// SPDX-License-Identifier: GPL-2.0+
/*
 * Freescale FlexTimer Module (FTM) alarm device driver.
 *
 * Copyright 2014 Freescale Semiconductor, Inc.
 * Copyright 2019-2020 NXP
 *
 */

#include <linux/device.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/fsl/ftm.h>
#include <linux/rtc.h>
#include <linux/time.h>
#include <linux/acpi.h>
#include <linux/pm_wakeirq.h>

#define FTM_SC_CLK(c)           ((c) << FTM_SC_CLK_MASK_SHIFT)

/*
 * Select Fixed frequency clock (32KHz) as clock source
 * of FlexTimer Module
 */
#define FTM_SC_CLKS_FIXED_FREQ  0x02
#define FIXED_FREQ_CLK          32000

/* Select 128 (2^7) as divider factor */
#define MAX_FREQ_DIV            (1 << FTM_SC_PS_MASK)

/* Maximum counter value in FlexTimer's CNT registers */
#define MAX_COUNT_VAL           0xffff

struct ftm_rtc {
        struct rtc_device *rtc_dev;
        void __iomem *base;
        bool big_endian;
        u32 alarm_freq;
};

static inline u32 rtc_readl(struct ftm_rtc *dev, u32 reg)
{
        if (dev->big_endian)
                return ioread32be(dev->base + reg);
        else
                return ioread32(dev->base + reg);
}

static inline void rtc_writel(struct ftm_rtc *dev, u32 reg, u32 val)
{
        if (dev->big_endian)
                iowrite32be(val, dev->base + reg);
        else
                iowrite32(val, dev->base + reg);
}

static inline void ftm_counter_enable(struct ftm_rtc *rtc)
{
        u32 val;

        /* select and enable counter clock source */
        val = rtc_readl(rtc, FTM_SC);
        val &= ~(FTM_SC_PS_MASK | FTM_SC_CLK_MASK);
        val |= (FTM_SC_PS_MASK | FTM_SC_CLK(FTM_SC_CLKS_FIXED_FREQ));
        rtc_writel(rtc, FTM_SC, val);
}

static inline void ftm_counter_disable(struct ftm_rtc *rtc)
{
        u32 val;

        /* disable counter clock source */
        val = rtc_readl(rtc, FTM_SC);
        val &= ~(FTM_SC_PS_MASK | FTM_SC_CLK_MASK);
        rtc_writel(rtc, FTM_SC, val);
}

static inline void ftm_irq_acknowledge(struct ftm_rtc *rtc)
{
        unsigned int timeout = 100;

        /*
         *Fix errata A-007728 for flextimer
         *      If the FTM counter reaches the FTM_MOD value between
         *      the reading of the TOF bit and the writing of 0 to
         *      the TOF bit, the process of clearing the TOF bit
         *      does not work as expected when FTMx_CONF[NUMTOF] != 0
         *      and the current TOF count is less than FTMx_CONF[NUMTOF].
         *      If the above condition is met, the TOF bit remains set.
         *      If the TOF interrupt is enabled (FTMx_SC[TOIE] = 1),the
         *      TOF interrupt also remains asserted.
         *
         *      Above is the errata discription
         *
         *      In one word: software clearing TOF bit not works when
         *      FTMx_CONF[NUMTOF] was seted as nonzero and FTM counter
         *      reaches the FTM_MOD value.
         *
         *      The workaround is clearing TOF bit until it works
         *      (FTM counter doesn't always reache the FTM_MOD anyway),
         *      which may cost some cycles.
         */
        while ((FTM_SC_TOF & rtc_readl(rtc, FTM_SC)) && timeout--)
                rtc_writel(rtc, FTM_SC, rtc_readl(rtc, FTM_SC) & (~FTM_SC_TOF));
}

static inline void ftm_irq_enable(struct ftm_rtc *rtc)
{
        u32 val;

        val = rtc_readl(rtc, FTM_SC);
        val |= FTM_SC_TOIE;
        rtc_writel(rtc, FTM_SC, val);
}

static inline void ftm_irq_disable(struct ftm_rtc *rtc)
{
        u32 val;

        val = rtc_readl(rtc, FTM_SC);
        val &= ~FTM_SC_TOIE;
        rtc_writel(rtc, FTM_SC, val);
}

static inline void ftm_reset_counter(struct ftm_rtc *rtc)
{
        /*
         * The CNT register contains the FTM counter value.
         * Reset clears the CNT register. Writing any value to COUNT
         * updates the counter with its initial value, CNTIN.
         */
        rtc_writel(rtc, FTM_CNT, 0x00);
}

static void ftm_clean_alarm(struct ftm_rtc *rtc)
{
        ftm_counter_disable(rtc);

        rtc_writel(rtc, FTM_CNTIN, 0x00);
        rtc_writel(rtc, FTM_MOD, ~0U);

        ftm_reset_counter(rtc);
}

static irqreturn_t ftm_rtc_alarm_interrupt(int irq, void *dev)
{
        struct ftm_rtc *rtc = dev;

