// SPDX-License-Identifier: GPL-2.0+
/*
 * Watchdog driver for Marvell Armada 37xx SoCs
 *
 * Author: Marek Behún <kabel@kernel.org>
 */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/types.h>
#include <linux/watchdog.h>

/*
 * There are four counters that can be used for watchdog on Armada 37xx.
 * The addresses for counter control registers are register base plus ID*0x10,
 * where ID is 0, 1, 2 or 3.
 *
 * In this driver we use IDs 0 and 1. Counter ID 1 is used as watchdog counter,
 * while counter ID 0 is used to implement pinging the watchdog: counter ID 1 is
 * set to restart counting from initial value on counter ID 0 end count event.
 * Pinging is done by forcing immediate end count event on counter ID 0.
 * If only one counter was used, pinging would have to be implemented by
 * disabling and enabling the counter, leaving the system in a vulnerable state
 * for a (really) short period of time.
 *
 * Counters ID 2 and 3 are enabled by default even before U-Boot loads,
 * therefore this driver does not provide a way to use them, eg. by setting a
 * property in device tree.
 */

#define CNTR_ID_RETRIGGER               0
#define CNTR_ID_WDOG                    1

/* relative to cpu_misc */
#define WDT_TIMER_SELECT                0x64
#define WDT_TIMER_SELECT_MASK           0xf
#define WDT_TIMER_SELECT_VAL            BIT(CNTR_ID_WDOG)

/* relative to reg */
#define CNTR_CTRL(id)                   ((id) * 0x10)
#define CNTR_CTRL_ENABLE                0x0001
#define CNTR_CTRL_ACTIVE                0x0002
#define CNTR_CTRL_MODE_MASK             0x000c
#define CNTR_CTRL_MODE_ONESHOT          0x0000
#define CNTR_CTRL_MODE_HWSIG            0x000c
#define CNTR_CTRL_TRIG_SRC_MASK         0x00f0
#define CNTR_CTRL_TRIG_SRC_PREV_CNTR    0x0050
#define CNTR_CTRL_PRESCALE_MASK         0xff00
#define CNTR_CTRL_PRESCALE_MIN          2
#define CNTR_CTRL_PRESCALE_SHIFT        8

#define CNTR_COUNT_LOW(id)              (CNTR_CTRL(id) + 0x4)
#define CNTR_COUNT_HIGH(id)             (CNTR_CTRL(id) + 0x8)

#define WATCHDOG_TIMEOUT                120

static unsigned int timeout;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
                           __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

struct armada_37xx_watchdog {
        struct watchdog_device wdt;
        struct regmap *cpu_misc;
        void __iomem *reg;
        u64 timeout; /* in clock ticks */
        unsigned long clk_rate;
        struct clk *clk;
};

static u64 get_counter_value(struct armada_37xx_watchdog *dev, int id)
{
        u64 val;

        /*
         * when low is read, high is latched into flip-flops so that it can be
         * read consistently without using software debouncing
         */
        val = readl(dev->reg + CNTR_COUNT_LOW(id));
        val |= ((u64)readl(dev->reg + CNTR_COUNT_HIGH(id))) << 32;

        return val;
}

static void set_counter_value(struct armada_37xx_watchdog *dev, int id, u64 val)
{
        writel(val & 0xffffffff, dev->reg + CNTR_COUNT_LOW(id));
        writel(val >> 32, dev->reg + CNTR_COUNT_HIGH(id));
}

static void counter_enable(struct armada_37xx_watchdog *dev, int id)
{
        u32 reg;

        reg = readl(dev->reg + CNTR_CTRL(id));
        reg |= CNTR_CTRL_ENABLE;
        writel(reg, dev->reg + CNTR_CTRL(id));
}

static void counter_disable(struct armada_37xx_watchdog *dev, int id)
{
        u32 reg;

        reg = readl(dev->reg + CNTR_CTRL(id));
        reg &= ~CNTR_CTRL_ENABLE;
        writel(reg, dev->reg + CNTR_CTRL(id));
}

static void init_counter(struct armada_37xx_watchdog *dev, int id, u32 mode,
                         u32 trig_src)
{
        u32 reg;

        reg = readl(dev->reg + CNTR_CTRL(id));

        reg &= ~(CNTR_CTRL_MODE_MASK | CNTR_CTRL_PRESCALE_MASK |
                 CNTR_CTRL_TRIG_SRC_MASK);

