/*
 * RTC driver for the Armada 38x Marvell SoCs
 *
 * Copyright (C) 2015 Marvell
 *
 * Gregory Clement <gregory.clement@free-electrons.com>
 *
 * 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; either version 2 of the
 * License, or (at your option) any later version.
 *
 */

#include <linux/delay.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>

#define RTC_STATUS	    0x0
#define RTC_STATUS_ALARM1	    BIT(0)
#define RTC_STATUS_ALARM2	    BIT(1)
#define RTC_IRQ1_CONF	    0x4
#define RTC_IRQ2_CONF	    0x8
#define RTC_IRQ_AL_EN		    BIT(0)
#define RTC_IRQ_FREQ_EN		    BIT(1)
#define RTC_IRQ_FREQ_1HZ	    BIT(2)
#define RTC_CCR		    0x18
#define RTC_CCR_MODE		    BIT(15)
#define RTC_CONF_TEST	    0x1C
#define RTC_NOMINAL_TIMING	    BIT(13)

#define RTC_TIME	    0xC
#define RTC_ALARM1	    0x10
#define RTC_ALARM2	    0x14

/* Armada38x SoC registers  */
#define RTC_38X_BRIDGE_TIMING_CTL   0x0
#define RTC_38X_PERIOD_OFFS		0
#define RTC_38X_PERIOD_MASK		(0x3FF << RTC_38X_PERIOD_OFFS)
#define RTC_38X_READ_DELAY_OFFS		26
#define RTC_38X_READ_DELAY_MASK		(0x1F << RTC_38X_READ_DELAY_OFFS)

/* Armada 7K/8K registers  */
#define RTC_8K_BRIDGE_TIMING_CTL0    0x0
#define RTC_8K_WRCLK_PERIOD_OFFS	0
#define RTC_8K_WRCLK_PERIOD_MASK	(0xFFFF << RTC_8K_WRCLK_PERIOD_OFFS)
#define RTC_8K_WRCLK_SETUP_OFFS		16
#define RTC_8K_WRCLK_SETUP_MASK		(0xFFFF << RTC_8K_WRCLK_SETUP_OFFS)
#define RTC_8K_BRIDGE_TIMING_CTL1   0x4
#define RTC_8K_READ_DELAY_OFFS		0
#define RTC_8K_READ_DELAY_MASK		(0xFFFF << RTC_8K_READ_DELAY_OFFS)

#define RTC_8K_ISR		    0x10
#define RTC_8K_IMR		    0x14
#define RTC_8K_ALARM2			BIT(0)

#define SOC_RTC_INTERRUPT	    0x8
#define SOC_RTC_ALARM1			BIT(0)
#define SOC_RTC_ALARM2			BIT(1)
#define SOC_RTC_ALARM1_MASK		BIT(2)
#define SOC_RTC_ALARM2_MASK		BIT(3)

#define SAMPLE_NR 100

struct value_to_freq {
	u32 value;
	u8 freq;
};

struct armada38x_rtc {
	struct rtc_device   *rtc_dev;
	void __iomem	    *regs;
	void __iomem	    *regs_soc;
	spinlock_t	    lock;
	int		    irq;
	bool		    initialized;
	struct value_to_freq *val_to_freq;
	struct armada38x_rtc_data *data;
};

#define ALARM1	0
#define ALARM2	1

#define ALARM_REG(base, alarm)	 ((base) + (alarm) * sizeof(u32))

struct armada38x_rtc_data {
	/* Initialize the RTC-MBUS bridge timing */
	void (*update_mbus_timing)(struct armada38x_rtc *rtc);
	u32 (*read_rtc_reg)(struct armada38x_rtc *rtc, u8 rtc_reg);
	void (*clear_isr)(struct armada38x_rtc *rtc);
	void (*unmask_interrupt)(struct armada38x_rtc *rtc);
	u32 alarm;
};

/*
 * According to the datasheet, the OS should wait 5us after every
 * register write to the RTC hard macro so that the required update
 * can occur without holding off the system bus
 * According to errata RES-3124064, Write to any RTC register
 * may fail. As a workaround, before writing to RTC
 * register, issue a dummy write of 0x0 twice to RTC Status
 * register.
 */

static void rtc_delayed_write(u32 val, struct armada38x_rtc *rtc, int offset)
{
	writel(0, rtc->regs + RTC_STATUS);
	writel(0, rtc->regs + RTC_STATUS);
	writel(val, rtc->regs + offset);
	udelay(5);
}

