/*
 * P2WI (Push-Pull Two Wire Interface) bus driver.
 *
 * Author: Boris BREZILLON <boris.brezillon@free-electrons.com>
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2.  This program is licensed "as is" without any warranty of any
 * kind, whether express or implied.
 *
 * The P2WI controller looks like an SMBus controller which only supports byte
 * data transfers. But, it differs from standard SMBus protocol on several
 * aspects:
 * - it supports only one slave device, and thus drop the address field
 * - it adds a parity bit every 8bits of data
 * - only one read access is required to read a byte (instead of a write
 *   followed by a read access in standard SMBus protocol)
 * - there's no Ack bit after each byte transfer
 *
 * This means this bus cannot be used to interface with standard SMBus
 * devices (the only known device to support this interface is the AXP221
 * PMIC).
 *
 */
#include <linux/clk.h>
#include <linux/i2c.h>
#include <linux/io.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/reset.h>


/* P2WI registers */
#define P2WI_CTRL		0x0
#define P2WI_CCR		0x4
#define P2WI_INTE		0x8
#define P2WI_INTS		0xc
#define P2WI_DADDR0		0x10
#define P2WI_DADDR1		0x14
#define P2WI_DLEN		0x18
#define P2WI_DATA0		0x1c
#define P2WI_DATA1		0x20
#define P2WI_LCR		0x24
#define P2WI_PMCR		0x28

/* CTRL fields */
#define P2WI_CTRL_START_TRANS		BIT(7)
#define P2WI_CTRL_ABORT_TRANS		BIT(6)
#define P2WI_CTRL_GLOBAL_INT_ENB	BIT(1)
#define P2WI_CTRL_SOFT_RST		BIT(0)

/* CLK CTRL fields */
#define P2WI_CCR_SDA_OUT_DELAY(v)	(((v) & 0x7) << 8)
#define P2WI_CCR_MAX_CLK_DIV		0xff
#define P2WI_CCR_CLK_DIV(v)		((v) & P2WI_CCR_MAX_CLK_DIV)

/* STATUS fields */
#define P2WI_INTS_TRANS_ERR_ID(v)	(((v) >> 8) & 0xff)
#define P2WI_INTS_LOAD_BSY		BIT(2)
#define P2WI_INTS_TRANS_ERR		BIT(1)
#define P2WI_INTS_TRANS_OVER		BIT(0)

/* DATA LENGTH fields*/
#define P2WI_DLEN_READ			BIT(4)
#define P2WI_DLEN_DATA_LENGTH(v)	((v - 1) & 0x7)

/* LINE CTRL fields*/
#define P2WI_LCR_SCL_STATE		BIT(5)
#define P2WI_LCR_SDA_STATE		BIT(4)
#define P2WI_LCR_SCL_CTL		BIT(3)
#define P2WI_LCR_SCL_CTL_EN		BIT(2)
#define P2WI_LCR_SDA_CTL		BIT(1)
#define P2WI_LCR_SDA_CTL_EN		BIT(0)

/* PMU MODE CTRL fields */
#define P2WI_PMCR_PMU_INIT_SEND		BIT(31)
#define P2WI_PMCR_PMU_INIT_DATA(v)	(((v) & 0xff) << 16)
#define P2WI_PMCR_PMU_MODE_REG(v)	(((v) & 0xff) << 8)
#define P2WI_PMCR_PMU_DEV_ADDR(v)	((v) & 0xff)

#define P2WI_MAX_FREQ			6000000

struct p2wi {
	struct i2c_adapter adapter;
	struct completion complete;
	unsigned int status;
	void __iomem *regs;
	struct clk *clk;
	struct reset_control *rstc;
	int slave_addr;
};

static irqreturn_t p2wi_interrupt(int irq, void *dev_id)
{
	struct p2wi *p2wi = dev_id;
	unsigned long status;

	status = readl(p2wi->regs + P2WI_INTS);
	p2wi->status = status;