        /* set mode */
        reg |= mode & CNTR_CTRL_MODE_MASK;

        /* set prescaler to the min value */
        reg |= CNTR_CTRL_PRESCALE_MIN << CNTR_CTRL_PRESCALE_SHIFT;

        /* set trigger source */
        reg |= trig_src & CNTR_CTRL_TRIG_SRC_MASK;

        writel(reg, dev->reg + CNTR_CTRL(id));
}

static int armada_37xx_wdt_ping(struct watchdog_device *wdt)
{
        struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);

        /* counter 1 is retriggered by forcing end count on counter 0 */
        counter_disable(dev, CNTR_ID_RETRIGGER);
        counter_enable(dev, CNTR_ID_RETRIGGER);

        return 0;
}

static unsigned int armada_37xx_wdt_get_timeleft(struct watchdog_device *wdt)
{
        struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
        u64 res;

        res = get_counter_value(dev, CNTR_ID_WDOG) * CNTR_CTRL_PRESCALE_MIN;
        do_div(res, dev->clk_rate);

        return res;
}

static int armada_37xx_wdt_set_timeout(struct watchdog_device *wdt,
                                       unsigned int timeout)
{
        struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);

        wdt->timeout = timeout;

        /*
         * Compute the timeout in clock rate. We use smallest possible
         * prescaler, which divides the clock rate by 2
         * (CNTR_CTRL_PRESCALE_MIN).
         */
        dev->timeout = (u64)dev->clk_rate * timeout;
        do_div(dev->timeout, CNTR_CTRL_PRESCALE_MIN);

        set_counter_value(dev, CNTR_ID_WDOG, dev->timeout);

        return 0;
}

static bool armada_37xx_wdt_is_running(struct armada_37xx_watchdog *dev)
{
        u32 reg;

        regmap_read(dev->cpu_misc, WDT_TIMER_SELECT, &reg);
        if ((reg & WDT_TIMER_SELECT_MASK) != WDT_TIMER_SELECT_VAL)
                return false;

        reg = readl(dev->reg + CNTR_CTRL(CNTR_ID_WDOG));
        return !!(reg & CNTR_CTRL_ACTIVE);
}

static int armada_37xx_wdt_start(struct watchdog_device *wdt)
{
        struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);

        /* select counter 1 as watchdog counter */
        regmap_write(dev->cpu_misc, WDT_TIMER_SELECT, WDT_TIMER_SELECT_VAL);

        /* init counter 0 as retrigger counter for counter 1 */
        init_counter(dev, CNTR_ID_RETRIGGER, CNTR_CTRL_MODE_ONESHOT, 0);
        set_counter_value(dev, CNTR_ID_RETRIGGER, 0);

        /* init counter 1 to be retriggerable by counter 0 end count */
        init_counter(dev, CNTR_ID_WDOG, CNTR_CTRL_MODE_HWSIG,
                     CNTR_CTRL_TRIG_SRC_PREV_CNTR);
        set_counter_value(dev, CNTR_ID_WDOG, dev->timeout);

        /* enable counter 1 */
        counter_enable(dev, CNTR_ID_WDOG);

        /* start counter 1 by forcing immediate end count on counter 0 */
        counter_enable(dev, CNTR_ID_RETRIGGER);

        return 0;
}

static int armada_37xx_wdt_stop(struct watchdog_device *wdt)
{
        struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);

        counter_disable(dev, CNTR_ID_WDOG);
        counter_disable(dev, CNTR_ID_RETRIGGER);
        regmap_write(dev->cpu_misc, WDT_TIMER_SELECT, 0);

        return 0;
}

static const struct watchdog_info armada_37xx_wdt_info = {
        .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
        .identity = "Armada 37xx Watchdog",
};