/* Update RTC-MBUS bridge timing parameters */
static void rtc_update_38x_mbus_timing_params(struct armada38x_rtc *rtc)
{
	u32 reg;

	reg = readl(rtc->regs_soc + RTC_38X_BRIDGE_TIMING_CTL);
	reg &= ~RTC_38X_PERIOD_MASK;
	reg |= 0x3FF << RTC_38X_PERIOD_OFFS; /* Maximum value */
	reg &= ~RTC_38X_READ_DELAY_MASK;
	reg |= 0x1F << RTC_38X_READ_DELAY_OFFS; /* Maximum value */
	writel(reg, rtc->regs_soc + RTC_38X_BRIDGE_TIMING_CTL);
}

static void rtc_update_8k_mbus_timing_params(struct armada38x_rtc *rtc)
{
	u32 reg;

	reg = readl(rtc->regs_soc + RTC_8K_BRIDGE_TIMING_CTL0);
	reg &= ~RTC_8K_WRCLK_PERIOD_MASK;
	reg |= 0x3FF << RTC_8K_WRCLK_PERIOD_OFFS;
	reg &= ~RTC_8K_WRCLK_SETUP_MASK;
	reg |= 0x29 << RTC_8K_WRCLK_SETUP_OFFS;
	writel(reg, rtc->regs_soc + RTC_8K_BRIDGE_TIMING_CTL0);

	reg = readl(rtc->regs_soc + RTC_8K_BRIDGE_TIMING_CTL1);
	reg &= ~RTC_8K_READ_DELAY_MASK;
	reg |= 0x3F << RTC_8K_READ_DELAY_OFFS;
	writel(reg, rtc->regs_soc + RTC_8K_BRIDGE_TIMING_CTL1);
}

static u32 read_rtc_register(struct armada38x_rtc *rtc, u8 rtc_reg)
{
	return readl(rtc->regs + rtc_reg);
}

static u32 read_rtc_register_38x_wa(struct armada38x_rtc *rtc, u8 rtc_reg)
{
	int i, index_max = 0, max = 0;

	for (i = 0; i < SAMPLE_NR; i++) {
		rtc->val_to_freq[i].value = readl(rtc->regs + rtc_reg);
		rtc->val_to_freq[i].freq = 0;
	}

	for (i = 0; i < SAMPLE_NR; i++) {
		int j = 0;
		u32 value = rtc->val_to_freq[i].value;

		while (rtc->val_to_freq[j].freq) {
			if (rtc->val_to_freq[j].value == value) {
				rtc->val_to_freq[j].freq++;
				break;
			}
			j++;
		}

		if (!rtc->val_to_freq[j].freq) {
			rtc->val_to_freq[j].value = value;
			rtc->val_to_freq[j].freq = 1;
		}

		if (rtc->val_to_freq[j].freq > max) {
			index_max = j;
			max = rtc->val_to_freq[j].freq;
		}

		/*
		 * If a value already has half of the sample this is the most
		 * frequent one and we can stop the research right now
		 */
		if (max > SAMPLE_NR / 2)
			break;
	}

	return rtc->val_to_freq[index_max].value;
}

static void armada38x_clear_isr(struct armada38x_rtc *rtc)
{
	u32 val = readl(rtc->regs_soc + SOC_RTC_INTERRUPT);

	writel(val & ~SOC_RTC_ALARM1, rtc->regs_soc + SOC_RTC_INTERRUPT);
}

static void armada38x_unmask_interrupt(struct armada38x_rtc *rtc)
{
	u32 val = readl(rtc->regs_soc + SOC_RTC_INTERRUPT);

	writel(val | SOC_RTC_ALARM1_MASK, rtc->regs_soc + SOC_RTC_INTERRUPT);
}

static void armada8k_clear_isr(struct armada38x_rtc *rtc)
{
	writel(RTC_8K_ALARM2, rtc->regs_soc + RTC_8K_ISR);
}

static void armada8k_unmask_interrupt(struct armada38x_rtc *rtc)
{
	writel(RTC_8K_ALARM2, rtc->regs_soc + RTC_8K_IMR);
}

static int armada38x_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct armada38x_rtc *rtc = dev_get_drvdata(dev);
	unsigned long time, flags;

	spin_lock_irqsave(&rtc->lock, flags);
	time = rtc->data->read_rtc_reg(rtc, RTC_TIME);
	spin_unlock_irqrestore(&rtc->lock, flags);

	rtc_time_to_tm(time, tm);

	return 0;
}

static void armada38x_rtc_reset(struct armada38x_rtc *rtc)
{
	u32 reg;

