// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * rtc-st-lpc.c - ST's LPC RTC, powered by the Low Power Timer
 *
 * Copyright (C) 2014 STMicroelectronics Limited
 *
 * Author: David Paris <david.paris@st.com> for STMicroelectronics
 *         Lee Jones <lee.jones@linaro.org> for STMicroelectronics
 *
 * Based on the original driver written by Stuart Menefy.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>

#include <dt-bindings/mfd/st-lpc.h>

/* Low Power Timer */
#define LPC_LPT_LSB_OFF         0x400
#define LPC_LPT_MSB_OFF         0x404
#define LPC_LPT_START_OFF       0x408

/* Low Power Alarm */
#define LPC_LPA_LSB_OFF         0x410
#define LPC_LPA_MSB_OFF         0x414
#define LPC_LPA_START_OFF       0x418

/* LPC as WDT */
#define LPC_WDT_OFF             0x510
#define LPC_WDT_FLAG_OFF        0x514

struct st_rtc {
        struct rtc_device *rtc_dev;
        struct rtc_wkalrm alarm;
        struct clk *clk;
        unsigned long clkrate;
        void __iomem *ioaddr;
        bool irq_enabled:1;
        spinlock_t lock;
        short irq;
};

static void st_rtc_set_hw_alarm(struct st_rtc *rtc,
                                unsigned long msb, unsigned long  lsb)
{
        unsigned long flags;

        spin_lock_irqsave(&rtc->lock, flags);

        writel_relaxed(1, rtc->ioaddr + LPC_WDT_OFF);

        writel_relaxed(msb, rtc->ioaddr + LPC_LPA_MSB_OFF);
        writel_relaxed(lsb, rtc->ioaddr + LPC_LPA_LSB_OFF);
        writel_relaxed(1, rtc->ioaddr + LPC_LPA_START_OFF);

        writel_relaxed(0, rtc->ioaddr + LPC_WDT_OFF);

        spin_unlock_irqrestore(&rtc->lock, flags);
}

static irqreturn_t st_rtc_handler(int this_irq, void *data)
{
        struct st_rtc *rtc = (struct st_rtc *)data;

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

        return IRQ_HANDLED;
}

static int st_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct st_rtc *rtc = dev_get_drvdata(dev);
        unsigned long lpt_lsb, lpt_msb;
        unsigned long long lpt;
        unsigned long flags;

        spin_lock_irqsave(&rtc->lock, flags);

        do {
                lpt_msb = readl_relaxed(rtc->ioaddr + LPC_LPT_MSB_OFF);
                lpt_lsb = readl_relaxed(rtc->ioaddr + LPC_LPT_LSB_OFF);
        } while (readl_relaxed(rtc->ioaddr + LPC_LPT_MSB_OFF) != lpt_msb);

        spin_unlock_irqrestore(&rtc->lock, flags);

        lpt = ((unsigned long long)lpt_msb << 32) | lpt_lsb;
        do_div(lpt, rtc->clkrate);
        rtc_time64_to_tm(lpt, tm);

        return 0;
}

static int st_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct st_rtc *rtc = dev_get_drvdata(dev);
        unsigned long long lpt, secs;
        unsigned long flags;

        secs = rtc_tm_to_time64(tm);

        lpt = (unsigned long long)secs * rtc->clkrate;

        spin_lock_irqsave(&rtc->lock, flags);

        writel_relaxed(lpt >> 32, rtc->ioaddr + LPC_LPT_MSB_OFF);
        writel_relaxed(lpt, rtc->ioaddr + LPC_LPT_LSB_OFF);
        writel_relaxed(1, rtc->ioaddr + LPC_LPT_START_OFF);

        spin_unlock_irqrestore(&rtc->lock, flags);

        return 0;
}

static int st_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
        struct st_rtc *rtc = dev_get_drvdata(dev);
        unsigned long flags;

        spin_lock_irqsave(&rtc->lock, flags);

        memcpy(wkalrm, &rtc->alarm, sizeof(struct rtc_wkalrm));

        spin_unlock_irqrestore(&rtc->lock, flags);

        return 0;
}

static int st_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct st_rtc *rtc = dev_get_drvdata(dev);

        if (enabled && !rtc->irq_enabled) {
                enable_irq(rtc->irq);
                rtc->irq_enabled = true;
        } else if (!enabled && rtc->irq_enabled) {
                disable_irq(rtc->irq);
                rtc->irq_enabled = false;
        }

        return 0;
}

static int st_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct st_rtc *rtc = dev_get_drvdata(dev);
        struct rtc_time now;
        unsigned long long now_secs;
        unsigned long long alarm_secs;
        unsigned long long lpa;

        st_rtc_read_time(dev, &now);
        now_secs = rtc_tm_to_time64(&now);
        alarm_secs = rtc_tm_to_time64(&t->time);

        memcpy(&rtc->alarm, t, sizeof(struct rtc_wkalrm));