	/* Clear interrupts */
	status &= (P2WI_INTS_LOAD_BSY | P2WI_INTS_TRANS_ERR |
		   P2WI_INTS_TRANS_OVER);
	writel(status, p2wi->regs + P2WI_INTS);

	complete(&p2wi->complete);

	return IRQ_HANDLED;
}

static u32 p2wi_functionality(struct i2c_adapter *adap)
{
	return I2C_FUNC_SMBUS_BYTE_DATA;
}

static int p2wi_smbus_xfer(struct i2c_adapter *adap, u16 addr,
			   unsigned short flags, char read_write,
			   u8 command, int size, union i2c_smbus_data *data)
{
	struct p2wi *p2wi = i2c_get_adapdata(adap);
	unsigned long dlen = P2WI_DLEN_DATA_LENGTH(1);

	if (p2wi->slave_addr >= 0 && addr != p2wi->slave_addr) {
		dev_err(&adap->dev, "invalid P2WI address\n");
		return -EINVAL;
	}

	if (!data)
		return -EINVAL;

	writel(command, p2wi->regs + P2WI_DADDR0);

	if (read_write == I2C_SMBUS_READ)
		dlen |= P2WI_DLEN_READ;
	else
		writel(data->byte, p2wi->regs + P2WI_DATA0);

	writel(dlen, p2wi->regs + P2WI_DLEN);

	if (readl(p2wi->regs + P2WI_CTRL) & P2WI_CTRL_START_TRANS) {
		dev_err(&adap->dev, "P2WI bus busy\n");
		return -EBUSY;
	}

	reinit_completion(&p2wi->complete);

	writel(P2WI_INTS_LOAD_BSY | P2WI_INTS_TRANS_ERR | P2WI_INTS_TRANS_OVER,
	       p2wi->regs + P2WI_INTE);

	writel(P2WI_CTRL_START_TRANS | P2WI_CTRL_GLOBAL_INT_ENB,
	       p2wi->regs + P2WI_CTRL);

	wait_for_completion(&p2wi->complete);

	if (p2wi->status & P2WI_INTS_LOAD_BSY) {
		dev_err(&adap->dev, "P2WI bus busy\n");
		return -EBUSY;
	}

	if (p2wi->status & P2WI_INTS_TRANS_ERR) {
		dev_err(&adap->dev, "P2WI bus xfer error\n");
		return -ENXIO;
	}

	if (read_write == I2C_SMBUS_READ)
		data->byte = readl(p2wi->regs + P2WI_DATA0);

	return 0;
}

static const struct i2c_algorithm p2wi_algo = {
	.smbus_xfer = p2wi_smbus_xfer,
	.functionality = p2wi_functionality,
};

static const struct of_device_id p2wi_of_match_table[] = {
	{ .compatible = "allwinner,sun6i-a31-p2wi" },
	{}
};
MODULE_DEVICE_TABLE(of, p2wi_of_match_table);

static int p2wi_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct device_node *np = dev->of_node;
	struct device_node *childnp;
	unsigned long parent_clk_freq;
	u32 clk_freq = I2C_MAX_STANDARD_MODE_FREQ;
	struct p2wi *p2wi;
	u32 slave_addr;
	int clk_div;
	int irq;
	int ret;

	of_property_read_u32(np, "clock-frequency", &clk_freq);
	if (clk_freq > P2WI_MAX_FREQ) {
		dev_err(dev,
			"required clock-frequency (%u Hz) is too high (max = 6MHz)",
			clk_freq);
		return -EINVAL;
	}

	if (of_get_child_count(np) > 1) {
		dev_err(dev, "P2WI only supports one slave device\n");
		return -EINVAL;
	}

	p2wi = devm_kzalloc(dev, sizeof(struct p2wi), GFP_KERNEL);
	if (!p2wi)
		return -ENOMEM;

	p2wi->slave_addr = -1;

