/*
 * RTC Driver for X-Powers AC100
 *
 * Copyright (c) 2016 Chen-Yu Tsai
 *
 * Chen-Yu Tsai <wens@csie.org>
 *
 * 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.
 *
 * 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/bcd.h>
#include <linux/clk-provider.h>
#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/mfd/ac100.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/rtc.h>
#include <linux/types.h>

/* Control register */
#define AC100_RTC_CTRL_24HOUR	BIT(0)

/* Clock output register bits */
#define AC100_CLKOUT_PRE_DIV_SHIFT	5
#define AC100_CLKOUT_PRE_DIV_WIDTH	3
#define AC100_CLKOUT_MUX_SHIFT		4
#define AC100_CLKOUT_MUX_WIDTH		1
#define AC100_CLKOUT_DIV_SHIFT		1
#define AC100_CLKOUT_DIV_WIDTH		3
#define AC100_CLKOUT_EN			BIT(0)

/* RTC */
#define AC100_RTC_SEC_MASK	GENMASK(6, 0)
#define AC100_RTC_MIN_MASK	GENMASK(6, 0)
#define AC100_RTC_HOU_MASK	GENMASK(5, 0)
#define AC100_RTC_WEE_MASK	GENMASK(2, 0)
#define AC100_RTC_DAY_MASK	GENMASK(5, 0)
#define AC100_RTC_MON_MASK	GENMASK(4, 0)
#define AC100_RTC_YEA_MASK	GENMASK(7, 0)
#define AC100_RTC_YEA_LEAP	BIT(15)
#define AC100_RTC_UPD_TRIGGER	BIT(15)

/* Alarm (wall clock) */
#define AC100_ALM_INT_ENABLE	BIT(0)

#define AC100_ALM_SEC_MASK	GENMASK(6, 0)
#define AC100_ALM_MIN_MASK	GENMASK(6, 0)
#define AC100_ALM_HOU_MASK	GENMASK(5, 0)
#define AC100_ALM_WEE_MASK	GENMASK(2, 0)
#define AC100_ALM_DAY_MASK	GENMASK(5, 0)
#define AC100_ALM_MON_MASK	GENMASK(4, 0)
#define AC100_ALM_YEA_MASK	GENMASK(7, 0)
#define AC100_ALM_ENABLE_FLAG	BIT(15)
#define AC100_ALM_UPD_TRIGGER	BIT(15)

/*
 * The year parameter passed to the driver is usually an offset relative to
 * the year 1900. This macro is used to convert this offset to another one
 * relative to the minimum year allowed by the hardware.
 *
 * The year range is 1970 - 2069. This range is selected to match Allwinner's
 * driver.
 */
#define AC100_YEAR_MIN				1970
#define AC100_YEAR_MAX				2069
#define AC100_YEAR_OFF				(AC100_YEAR_MIN - 1900)

struct ac100_clkout {
	struct clk_hw hw;
	struct regmap *regmap;
	u8 offset;
};

#define to_ac100_clkout(_hw) container_of(_hw, struct ac100_clkout, hw)

#define AC100_RTC_32K_NAME	"ac100-rtc-32k"
#define AC100_RTC_32K_RATE	32768
#define AC100_CLKOUT_NUM	3

static const char * const ac100_clkout_names[AC100_CLKOUT_NUM] = {
	"ac100-cko1-rtc",
	"ac100-cko2-rtc",
	"ac100-cko3-rtc",
};

struct ac100_rtc_dev {
	struct rtc_device *rtc;
	struct device *dev;
	struct regmap *regmap;
	int irq;
	unsigned long alarm;

	struct clk_hw *rtc_32k_clk;
	struct ac100_clkout clks[AC100_CLKOUT_NUM];
	struct clk_hw_onecell_data *clk_data;
};