	reg = rtc->data->read_rtc_reg(rtc, RTC_CONF_TEST);
	/* If bits [7:0] are non-zero, assume RTC was uninitialized */
	if (reg & 0xff) {
		rtc_delayed_write(0, rtc, RTC_CONF_TEST);
		msleep(500); /* Oscillator startup time */
		rtc_delayed_write(0, rtc, RTC_TIME);
		rtc_delayed_write(SOC_RTC_ALARM1 | SOC_RTC_ALARM2, rtc,
				  RTC_STATUS);
		rtc_delayed_write(RTC_NOMINAL_TIMING, rtc, RTC_CCR);
	}
	rtc->initialized = true;
}

static int armada38x_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct armada38x_rtc *rtc = dev_get_drvdata(dev);
	int ret = 0;
	unsigned long time, flags;

	ret = rtc_tm_to_time(tm, &time);

	if (ret)
		goto out;

	if (!rtc->initialized)
		armada38x_rtc_reset(rtc);

	spin_lock_irqsave(&rtc->lock, flags);
	rtc_delayed_write(time, rtc, RTC_TIME);
	spin_unlock_irqrestore(&rtc->lock, flags);

out:
	return ret;
}

static int armada38x_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct armada38x_rtc *rtc = dev_get_drvdata(dev);
	unsigned long time, flags;
	u32 reg = ALARM_REG(RTC_ALARM1, rtc->data->alarm);
	u32 reg_irq = ALARM_REG(RTC_IRQ1_CONF, rtc->data->alarm);
	u32 val;

	spin_lock_irqsave(&rtc->lock, flags);

	time = rtc->data->read_rtc_reg(rtc, reg);
	val = rtc->data->read_rtc_reg(rtc, reg_irq) & RTC_IRQ_AL_EN;

	spin_unlock_irqrestore(&rtc->lock, flags);

	alrm->enabled = val ? 1 : 0;
	rtc_time_to_tm(time,  &alrm->time);

	return 0;
}

static int armada38x_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct armada38x_rtc *rtc = dev_get_drvdata(dev);
	u32 reg = ALARM_REG(RTC_ALARM1, rtc->data->alarm);
	u32 reg_irq = ALARM_REG(RTC_IRQ1_CONF, rtc->data->alarm);
	unsigned long time, flags;
	int ret = 0;

	ret = rtc_tm_to_time(&alrm->time, &time);

	if (ret)
		goto out;

	spin_lock_irqsave(&rtc->lock, flags);

	rtc_delayed_write(time, rtc, reg);

	if (alrm->enabled) {
		rtc_delayed_write(RTC_IRQ_AL_EN, rtc, reg_irq);
		rtc->data->unmask_interrupt(rtc);
	}

	spin_unlock_irqrestore(&rtc->lock, flags);

out:
	return ret;
}

static int armada38x_rtc_alarm_irq_enable(struct device *dev,
					 unsigned int enabled)
{
	struct armada38x_rtc *rtc = dev_get_drvdata(dev);
	u32 reg_irq = ALARM_REG(RTC_IRQ1_CONF, rtc->data->alarm);
	unsigned long flags;

	spin_lock_irqsave(&rtc->lock, flags);

	if (enabled)
		rtc_delayed_write(RTC_IRQ_AL_EN, rtc, reg_irq);
	else
		rtc_delayed_write(0, rtc, reg_irq);

	spin_unlock_irqrestore(&rtc->lock, flags);

	return 0;
}

static irqreturn_t armada38x_rtc_alarm_irq(int irq, void *data)
{
	struct armada38x_rtc *rtc = data;
	u32 val;
	int event = RTC_IRQF | RTC_AF;
	u32 reg_irq = ALARM_REG(RTC_IRQ1_CONF, rtc->data->alarm);

	dev_dbg(&rtc->rtc_dev->dev, "%s:irq(%d)\n", __func__, irq);

	spin_lock(&rtc->lock);

	rtc->data->clear_isr(rtc);
	val = rtc->data->read_rtc_reg(rtc, reg_irq);
	/* disable all the interrupts for alarm*/
	rtc_delayed_write(0, rtc, reg_irq);
	/* Ack the event */
	rtc_delayed_write(1 << rtc->data->alarm, rtc, RTC_STATUS);

	spin_unlock(&rtc->lock);

	if (val & RTC_IRQ_FREQ_EN) {
		if (val & RTC_IRQ_FREQ_1HZ)
			event |= RTC_UF;
		else
			event |= RTC_PF;
	}

	rtc_update_irq(rtc->rtc_dev, 1, event);

