/*
 *  R-Car Gen3 THS thermal sensor driver
 *  Based on rcar_thermal.c and work from Hien Dang and Khiem Nguyen.
 *
 * Copyright (C) 2016 Renesas Electronics Corporation.
 * Copyright (C) 2016 Sang Engineering
 *
 *  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; version 2 of the License.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 *
 */
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/thermal.h>

/* Register offsets */
#define REG_GEN3_IRQSTR		0x04
#define REG_GEN3_IRQMSK		0x08
#define REG_GEN3_IRQCTL		0x0C
#define REG_GEN3_IRQEN		0x10
#define REG_GEN3_IRQTEMP1	0x14
#define REG_GEN3_IRQTEMP2	0x18
#define REG_GEN3_IRQTEMP3	0x1C
#define REG_GEN3_CTSR		0x20
#define REG_GEN3_THCTR		0x20
#define REG_GEN3_TEMP		0x28
#define REG_GEN3_THCODE1	0x50
#define REG_GEN3_THCODE2	0x54
#define REG_GEN3_THCODE3	0x58

/* CTSR bits */
#define CTSR_PONM	BIT(8)
#define CTSR_AOUT	BIT(7)
#define CTSR_THBGR	BIT(5)
#define CTSR_VMEN	BIT(4)
#define CTSR_VMST	BIT(1)
#define CTSR_THSST	BIT(0)

/* THCTR bits */
#define THCTR_PONM	BIT(6)
#define THCTR_THSST	BIT(0)

#define CTEMP_MASK	0xFFF

#define MCELSIUS(temp)	((temp) * 1000)
#define GEN3_FUSE_MASK	0xFFF

#define TSC_MAX_NUM	3

/* Structure for thermal temperature calculation */
struct equation_coefs {
	int a1;
	int b1;
	int a2;
	int b2;
};

struct rcar_gen3_thermal_tsc {
	void __iomem *base;
	struct thermal_zone_device *zone;
	struct equation_coefs coef;
	struct mutex lock;
};

struct rcar_gen3_thermal_priv {
	struct rcar_gen3_thermal_tsc *tscs[TSC_MAX_NUM];
};

struct rcar_gen3_thermal_data {
	void (*thermal_init)(struct rcar_gen3_thermal_tsc *tsc);
};

static inline u32 rcar_gen3_thermal_read(struct rcar_gen3_thermal_tsc *tsc,
					 u32 reg)
{
	return ioread32(tsc->base + reg);
}

static inline void rcar_gen3_thermal_write(struct rcar_gen3_thermal_tsc *tsc,
					   u32 reg, u32 data)
{
	iowrite32(data, tsc->base + reg);
}

/*
 * Linear approximation for temperature
 *
 * [reg] = [temp] * a + b => [temp] = ([reg] - b) / a
 *
 * The constants a and b are calculated using two triplets of int values PTAT
 * and THCODE. PTAT and THCODE can either be read from hardware or use hard
 * coded values from driver. The formula to calculate a and b are taken from
 * BSP and sparsely documented and understood.
 *
 * Examining the linear formula and the formula used to calculate constants a
 * and b while knowing that the span for PTAT and THCODE values are between
 * 0x000 and 0xfff the largest integer possible is 0xfff * 0xfff == 0xffe001.
 * Integer also needs to be signed so that leaves 7 bits for binary
 * fixed point scaling.
 */

#define FIXPT_SHIFT 7
#define FIXPT_INT(_x) ((_x) << FIXPT_SHIFT)
#define FIXPT_DIV(_a, _b) DIV_ROUND_CLOSEST(((_a) << FIXPT_SHIFT), (_b))
#define FIXPT_TO_MCELSIUS(_x) ((_x) * 1000 >> FIXPT_SHIFT)

#define RCAR3_THERMAL_GRAN 500 /* mili Celsius */

/* no idea where these constants come from */
#define TJ_1 96
#define TJ_3 -41

static void rcar_gen3_thermal_calc_coefs(struct equation_coefs *coef,
					 int *ptat, int *thcode)
{
	int tj_2;