static const struct watchdog_ops armada_37xx_wdt_ops = {
        .owner = THIS_MODULE,
        .start = armada_37xx_wdt_start,
        .stop = armada_37xx_wdt_stop,
        .ping = armada_37xx_wdt_ping,
        .set_timeout = armada_37xx_wdt_set_timeout,
        .get_timeleft = armada_37xx_wdt_get_timeleft,
};

static int armada_37xx_wdt_probe(struct platform_device *pdev)
{
        struct armada_37xx_watchdog *dev;
        struct regmap *regmap;
        int ret;

        dev = devm_kzalloc(&pdev->dev, sizeof(struct armada_37xx_watchdog),
                           GFP_KERNEL);
        if (!dev)
                return -ENOMEM;

        dev->wdt.info = &armada_37xx_wdt_info;
        dev->wdt.ops = &armada_37xx_wdt_ops;

        regmap = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
                                                 "marvell,system-controller");
        if (IS_ERR(regmap))
                return PTR_ERR(regmap);
        dev->cpu_misc = regmap;

        dev->reg = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(dev->reg))
                return PTR_ERR(dev->reg);

        /* init clock */
        dev->clk = devm_clk_get_enabled(&pdev->dev, NULL);
        if (IS_ERR(dev->clk))
                return PTR_ERR(dev->clk);

        dev->clk_rate = clk_get_rate(dev->clk);
        if (!dev->clk_rate)
                return -EINVAL;

        /*
         * Since the timeout in seconds is given as 32 bit unsigned int, and
         * the counters hold 64 bit values, even after multiplication by clock
         * rate the counter can hold timeout of UINT_MAX seconds.
         */
        dev->wdt.min_timeout = 1;
        dev->wdt.max_timeout = UINT_MAX;
        dev->wdt.parent = &pdev->dev;

        /* default value, possibly override by module parameter or dtb */
        dev->wdt.timeout = WATCHDOG_TIMEOUT;
        watchdog_init_timeout(&dev->wdt, timeout, &pdev->dev);

        platform_set_drvdata(pdev, &dev->wdt);
        watchdog_set_drvdata(&dev->wdt, dev);

        armada_37xx_wdt_set_timeout(&dev->wdt, dev->wdt.timeout);

        if (armada_37xx_wdt_is_running(dev))
                set_bit(WDOG_HW_RUNNING, &dev->wdt.status);

        watchdog_set_nowayout(&dev->wdt, nowayout);
        watchdog_stop_on_reboot(&dev->wdt);
        ret = devm_watchdog_register_device(&pdev->dev, &dev->wdt);
        if (ret)
                return ret;

        dev_info(&pdev->dev, "Initial timeout %d sec%s\n",
                 dev->wdt.timeout, nowayout ? ", nowayout" : "");

        return 0;
}

static int __maybe_unused armada_37xx_wdt_suspend(struct device *dev)
{
        struct watchdog_device *wdt = dev_get_drvdata(dev);

        return armada_37xx_wdt_stop(wdt);
}

static int __maybe_unused armada_37xx_wdt_resume(struct device *dev)
{
        struct watchdog_device *wdt = dev_get_drvdata(dev);

        if (watchdog_active(wdt))
                return armada_37xx_wdt_start(wdt);

        return 0;
}

static const struct dev_pm_ops armada_37xx_wdt_dev_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(armada_37xx_wdt_suspend,
                                armada_37xx_wdt_resume)
};

#ifdef CONFIG_OF
static const struct of_device_id armada_37xx_wdt_match[] = {
        { .compatible = "marvell,armada-3700-wdt", },
        {},
};
MODULE_DEVICE_TABLE(of, armada_37xx_wdt_match);
#endif

static struct platform_driver armada_37xx_wdt_driver = {
        .probe          = armada_37xx_wdt_probe,
        .driver         = {
                .name   = "armada_37xx_wdt",
                .of_match_table = of_match_ptr(armada_37xx_wdt_match),
                .pm = &armada_37xx_wdt_dev_pm_ops,
        },
};

module_platform_driver(armada_37xx_wdt_driver);

MODULE_AUTHOR("Marek Behun <kabel@kernel.org>");
MODULE_DESCRIPTION("Armada 37xx CPU Watchdog");

MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:armada_37xx_wdt");