/**
 * Clock controls for 3 clock output pins
 */

static const struct clk_div_table ac100_clkout_prediv[] = {
	{ .val = 0, .div = 1 },
	{ .val = 1, .div = 2 },
	{ .val = 2, .div = 4 },
	{ .val = 3, .div = 8 },
	{ .val = 4, .div = 16 },
	{ .val = 5, .div = 32 },
	{ .val = 6, .div = 64 },
	{ .val = 7, .div = 122 },
	{ },
};

/* Abuse the fact that one parent is 32768 Hz, and the other is 4 MHz */
static unsigned long ac100_clkout_recalc_rate(struct clk_hw *hw,
					      unsigned long prate)
{
	struct ac100_clkout *clk = to_ac100_clkout(hw);
	unsigned int reg, div;

	regmap_read(clk->regmap, clk->offset, &reg);

	/* Handle pre-divider first */
	if (prate != AC100_RTC_32K_RATE) {
		div = (reg >> AC100_CLKOUT_PRE_DIV_SHIFT) &
			((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1);
		prate = divider_recalc_rate(hw, prate, div,
					    ac100_clkout_prediv, 0,
					    AC100_CLKOUT_PRE_DIV_WIDTH);
	}

	div = (reg >> AC100_CLKOUT_DIV_SHIFT) &
		(BIT(AC100_CLKOUT_DIV_WIDTH) - 1);
	return divider_recalc_rate(hw, prate, div, NULL,
				   CLK_DIVIDER_POWER_OF_TWO,
				   AC100_CLKOUT_DIV_WIDTH);
}

static long ac100_clkout_round_rate(struct clk_hw *hw, unsigned long rate,
				    unsigned long prate)
{
	unsigned long best_rate = 0, tmp_rate, tmp_prate;
	int i;

	if (prate == AC100_RTC_32K_RATE)
		return divider_round_rate(hw, rate, &prate, NULL,
					  AC100_CLKOUT_DIV_WIDTH,
					  CLK_DIVIDER_POWER_OF_TWO);

	for (i = 0; ac100_clkout_prediv[i].div; i++) {
		tmp_prate = DIV_ROUND_UP(prate, ac100_clkout_prediv[i].val);
		tmp_rate = divider_round_rate(hw, rate, &tmp_prate, NULL,
					      AC100_CLKOUT_DIV_WIDTH,
					      CLK_DIVIDER_POWER_OF_TWO);

		if (tmp_rate > rate)
			continue;
		if (rate - tmp_rate < best_rate - tmp_rate)
			best_rate = tmp_rate;
	}

	return best_rate;
}

static int ac100_clkout_determine_rate(struct clk_hw *hw,
				       struct clk_rate_request *req)
{
	struct clk_hw *best_parent;
	unsigned long best = 0;
	int i, num_parents = clk_hw_get_num_parents(hw);

	for (i = 0; i < num_parents; i++) {
		struct clk_hw *parent = clk_hw_get_parent_by_index(hw, i);
		unsigned long tmp, prate = clk_hw_get_rate(parent);

		tmp = ac100_clkout_round_rate(hw, req->rate, prate);

		if (tmp > req->rate)
			continue;
		if (req->rate - tmp < req->rate - best) {
			best = tmp;
			best_parent = parent;
		}
	}

	if (!best)
		return -EINVAL;

	req->best_parent_hw = best_parent;
	req->best_parent_rate = best;
	req->rate = best;

	return 0;
}

static int ac100_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
				 unsigned long prate)
{
	struct ac100_clkout *clk = to_ac100_clkout(hw);
	int div = 0, pre_div = 0;

	do {
		div = divider_get_val(rate * ac100_clkout_prediv[pre_div].div,
				      prate, NULL, AC100_CLKOUT_DIV_WIDTH,
				      CLK_DIVIDER_POWER_OF_TWO);
		if (div >= 0)
			break;
	} while (prate != AC100_RTC_32K_RATE &&
		 ac100_clkout_prediv[++pre_div].div);

	if (div < 0)
		return div;

	pre_div = ac100_clkout_prediv[pre_div].val;