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

        ftm_irq_acknowledge(rtc);
        ftm_irq_disable(rtc);
        ftm_clean_alarm(rtc);

        return IRQ_HANDLED;
}

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

        if (enabled)
                ftm_irq_enable(rtc);
        else
                ftm_irq_disable(rtc);

        return 0;
}

/*
 * Note:
 *      The function is not really getting time from the RTC
 *      since FlexTimer is not a RTC device, but we need to
 *      get time to setup alarm, so we are using system time
 *      for now.
 */
static int ftm_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        rtc_time64_to_tm(ktime_get_real_seconds(), tm);

        return 0;
}

static int ftm_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
{
        return 0;
}

/*
 * 1. Select fixed frequency clock (32KHz) as clock source;
 * 2. Select 128 (2^7) as divider factor;
 * So clock is 250 Hz (32KHz/128).
 *
 * 3. FlexTimer's CNT register is a 32bit register,
 * but the register's 16 bit as counter value,it's other 16 bit
 * is reserved.So minimum counter value is 0x0,maximum counter
 * value is 0xffff.
 * So max alarm value is 262 (65536 / 250) seconds
 */
static int ftm_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
{
        time64_t alm_time;
        unsigned long long cycle;
        struct ftm_rtc *rtc = dev_get_drvdata(dev);

        alm_time = rtc_tm_to_time64(&alm->time);

        ftm_clean_alarm(rtc);
        cycle = (alm_time - ktime_get_real_seconds()) * rtc->alarm_freq;
        if (cycle > MAX_COUNT_VAL) {
                pr_err("Out of alarm range {0~262} seconds.\n");
                return -ERANGE;
        }

        ftm_irq_disable(rtc);

        /*
         * The counter increments until the value of MOD is reached,
         * at which point the counter is reloaded with the value of CNTIN.
         * The TOF (the overflow flag) bit is set when the FTM counter
         * changes from MOD to CNTIN. So we should using the cycle - 1.
         */
        rtc_writel(rtc, FTM_MOD, cycle - 1);

        ftm_counter_enable(rtc);
        ftm_irq_enable(rtc);

        return 0;

}

static const struct rtc_class_ops ftm_rtc_ops = {
        .read_time              = ftm_rtc_read_time,
        .read_alarm             = ftm_rtc_read_alarm,
        .set_alarm              = ftm_rtc_set_alarm,
        .alarm_irq_enable       = ftm_rtc_alarm_irq_enable,
};

static int ftm_rtc_probe(struct platform_device *pdev)
{
        int irq;
        int ret;
        struct ftm_rtc *rtc;

        rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
        if (unlikely(!rtc)) {
                dev_err(&pdev->dev, "cannot alloc memory for rtc\n");
                return -ENOMEM;
        }

        platform_set_drvdata(pdev, rtc);

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

        rtc->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(rtc->base)) {
                dev_err(&pdev->dev, "cannot ioremap resource for rtc\n");
                return PTR_ERR(rtc->base);
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        ret = devm_request_irq(&pdev->dev, irq, ftm_rtc_alarm_interrupt,
                               0, dev_name(&pdev->dev), rtc);
        if (ret < 0) {
                dev_err(&pdev->dev, "failed to request irq\n");
                return ret;
        }

        rtc->big_endian =
                device_property_read_bool(&pdev->dev, "big-endian");

        rtc->alarm_freq = (u32)FIXED_FREQ_CLK / (u32)MAX_FREQ_DIV;
        rtc->rtc_dev->ops = &ftm_rtc_ops;

        device_init_wakeup(&pdev->dev, true);
        ret = dev_pm_set_wake_irq(&pdev->dev, irq);
        if (ret)
                dev_err(&pdev->dev, "failed to enable irq wake\n");

        ret = devm_rtc_register_device(rtc->rtc_dev);
        if (ret) {
                dev_err(&pdev->dev, "can't register rtc device\n");
                return ret;
        }

        return 0;
}

static const struct of_device_id ftm_rtc_match[] = {
        { .compatible = "fsl,ls1012a-ftm-alarm", },
        { .compatible = "fsl,ls1021a-ftm-alarm", },
        { .compatible = "fsl,ls1028a-ftm-alarm", },
        { .compatible = "fsl,ls1043a-ftm-alarm", },
        { .compatible = "fsl,ls1046a-ftm-alarm", },
        { .compatible = "fsl,ls1088a-ftm-alarm", },
        { .compatible = "fsl,ls208xa-ftm-alarm", },
        { .compatible = "fsl,lx2160a-ftm-alarm", },
        { },
};
MODULE_DEVICE_TABLE(of, ftm_rtc_match);

static const struct acpi_device_id ftm_imx_acpi_ids[] __maybe_unused = {
        {"NXP0014",},
        { }
};
MODULE_DEVICE_TABLE(acpi, ftm_imx_acpi_ids);

static struct platform_driver ftm_rtc_driver = {
        .probe          = ftm_rtc_probe,
        .driver         = {
                .name   = "ftm-alarm",
                .of_match_table = ftm_rtc_match,
                .acpi_match_table = ACPI_PTR(ftm_imx_acpi_ids),
        },
};

module_platform_driver(ftm_rtc_driver);

MODULE_DESCRIPTION("NXP/Freescale FlexTimer alarm driver");
MODULE_AUTHOR("Biwen Li <biwen.li@nxp.com>");
MODULE_LICENSE("GPL");