/*
 * Driver for Amlogic Meson SPI flash controller (SPIFC)
 *
 * Copyright (C) 2014 Beniamino Galvani <b.galvani@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#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
 * @device:	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;
	struct resource *res;
	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;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	base = devm_ioremap_resource(spifc->dev, res);
	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);
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");