	return IRQ_HANDLED;
}

/*
 * The information given in the Armada 388 functional spec is complex.
 * They give two different formulas for calculating the offset value,
 * but when considering "Offset" as an 8-bit signed integer, they both
 * reduce down to (we shall rename "Offset" as "val" here):
 *
 *   val = (f_ideal / f_measured - 1) / resolution   where f_ideal = 32768
 *
 * Converting to time, f = 1/t:
 *   val = (t_measured / t_ideal - 1) / resolution   where t_ideal = 1/32768
 *
 *   =>  t_measured / t_ideal = val * resolution + 1
 *
 * "offset" in the RTC interface is defined as:
 *   t = t0 * (1 + offset * 1e-9)
 * where t is the desired period, t0 is the measured period with a zero
 * offset, which is t_measured above. With t0 = t_measured and t = t_ideal,
 *   offset = (t_ideal / t_measured - 1) / 1e-9
 *
 *   => t_ideal / t_measured = offset * 1e-9 + 1
 *
 * so:
 *
 *   offset * 1e-9 + 1 = 1 / (val * resolution + 1)
 *
 * We want "resolution" to be an integer, so resolution = R * 1e-9, giving
 *   offset = 1e18 / (val * R + 1e9) - 1e9
 *   val = (1e18 / (offset + 1e9) - 1e9) / R
 * with a common transformation:
 *   f(x) = 1e18 / (x + 1e9) - 1e9
 *   offset = f(val * R)
 *   val = f(offset) / R
 *
 * Armada 38x supports two modes, fine mode (954ppb) and coarse mode (3815ppb).
 */
static long armada38x_ppb_convert(long ppb)
{
	long div = ppb + 1000000000L;

	return div_s64(1000000000000000000LL + div / 2, div) - 1000000000L;
}

static int armada38x_rtc_read_offset(struct device *dev, long *offset)
{
	struct armada38x_rtc *rtc = dev_get_drvdata(dev);
	unsigned long ccr, flags;
	long ppb_cor;

	spin_lock_irqsave(&rtc->lock, flags);
	ccr = rtc->data->read_rtc_reg(rtc, RTC_CCR);
	spin_unlock_irqrestore(&rtc->lock, flags);

	ppb_cor = (ccr & RTC_CCR_MODE ? 3815 : 954) * (s8)ccr;
	/* ppb_cor + 1000000000L can never be zero */
	*offset = armada38x_ppb_convert(ppb_cor);

	return 0;
}

static int armada38x_rtc_set_offset(struct device *dev, long offset)
{
	struct armada38x_rtc *rtc = dev_get_drvdata(dev);
	unsigned long ccr = 0;
	long ppb_cor, off;

	/*
	 * The maximum ppb_cor is -128 * 3815 .. 127 * 3815, but we
	 * need to clamp the input.  This equates to -484270 .. 488558.
	 * Not only is this to stop out of range "off" but also to
	 * avoid the division by zero in armada38x_ppb_convert().
	 */
	offset = clamp(offset, -484270L, 488558L);

	ppb_cor = armada38x_ppb_convert(offset);

	/*
	 * Use low update mode where possible, which gives a better
	 * resolution of correction.
	 */
	off = DIV_ROUND_CLOSEST(ppb_cor, 954);
	if (off > 127 || off < -128) {
		ccr = RTC_CCR_MODE;
		off = DIV_ROUND_CLOSEST(ppb_cor, 3815);
	}

	/*
	 * Armada 388 requires a bit pattern in bits 14..8 depending on
	 * the sign bit: { 0, ~S, S, S, S, S, S }
	 */
	ccr |= (off & 0x3fff) ^ 0x2000;
	rtc_delayed_write(ccr, rtc, RTC_CCR);

	return 0;
}

static const struct rtc_class_ops armada38x_rtc_ops = {
	.read_time = armada38x_rtc_read_time,
	.set_time = armada38x_rtc_set_time,
	.read_alarm = armada38x_rtc_read_alarm,
	.set_alarm = armada38x_rtc_set_alarm,
	.alarm_irq_enable = armada38x_rtc_alarm_irq_enable,
	.read_offset = armada38x_rtc_read_offset,
	.set_offset = armada38x_rtc_set_offset,
};

static const struct rtc_class_ops armada38x_rtc_ops_noirq = {
	.read_time = armada38x_rtc_read_time,
	.set_time = armada38x_rtc_set_time,
	.read_alarm = armada38x_rtc_read_alarm,
	.read_offset = armada38x_rtc_read_offset,
	.set_offset = armada38x_rtc_set_offset,
};

static const struct armada38x_rtc_data armada38x_data = {
	.update_mbus_timing = rtc_update_38x_mbus_timing_params,
	.read_rtc_reg = read_rtc_register_38x_wa,
	.clear_isr = armada38x_clear_isr,
	.unmask_interrupt = armada38x_unmask_interrupt,
	.alarm = ALARM1,
};

static const struct armada38x_rtc_data armada8k_data = {
	.update_mbus_timing = rtc_update_8k_mbus_timing_params,
	.read_rtc_reg = read_rtc_register,
	.clear_isr = armada8k_clear_isr,
	.unmask_interrupt = armada8k_unmask_interrupt,
	.alarm = ALARM2,
};