	regmap_update_bits(clk->regmap, clk->offset,
			   ((1 << AC100_CLKOUT_DIV_WIDTH) - 1) << AC100_CLKOUT_DIV_SHIFT |
			   ((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1) << AC100_CLKOUT_PRE_DIV_SHIFT,
			   (div - 1) << AC100_CLKOUT_DIV_SHIFT |
			   (pre_div - 1) << AC100_CLKOUT_PRE_DIV_SHIFT);

	return 0;
}

static int ac100_clkout_prepare(struct clk_hw *hw)
{
	struct ac100_clkout *clk = to_ac100_clkout(hw);

	return regmap_update_bits(clk->regmap, clk->offset, AC100_CLKOUT_EN,
				  AC100_CLKOUT_EN);
}

static void ac100_clkout_unprepare(struct clk_hw *hw)
{
	struct ac100_clkout *clk = to_ac100_clkout(hw);

	regmap_update_bits(clk->regmap, clk->offset, AC100_CLKOUT_EN, 0);
}

static int ac100_clkout_is_prepared(struct clk_hw *hw)
{
	struct ac100_clkout *clk = to_ac100_clkout(hw);
	unsigned int reg;

	regmap_read(clk->regmap, clk->offset, &reg);

	return reg & AC100_CLKOUT_EN;
}

static u8 ac100_clkout_get_parent(struct clk_hw *hw)
{
	struct ac100_clkout *clk = to_ac100_clkout(hw);
	unsigned int reg;

	regmap_read(clk->regmap, clk->offset, &reg);

	return (reg >> AC100_CLKOUT_MUX_SHIFT) & 0x1;
}

static int ac100_clkout_set_parent(struct clk_hw *hw, u8 index)
{
	struct ac100_clkout *clk = to_ac100_clkout(hw);

	return regmap_update_bits(clk->regmap, clk->offset,
				  BIT(AC100_CLKOUT_MUX_SHIFT),
				  index ? BIT(AC100_CLKOUT_MUX_SHIFT) : 0);
}

static const struct clk_ops ac100_clkout_ops = {
	.prepare	= ac100_clkout_prepare,
	.unprepare	= ac100_clkout_unprepare,
	.is_prepared	= ac100_clkout_is_prepared,
	.recalc_rate	= ac100_clkout_recalc_rate,
	.determine_rate	= ac100_clkout_determine_rate,
	.get_parent	= ac100_clkout_get_parent,
	.set_parent	= ac100_clkout_set_parent,
	.set_rate	= ac100_clkout_set_rate,
};

static int ac100_rtc_register_clks(struct ac100_rtc_dev *chip)
{
	struct device_node *np = chip->dev->of_node;
	const char *parents[2] = {AC100_RTC_32K_NAME};
	int i, ret;

	chip->clk_data = devm_kzalloc(chip->dev,
				      struct_size(chip->clk_data, hws,
						  AC100_CLKOUT_NUM),
				      GFP_KERNEL);
	if (!chip->clk_data)
		return -ENOMEM;

	chip->rtc_32k_clk = clk_hw_register_fixed_rate(chip->dev,
						       AC100_RTC_32K_NAME,
						       NULL, 0,
						       AC100_RTC_32K_RATE);
	if (IS_ERR(chip->rtc_32k_clk)) {
		ret = PTR_ERR(chip->rtc_32k_clk);
		dev_err(chip->dev, "Failed to register RTC-32k clock: %d\n",
			ret);
		return ret;
	}

	parents[1] = of_clk_get_parent_name(np, 0);
	if (!parents[1]) {
		dev_err(chip->dev, "Failed to get ADDA 4M clock\n");
		return -EINVAL;
	}

	for (i = 0; i < AC100_CLKOUT_NUM; i++) {
		struct ac100_clkout *clk = &chip->clks[i];
		struct clk_init_data init = {
			.name = ac100_clkout_names[i],
			.ops = &ac100_clkout_ops,
			.parent_names = parents,
			.num_parents = ARRAY_SIZE(parents),
			.flags = 0,
		};

		of_property_read_string_index(np, "clock-output-names",
					      i, &init.name);
		clk->regmap = chip->regmap;
		clk->offset = AC100_CLKOUT_CTRL1 + i;
		clk->hw.init = &init;

