{
	/* reset device */
	regmap_update_bits(spifc->regmap, REG_SLAVE, SLAVE_SW_RST,
	SLAVE_SW_RST);
	/* disable compatible mode */
	regmap_update_bits(spifc->regmap, REG_USER, USER_CMP_MODE, 0);
	/* set master mode */
	regmap_update_bits(spifc->regmap, REG_SLAVE, SLAVE_OP_MODE, 0);
	}

	static int meson_spifc_probe(struct platform_device *pdev)
	{
	struct spi_master *master;
	struct meson_spifc *spifc;
	void __iomem *base;
	unsigned int rate;
	int ret = 0;

	master = spi_alloc_master(&pdev->dev, sizeof(struct meson_spifc));
	if (!master)
	return -ENOMEM;

	platform_set_drvdata(pdev, master);

	spifc = spi_master_get_devdata(master);
	spifc->dev = &pdev->dev;

	base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(base)) {
	ret = PTR_ERR(base);
	goto out_err;
	}

	spifc->regmap = devm_regmap_init_mmio(spifc->dev, base,
	&spifc_regmap_config);
	if (IS_ERR(spifc->regmap)) {
	ret = PTR_ERR(spifc->regmap);
	goto out_err;
	}

	spifc->clk = devm_clk_get(spifc->dev, NULL);
	if (IS_ERR(spifc->clk)) {
	dev_err(spifc->dev, "missing clock\n");
	ret = PTR_ERR(spifc->clk);
	goto out_err;
	}

	ret = clk_prepare_enable(spifc->clk);
	if (ret) {
	dev_err(spifc->dev, "can't prepare clock\n");
	goto out_err;
	}

	rate = clk_get_rate(spifc->clk);

	master->num_chipselect = 1;
	master->dev.of_node = pdev->dev.of_node;
	master->bits_per_word_mask = SPI_BPW_MASK(8);
	master->auto_runtime_pm = true;
	master->transfer_one = meson_spifc_transfer_one;
	master->min_speed_hz = rate >> 6;
	master->max_speed_hz = rate >> 1;

	meson_spifc_hw_init(spifc);

	pm_runtime_set_active(spifc->dev);
	pm_runtime_enable(spifc->dev);

	ret = devm_spi_register_master(spifc->dev, master);
	if (ret) {
	dev_err(spifc->dev, "failed to register spi master\n");
	goto out_clk;
	}

	return 0;
	out_clk:
	clk_disable_unprepare(spifc->clk);
	pm_runtime_disable(spifc->dev);
	out_err:
	spi_master_put(master);
	return ret;
	}

	static int meson_spifc_remove(struct platform_device *pdev)
	{
	struct spi_master *master = platform_get_drvdata(pdev);
	struct meson_spifc *spifc = spi_master_get_devdata(master);

	pm_runtime_get_sync(&pdev->dev);
	clk_disable_unprepare(spifc->clk);
	pm_runtime_disable(&pdev->dev);

	return 0;
	}

	#ifdef CONFIG_PM_SLEEP
	static int meson_spifc_suspend(struct device *dev)
	{
	struct spi_master *master = dev_get_drvdata(dev);
	struct meson_spifc *spifc = spi_master_get_devdata(master);
	int ret;

	ret = spi_master_suspend(master);
	if (ret)
	return ret;

	if (!pm_runtime_suspended(dev))
	clk_disable_unprepare(spifc->clk);

	return 0;
	}

	static int meson_spifc_resume(struct device *dev)
	{
	struct spi_master *master = dev_get_drvdata(dev);
	struct meson_spifc *spifc = spi_master_get_devdata(master);
	int ret;

	if (!pm_runtime_suspended(dev)) {
	ret = clk_prepare_enable(spifc->clk);
	if (ret)
	return ret;
	}

	meson_spifc_hw_init(spifc);

	ret = spi_master_resume(master);
	if (ret)
	clk_disable_unprepare(spifc->clk);

	return ret;
	}
	#endif /* CONFIG_PM_SLEEP */

	#ifdef CONFIG_PM
	static int meson_spifc_runtime_suspend(struct device *dev)
	{
	struct spi_master *master = dev_get_drvdata(dev);
	struct meson_spifc *spifc = spi_master_get_devdata(master);

	clk_disable_unprepare(spifc->clk);

	return 0;
	}

	static int meson_spifc_runtime_resume(struct device *dev)
	{
	struct spi_master *master = dev_get_drvdata(dev);
	struct meson_spifc *spifc = spi_master_get_devdata(master);

	return clk_prepare_enable(spifc->clk);
	}
	#endif /* CONFIG_PM */

	static const struct dev_pm_ops meson_spifc_pm_ops = {
	SET_SYSTEM_SLEEP_PM_OPS(meson_spifc_suspend, meson_spifc_resume)
	SET_RUNTIME_PM_OPS(meson_spifc_runtime_suspend,
	meson_spifc_runtime_resume,
	NULL)
	};

	static const struct of_device_id meson_spifc_dt_match[] = {
	{ .compatible = "amlogic,meson6-spifc", },
	{ .compatible = "amlogic,meson-gxbb-spifc", },
	{ },
	};
	MODULE_DEVICE_TABLE(of, meson_spifc_dt_match);

	static struct platform_driver meson_spifc_driver = {
	.probe = meson_spifc_probe,
	.remove = meson_spifc_remove,
	.driver = {
	.name = "meson-spifc",
	.of_match_table = of_match_ptr(meson_spifc_dt_match),
	.pm = &meson_spifc_pm_ops,
	},
	};

	module_platform_driver(meson_spifc_driver);

	MODULE_AUTHOR("Beniamino Galvani <b.galvani@gmail.com>");
	MODULE_DESCRIPTION("Amlogic Meson SPIFC driver");
	MODULE_LICENSE("GPL v2");