	/* TODO: Find documentation and document constant calculation formula */

	/*
	 * Division is not scaled in BSP and if scaled it might overflow
	 * the dividend (4095 * 4095 << 14 > INT_MAX) so keep it unscaled
	 */
	tj_2 = (FIXPT_INT((ptat[1] - ptat[2]) * 137)
		/ (ptat[0] - ptat[2])) - FIXPT_INT(41);

	coef->a1 = FIXPT_DIV(FIXPT_INT(thcode[1] - thcode[2]),
			     tj_2 - FIXPT_INT(TJ_3));
	coef->b1 = FIXPT_INT(thcode[2]) - coef->a1 * TJ_3;

	coef->a2 = FIXPT_DIV(FIXPT_INT(thcode[1] - thcode[0]),
			     tj_2 - FIXPT_INT(TJ_1));
	coef->b2 = FIXPT_INT(thcode[0]) - coef->a2 * TJ_1;
}

static int rcar_gen3_thermal_round(int temp)
{
	int result, round_offs;

	round_offs = temp >= 0 ? RCAR3_THERMAL_GRAN / 2 :
		-RCAR3_THERMAL_GRAN / 2;
	result = (temp + round_offs) / RCAR3_THERMAL_GRAN;
	return result * RCAR3_THERMAL_GRAN;
}

static int rcar_gen3_thermal_get_temp(void *devdata, int *temp)
{
	struct rcar_gen3_thermal_tsc *tsc = devdata;
	int mcelsius, val1, val2;
	u32 reg;

	/* Read register and convert to mili Celsius */
	mutex_lock(&tsc->lock);

	reg = rcar_gen3_thermal_read(tsc, REG_GEN3_TEMP) & CTEMP_MASK;

	val1 = FIXPT_DIV(FIXPT_INT(reg) - tsc->coef.b1, tsc->coef.a1);
	val2 = FIXPT_DIV(FIXPT_INT(reg) - tsc->coef.b2, tsc->coef.a2);
	mcelsius = FIXPT_TO_MCELSIUS((val1 + val2) / 2);

	mutex_unlock(&tsc->lock);

	/* Make sure we are inside specifications */
	if ((mcelsius < MCELSIUS(-40)) || (mcelsius > MCELSIUS(125)))
		return -EIO;

	/* Round value to device granularity setting */
	*temp = rcar_gen3_thermal_round(mcelsius);

	return 0;
}

static struct thermal_zone_of_device_ops rcar_gen3_tz_of_ops = {
	.get_temp	= rcar_gen3_thermal_get_temp,
};

static void r8a7795_thermal_init(struct rcar_gen3_thermal_tsc *tsc)
{
	rcar_gen3_thermal_write(tsc, REG_GEN3_CTSR,  CTSR_THBGR);
	rcar_gen3_thermal_write(tsc, REG_GEN3_CTSR,  0x0);

	usleep_range(1000, 2000);

	rcar_gen3_thermal_write(tsc, REG_GEN3_CTSR, CTSR_PONM);
	rcar_gen3_thermal_write(tsc, REG_GEN3_IRQCTL, 0x3F);
	rcar_gen3_thermal_write(tsc, REG_GEN3_CTSR,
				CTSR_PONM | CTSR_AOUT | CTSR_THBGR | CTSR_VMEN);

	usleep_range(100, 200);

	rcar_gen3_thermal_write(tsc, REG_GEN3_CTSR,
				CTSR_PONM | CTSR_AOUT | CTSR_THBGR | CTSR_VMEN |
				CTSR_VMST | CTSR_THSST);

	usleep_range(1000, 2000);
}

static void r8a7796_thermal_init(struct rcar_gen3_thermal_tsc *tsc)
{
	u32 reg_val;