		ret = devm_clk_hw_register(chip->dev, &clk->hw);
		if (ret) {
			dev_err(chip->dev, "Failed to register clk '%s': %d\n",
				init.name, ret);
			goto err_unregister_rtc_32k;
		}

		chip->clk_data->hws[i] = &clk->hw;
	}

	chip->clk_data->num = i;
	ret = of_clk_add_hw_provider(np, of_clk_hw_onecell_get, chip->clk_data);
	if (ret)
		goto err_unregister_rtc_32k;

	return 0;

err_unregister_rtc_32k:
	clk_unregister_fixed_rate(chip->rtc_32k_clk->clk);

	return ret;
}

static void ac100_rtc_unregister_clks(struct ac100_rtc_dev *chip)
{
	of_clk_del_provider(chip->dev->of_node);
	clk_unregister_fixed_rate(chip->rtc_32k_clk->clk);
}

/**
 * RTC related bits
 */
static int ac100_rtc_get_time(struct device *dev, struct rtc_time *rtc_tm)
{
	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
	struct regmap *regmap = chip->regmap;
	u16 reg[7];
	int ret;

	ret = regmap_bulk_read(regmap, AC100_RTC_SEC, reg, 7);
	if (ret)
		return ret;

	rtc_tm->tm_sec  = bcd2bin(reg[0] & AC100_RTC_SEC_MASK);
	rtc_tm->tm_min  = bcd2bin(reg[1] & AC100_RTC_MIN_MASK);
	rtc_tm->tm_hour = bcd2bin(reg[2] & AC100_RTC_HOU_MASK);
	rtc_tm->tm_wday = bcd2bin(reg[3] & AC100_RTC_WEE_MASK);
	rtc_tm->tm_mday = bcd2bin(reg[4] & AC100_RTC_DAY_MASK);
	rtc_tm->tm_mon  = bcd2bin(reg[5] & AC100_RTC_MON_MASK) - 1;
	rtc_tm->tm_year = bcd2bin(reg[6] & AC100_RTC_YEA_MASK) +
			  AC100_YEAR_OFF;

	return rtc_valid_tm(rtc_tm);
}

static int ac100_rtc_set_time(struct device *dev, struct rtc_time *rtc_tm)
{
	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
	struct regmap *regmap = chip->regmap;
	int year;
	u16 reg[8];

	/* our RTC has a limited year range... */
	year = rtc_tm->tm_year - AC100_YEAR_OFF;
	if (year < 0 || year > (AC100_YEAR_MAX - 1900)) {
		dev_err(dev, "rtc only supports year in range %d - %d\n",
			AC100_YEAR_MIN, AC100_YEAR_MAX);
		return -EINVAL;
	}

	/* convert to BCD */
	reg[0] = bin2bcd(rtc_tm->tm_sec)     & AC100_RTC_SEC_MASK;
	reg[1] = bin2bcd(rtc_tm->tm_min)     & AC100_RTC_MIN_MASK;
	reg[2] = bin2bcd(rtc_tm->tm_hour)    & AC100_RTC_HOU_MASK;
	reg[3] = bin2bcd(rtc_tm->tm_wday)    & AC100_RTC_WEE_MASK;
	reg[4] = bin2bcd(rtc_tm->tm_mday)    & AC100_RTC_DAY_MASK;
	reg[5] = bin2bcd(rtc_tm->tm_mon + 1) & AC100_RTC_MON_MASK;
	reg[6] = bin2bcd(year)		     & AC100_RTC_YEA_MASK;
	/* trigger write */
	reg[7] = AC100_RTC_UPD_TRIGGER;