	/*
	 * Authorize a p2wi node without any children to be able to use an
	 * i2c-dev from userpace.
	 * In this case the slave_addr is set to -1 and won't be checked when
	 * launching a P2WI transfer.
	 */
	childnp = of_get_next_available_child(np, NULL);
	if (childnp) {
		ret = of_property_read_u32(childnp, "reg", &slave_addr);
		if (ret) {
			dev_err(dev, "invalid slave address on node %pOF\n",
				childnp);
			return -EINVAL;
		}

		p2wi->slave_addr = slave_addr;
	}

	p2wi->regs = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(p2wi->regs))
		return PTR_ERR(p2wi->regs);

	strscpy(p2wi->adapter.name, pdev->name, sizeof(p2wi->adapter.name));
	irq = platform_get_irq(pdev, 0);
	if (irq < 0)
		return irq;

	p2wi->clk = devm_clk_get(dev, NULL);
	if (IS_ERR(p2wi->clk)) {
		ret = PTR_ERR(p2wi->clk);
		dev_err(dev, "failed to retrieve clk: %d\n", ret);
		return ret;
	}

	ret = clk_prepare_enable(p2wi->clk);
	if (ret) {
		dev_err(dev, "failed to enable clk: %d\n", ret);
		return ret;
	}

	parent_clk_freq = clk_get_rate(p2wi->clk);

	p2wi->rstc = devm_reset_control_get_exclusive(dev, NULL);
	if (IS_ERR(p2wi->rstc)) {
		ret = PTR_ERR(p2wi->rstc);
		dev_err(dev, "failed to retrieve reset controller: %d\n", ret);
		goto err_clk_disable;
	}

	ret = reset_control_deassert(p2wi->rstc);
	if (ret) {
		dev_err(dev, "failed to deassert reset line: %d\n", ret);
		goto err_clk_disable;
	}

	init_completion(&p2wi->complete);
	p2wi->adapter.dev.parent = dev;
	p2wi->adapter.algo = &p2wi_algo;
	p2wi->adapter.owner = THIS_MODULE;
	p2wi->adapter.dev.of_node = pdev->dev.of_node;
	platform_set_drvdata(pdev, p2wi);
	i2c_set_adapdata(&p2wi->adapter, p2wi);

	ret = devm_request_irq(dev, irq, p2wi_interrupt, 0, pdev->name, p2wi);
	if (ret) {
		dev_err(dev, "can't register interrupt handler irq%d: %d\n",
			irq, ret);
		goto err_reset_assert;
	}

	writel(P2WI_CTRL_SOFT_RST, p2wi->regs + P2WI_CTRL);

	clk_div = parent_clk_freq / clk_freq;
	if (!clk_div) {
		dev_warn(dev,
			 "clock-frequency is too high, setting it to %lu Hz\n",
			 parent_clk_freq);
		clk_div = 1;
	} else if (clk_div > P2WI_CCR_MAX_CLK_DIV) {
		dev_warn(dev,
			 "clock-frequency is too low, setting it to %lu Hz\n",
			 parent_clk_freq / P2WI_CCR_MAX_CLK_DIV);
		clk_div = P2WI_CCR_MAX_CLK_DIV;
	}

	writel(P2WI_CCR_SDA_OUT_DELAY(1) | P2WI_CCR_CLK_DIV(clk_div),
	       p2wi->regs + P2WI_CCR);

	ret = i2c_add_adapter(&p2wi->adapter);
	if (!ret)
		return 0;

err_reset_assert:
	reset_control_assert(p2wi->rstc);

err_clk_disable:
	clk_disable_unprepare(p2wi->clk);

	return ret;
}

static int p2wi_remove(struct platform_device *dev)
{
	struct p2wi *p2wi = platform_get_drvdata(dev);

	reset_control_assert(p2wi->rstc);
	clk_disable_unprepare(p2wi->clk);
	i2c_del_adapter(&p2wi->adapter);

	return 0;
}

static struct platform_driver p2wi_driver = {
	.probe	= p2wi_probe,
	.remove	= p2wi_remove,
	.driver	= {
		.name = "i2c-sunxi-p2wi",
		.of_match_table = p2wi_of_match_table,
	},
};
module_platform_driver(p2wi_driver);

MODULE_AUTHOR("Boris BREZILLON <boris.brezillon@free-electrons.com>");
MODULE_DESCRIPTION("Allwinner P2WI driver");
MODULE_LICENSE("GPL v2");