#ifdef CONFIG_OF
static const struct of_device_id armada38x_rtc_of_match_table[] = {
	{
		.compatible = "marvell,armada-380-rtc",
		.data = &armada38x_data,
	},
	{
		.compatible = "marvell,armada-8k-rtc",
		.data = &armada8k_data,
	},
	{}
};
MODULE_DEVICE_TABLE(of, armada38x_rtc_of_match_table);
#endif

static __init int armada38x_rtc_probe(struct platform_device *pdev)
{
	struct resource *res;
	struct armada38x_rtc *rtc;
	const struct of_device_id *match;
	int ret;

	match = of_match_device(armada38x_rtc_of_match_table, &pdev->dev);
	if (!match)
		return -ENODEV;

	rtc = devm_kzalloc(&pdev->dev, sizeof(struct armada38x_rtc),
			    GFP_KERNEL);
	if (!rtc)
		return -ENOMEM;

	rtc->val_to_freq = devm_kcalloc(&pdev->dev, SAMPLE_NR,
				sizeof(struct value_to_freq), GFP_KERNEL);
	if (!rtc->val_to_freq)
		return -ENOMEM;

	spin_lock_init(&rtc->lock);

	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "rtc");
	rtc->regs = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(rtc->regs))
		return PTR_ERR(rtc->regs);
	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "rtc-soc");
	rtc->regs_soc = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(rtc->regs_soc))
		return PTR_ERR(rtc->regs_soc);

	rtc->irq = platform_get_irq(pdev, 0);

	if (rtc->irq < 0) {
		dev_err(&pdev->dev, "no irq\n");
		return rtc->irq;
	}

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

	if (devm_request_irq(&pdev->dev, rtc->irq, armada38x_rtc_alarm_irq,
				0, pdev->name, rtc) < 0) {
		dev_warn(&pdev->dev, "Interrupt not available.\n");
		rtc->irq = -1;
	}
	platform_set_drvdata(pdev, rtc);

	if (rtc->irq != -1) {
		device_init_wakeup(&pdev->dev, 1);
		rtc->rtc_dev->ops = &armada38x_rtc_ops;
	} else {
		/*
		 * If there is no interrupt available then we can't
		 * use the alarm
		 */
		rtc->rtc_dev->ops = &armada38x_rtc_ops_noirq;
	}
	rtc->data = (struct armada38x_rtc_data *)match->data;

	/* Update RTC-MBUS bridge timing parameters */
	rtc->data->update_mbus_timing(rtc);

	ret = rtc_register_device(rtc->rtc_dev);
	if (ret)
		dev_err(&pdev->dev, "Failed to register RTC device: %d\n", ret);

	return ret;
}

#ifdef CONFIG_PM_SLEEP
static int armada38x_rtc_suspend(struct device *dev)
{
	if (device_may_wakeup(dev)) {
		struct armada38x_rtc *rtc = dev_get_drvdata(dev);

		return enable_irq_wake(rtc->irq);
	}

	return 0;
}

static int armada38x_rtc_resume(struct device *dev)
{
	if (device_may_wakeup(dev)) {
		struct armada38x_rtc *rtc = dev_get_drvdata(dev);

		/* Update RTC-MBUS bridge timing parameters */
		rtc->data->update_mbus_timing(rtc);

		return disable_irq_wake(rtc->irq);
	}

	return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(armada38x_rtc_pm_ops,
			 armada38x_rtc_suspend, armada38x_rtc_resume);

static struct platform_driver armada38x_rtc_driver = {
	.driver		= {
		.name	= "armada38x-rtc",
		.pm	= &armada38x_rtc_pm_ops,
		.of_match_table = of_match_ptr(armada38x_rtc_of_match_table),
	},
};

module_platform_driver_probe(armada38x_rtc_driver, armada38x_rtc_probe);

MODULE_DESCRIPTION("Marvell Armada 38x RTC driver");
MODULE_AUTHOR("Gregory CLEMENT <gregory.clement@free-electrons.com>");
MODULE_LICENSE("GPL");