	/* Is it a leap year? */
	if (is_leap_year(year + AC100_YEAR_OFF + 1900))
		reg[6] |= AC100_RTC_YEA_LEAP;

	return regmap_bulk_write(regmap, AC100_RTC_SEC, reg, 8);
}

static int ac100_rtc_alarm_irq_enable(struct device *dev, unsigned int en)
{
	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
	struct regmap *regmap = chip->regmap;
	unsigned int val;

	val = en ? AC100_ALM_INT_ENABLE : 0;

	return regmap_write(regmap, AC100_ALM_INT_ENA, val);
}

static int ac100_rtc_get_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
	struct regmap *regmap = chip->regmap;
	struct rtc_time *alrm_tm = &alrm->time;
	u16 reg[7];
	unsigned int val;
	int ret;

	ret = regmap_read(regmap, AC100_ALM_INT_ENA, &val);
	if (ret)
		return ret;

	alrm->enabled = !!(val & AC100_ALM_INT_ENABLE);

	ret = regmap_bulk_read(regmap, AC100_ALM_SEC, reg, 7);
	if (ret)
		return ret;

	alrm_tm->tm_sec  = bcd2bin(reg[0] & AC100_ALM_SEC_MASK);
	alrm_tm->tm_min  = bcd2bin(reg[1] & AC100_ALM_MIN_MASK);
	alrm_tm->tm_hour = bcd2bin(reg[2] & AC100_ALM_HOU_MASK);
	alrm_tm->tm_wday = bcd2bin(reg[3] & AC100_ALM_WEE_MASK);
	alrm_tm->tm_mday = bcd2bin(reg[4] & AC100_ALM_DAY_MASK);
	alrm_tm->tm_mon  = bcd2bin(reg[5] & AC100_ALM_MON_MASK) - 1;
	alrm_tm->tm_year = bcd2bin(reg[6] & AC100_ALM_YEA_MASK) +
			   AC100_YEAR_OFF;

	return 0;
}

static int ac100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
	struct regmap *regmap = chip->regmap;
	struct rtc_time *alrm_tm = &alrm->time;
	u16 reg[8];
	int year;
	int ret;

	/* our alarm has a limited year range... */
	year = alrm_tm->tm_year - AC100_YEAR_OFF;
	if (year < 0 || year > (AC100_YEAR_MAX - 1900)) {
		dev_err(dev, "alarm only supports year in range %d - %d\n",
			AC100_YEAR_MIN, AC100_YEAR_MAX);
		return -EINVAL;
	}

	/* convert to BCD */
	reg[0] = (bin2bcd(alrm_tm->tm_sec)  & AC100_ALM_SEC_MASK) |
			AC100_ALM_ENABLE_FLAG;
	reg[1] = (bin2bcd(alrm_tm->tm_min)  & AC100_ALM_MIN_MASK) |
			AC100_ALM_ENABLE_FLAG;
	reg[2] = (bin2bcd(alrm_tm->tm_hour) & AC100_ALM_HOU_MASK) |
			AC100_ALM_ENABLE_FLAG;
	/* Do not enable weekday alarm */
	reg[3] = bin2bcd(alrm_tm->tm_wday) & AC100_ALM_WEE_MASK;
	reg[4] = (bin2bcd(alrm_tm->tm_mday) & AC100_ALM_DAY_MASK) |
			AC100_ALM_ENABLE_FLAG;
	reg[5] = (bin2bcd(alrm_tm->tm_mon + 1)  & AC100_ALM_MON_MASK) |
			AC100_ALM_ENABLE_FLAG;
	reg[6] = (bin2bcd(year) & AC100_ALM_YEA_MASK) |
			AC100_ALM_ENABLE_FLAG;
	/* trigger write */
	reg[7] = AC100_ALM_UPD_TRIGGER;

	ret = regmap_bulk_write(regmap, AC100_ALM_SEC, reg, 8);
	if (ret)
		return ret;

	return ac100_rtc_alarm_irq_enable(dev, alrm->enabled);
}

static irqreturn_t ac100_rtc_irq(int irq, void *data)
{
	struct ac100_rtc_dev *chip = data;
	struct regmap *regmap = chip->regmap;
	unsigned int val = 0;
	int ret;

	mutex_lock(&chip->rtc->ops_lock);