	reg_val = rcar_gen3_thermal_read(tsc, REG_GEN3_THCTR);
	reg_val &= ~THCTR_PONM;
	rcar_gen3_thermal_write(tsc, REG_GEN3_THCTR, reg_val);

	usleep_range(1000, 2000);

	rcar_gen3_thermal_write(tsc, REG_GEN3_IRQCTL, 0x3F);
	reg_val = rcar_gen3_thermal_read(tsc, REG_GEN3_THCTR);
	reg_val |= THCTR_THSST;
	rcar_gen3_thermal_write(tsc, REG_GEN3_THCTR, reg_val);
}

static const struct rcar_gen3_thermal_data r8a7795_data = {
	.thermal_init = r8a7795_thermal_init,
};

static const struct rcar_gen3_thermal_data r8a7796_data = {
	.thermal_init = r8a7796_thermal_init,
};

static const struct of_device_id rcar_gen3_thermal_dt_ids[] = {
	{ .compatible = "renesas,r8a7795-thermal", .data = &r8a7795_data},
	{ .compatible = "renesas,r8a7796-thermal", .data = &r8a7796_data},
	{},
};
MODULE_DEVICE_TABLE(of, rcar_gen3_thermal_dt_ids);

static int rcar_gen3_thermal_remove(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;

	pm_runtime_put(dev);
	pm_runtime_disable(dev);

	return 0;
}

static int rcar_gen3_thermal_probe(struct platform_device *pdev)
{
	struct rcar_gen3_thermal_priv *priv;
	struct device *dev = &pdev->dev;
	struct resource *res;
	struct thermal_zone_device *zone;
	int ret, i;
	const struct rcar_gen3_thermal_data *match_data =
		of_device_get_match_data(dev);

	/* default values if FUSEs are missing */
	/* TODO: Read values from hardware on supported platforms */
	int ptat[3] = { 2351, 1509, 435 };
	int thcode[TSC_MAX_NUM][3] = {
		{ 3248, 2800, 2221 },
		{ 3245, 2795, 2216 },
		{ 3250, 2805, 2237 },
	};

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	platform_set_drvdata(pdev, priv);

	pm_runtime_enable(dev);
	pm_runtime_get_sync(dev);

	for (i = 0; i < TSC_MAX_NUM; i++) {
		struct rcar_gen3_thermal_tsc *tsc;

		tsc = devm_kzalloc(dev, sizeof(*tsc), GFP_KERNEL);
		if (!tsc) {
			ret = -ENOMEM;
			goto error_unregister;
		}

		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
		if (!res)
			break;

		tsc->base = devm_ioremap_resource(dev, res);
		if (IS_ERR(tsc->base)) {
			ret = PTR_ERR(tsc->base);
			goto error_unregister;
		}

		priv->tscs[i] = tsc;
		mutex_init(&tsc->lock);

		match_data->thermal_init(tsc);
		rcar_gen3_thermal_calc_coefs(&tsc->coef, ptat, thcode[i]);

		zone = devm_thermal_zone_of_sensor_register(dev, i, tsc,
							    &rcar_gen3_tz_of_ops);
		if (IS_ERR(zone)) {
			dev_err(dev, "Can't register thermal zone\n");
			ret = PTR_ERR(zone);
			goto error_unregister;
		}
		tsc->zone = zone;
	}

	return 0;

error_unregister:
	rcar_gen3_thermal_remove(pdev);

	return ret;
}

static struct platform_driver rcar_gen3_thermal_driver = {
	.driver	= {
		.name	= "rcar_gen3_thermal",
		.of_match_table = rcar_gen3_thermal_dt_ids,
	},
	.probe		= rcar_gen3_thermal_probe,
	.remove		= rcar_gen3_thermal_remove,
};
module_platform_driver(rcar_gen3_thermal_driver);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("R-Car Gen3 THS thermal sensor driver");
MODULE_AUTHOR("Wolfram Sang <wsa+renesas@sang-engineering.com>");