        /* Now many secs to fire */
        alarm_secs -= now_secs;
        lpa = (unsigned long long)alarm_secs * rtc->clkrate;

        st_rtc_set_hw_alarm(rtc, lpa >> 32, lpa);
        st_rtc_alarm_irq_enable(dev, t->enabled);

        return 0;
}

static const struct rtc_class_ops st_rtc_ops = {
        .read_time              = st_rtc_read_time,
        .set_time               = st_rtc_set_time,
        .read_alarm             = st_rtc_read_alarm,
        .set_alarm              = st_rtc_set_alarm,
        .alarm_irq_enable       = st_rtc_alarm_irq_enable,
};

static int st_rtc_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct st_rtc *rtc;
        uint32_t mode;
        int ret = 0;

        ret = of_property_read_u32(np, "st,lpc-mode", &mode);
        if (ret) {
                dev_err(&pdev->dev, "An LPC mode must be provided\n");
                return -EINVAL;
        }

        /* LPC can either run as a Clocksource or in RTC or WDT mode */
        if (mode != ST_LPC_MODE_RTC)
                return -ENODEV;

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

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

        spin_lock_init(&rtc->lock);

        rtc->ioaddr = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(rtc->ioaddr))
                return PTR_ERR(rtc->ioaddr);

        rtc->irq = irq_of_parse_and_map(np, 0);
        if (!rtc->irq) {
                dev_err(&pdev->dev, "IRQ missing or invalid\n");
                return -EINVAL;
        }

        ret = devm_request_irq(&pdev->dev, rtc->irq, st_rtc_handler,
                               IRQF_NO_AUTOEN, pdev->name, rtc);
        if (ret) {
                dev_err(&pdev->dev, "Failed to request irq %i\n", rtc->irq);
                return ret;
        }

        enable_irq_wake(rtc->irq);

        rtc->clk = devm_clk_get_enabled(&pdev->dev, NULL);
        if (IS_ERR(rtc->clk))
                return dev_err_probe(&pdev->dev, PTR_ERR(rtc->clk),
                                     "Unable to request clock\n");

        rtc->clkrate = clk_get_rate(rtc->clk);
        if (!rtc->clkrate) {
                dev_err(&pdev->dev, "Unable to fetch clock rate\n");
                return -EINVAL;
        }

        device_set_wakeup_capable(&pdev->dev, 1);

        platform_set_drvdata(pdev, rtc);

        rtc->rtc_dev->ops = &st_rtc_ops;
        rtc->rtc_dev->range_max = U64_MAX;
        do_div(rtc->rtc_dev->range_max, rtc->clkrate);

        ret = devm_rtc_register_device(rtc->rtc_dev);
        if (ret)
                return ret;

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int st_rtc_suspend(struct device *dev)
{
        struct st_rtc *rtc = dev_get_drvdata(dev);

        if (device_may_wakeup(dev))
                return 0;

        writel_relaxed(1, rtc->ioaddr + LPC_WDT_OFF);
        writel_relaxed(0, rtc->ioaddr + LPC_LPA_START_OFF);
        writel_relaxed(0, rtc->ioaddr + LPC_WDT_OFF);

        return 0;
}

static int st_rtc_resume(struct device *dev)
{
        struct st_rtc *rtc = dev_get_drvdata(dev);

        rtc_alarm_irq_enable(rtc->rtc_dev, 0);

        /*
         * clean 'rtc->alarm' to allow a new
         * .set_alarm to the upper RTC layer
         */
        memset(&rtc->alarm, 0, sizeof(struct rtc_wkalrm));

        writel_relaxed(0, rtc->ioaddr + LPC_LPA_MSB_OFF);
        writel_relaxed(0, rtc->ioaddr + LPC_LPA_LSB_OFF);
        writel_relaxed(1, rtc->ioaddr + LPC_WDT_OFF);
        writel_relaxed(1, rtc->ioaddr + LPC_LPA_START_OFF);
        writel_relaxed(0, rtc->ioaddr + LPC_WDT_OFF);

        return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(st_rtc_pm_ops, st_rtc_suspend, st_rtc_resume);

static const struct of_device_id st_rtc_match[] = {
        { .compatible = "st,stih407-lpc" },
        {}
};
MODULE_DEVICE_TABLE(of, st_rtc_match);

static struct platform_driver st_rtc_platform_driver = {
        .driver = {
                .name = "st-lpc-rtc",
                .pm = &st_rtc_pm_ops,
                .of_match_table = st_rtc_match,
        },
        .probe = st_rtc_probe,
};

module_platform_driver(st_rtc_platform_driver);

MODULE_DESCRIPTION("STMicroelectronics LPC RTC driver");
MODULE_AUTHOR("David Paris <david.paris@st.com>");
MODULE_LICENSE("GPL");