	/* read status */
	ret = regmap_read(regmap, AC100_ALM_INT_STA, &val);
	if (ret)
		goto out;

	if (val & AC100_ALM_INT_ENABLE) {
		/* signal rtc framework */
		rtc_update_irq(chip->rtc, 1, RTC_AF | RTC_IRQF);

		/* clear status */
		ret = regmap_write(regmap, AC100_ALM_INT_STA, val);
		if (ret)
			goto out;

		/* disable interrupt */
		ret = ac100_rtc_alarm_irq_enable(chip->dev, 0);
		if (ret)
			goto out;
	}

out:
	mutex_unlock(&chip->rtc->ops_lock);
	return IRQ_HANDLED;
}

static const struct rtc_class_ops ac100_rtc_ops = {
	.read_time	  = ac100_rtc_get_time,
	.set_time	  = ac100_rtc_set_time,
	.read_alarm	  = ac100_rtc_get_alarm,
	.set_alarm	  = ac100_rtc_set_alarm,
	.alarm_irq_enable = ac100_rtc_alarm_irq_enable,
};

static int ac100_rtc_probe(struct platform_device *pdev)
{
	struct ac100_dev *ac100 = dev_get_drvdata(pdev->dev.parent);
	struct ac100_rtc_dev *chip;
	int ret;

	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
	if (!chip)
		return -ENOMEM;

	platform_set_drvdata(pdev, chip);
	chip->dev = &pdev->dev;
	chip->regmap = ac100->regmap;

	chip->irq = platform_get_irq(pdev, 0);
	if (chip->irq < 0) {
		dev_err(&pdev->dev, "No IRQ resource\n");
		return chip->irq;
	}

	chip->rtc = devm_rtc_allocate_device(&pdev->dev);
	if (IS_ERR(chip->rtc))
		return PTR_ERR(chip->rtc);

	chip->rtc->ops = &ac100_rtc_ops;

	ret = devm_request_threaded_irq(&pdev->dev, chip->irq, NULL,
					ac100_rtc_irq,
					IRQF_SHARED | IRQF_ONESHOT,
					dev_name(&pdev->dev), chip);
	if (ret) {
		dev_err(&pdev->dev, "Could not request IRQ\n");
		return ret;
	}

	/* always use 24 hour mode */
	regmap_write_bits(chip->regmap, AC100_RTC_CTRL, AC100_RTC_CTRL_24HOUR,
			  AC100_RTC_CTRL_24HOUR);

	/* disable counter alarm interrupt */
	regmap_write(chip->regmap, AC100_ALM_INT_ENA, 0);

	/* clear counter alarm pending interrupts */
	regmap_write(chip->regmap, AC100_ALM_INT_STA, AC100_ALM_INT_ENABLE);

	ret = ac100_rtc_register_clks(chip);
	if (ret)
		return ret;

	ret = rtc_register_device(chip->rtc);
	if (ret) {
		dev_err(&pdev->dev, "unable to register device\n");
		return ret;
	}

	dev_info(&pdev->dev, "RTC enabled\n");

	return 0;
}

static int ac100_rtc_remove(struct platform_device *pdev)
{
	struct ac100_rtc_dev *chip = platform_get_drvdata(pdev);

	ac100_rtc_unregister_clks(chip);

	return 0;
}

static const struct of_device_id ac100_rtc_match[] = {
	{ .compatible = "x-powers,ac100-rtc" },
	{ },
};
MODULE_DEVICE_TABLE(of, ac100_rtc_match);

static struct platform_driver ac100_rtc_driver = {
	.probe		= ac100_rtc_probe,
	.remove		= ac100_rtc_remove,
	.driver		= {
		.name		= "ac100-rtc",
		.of_match_table	= of_match_ptr(ac100_rtc_match),
	},
};
module_platform_driver(ac100_rtc_driver);

MODULE_DESCRIPTION("X-Powers AC100 RTC driver");
MODULE_AUTHOR("Chen-Yu Tsai <wens@csie.org>");
MODULE_LICENSE("GPL v2");