/*
 * Watchdog driver for Broadcom BCM2835
 *
 * "bcm2708_wdog" driver written by Luke Diamand that was obtained from
 * branch "rpi-3.6.y" of git://github.com/raspberrypi/linux.git was used
 * as a hardware reference for the Broadcom BCM2835 watchdog timer.
 *
 * Copyright (C) 2013 Lubomir Rintel <lkundrak@v3.sk>
 *
 * 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/types.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/watchdog.h>
#include <linux/platform_device.h>
#include <linux/of_address.h>
#include <linux/of_platform.h>

#define PM_RSTC                         0x1c
#define PM_RSTS                         0x20
#define PM_WDOG                         0x24

#define PM_PASSWORD                     0x5a000000

#define PM_WDOG_TIME_SET                0x000fffff
#define PM_RSTC_WRCFG_CLR               0xffffffcf
#define PM_RSTS_HADWRH_SET              0x00000040
#define PM_RSTC_WRCFG_SET               0x00000030
#define PM_RSTC_WRCFG_FULL_RESET        0x00000020
#define PM_RSTC_RESET                   0x00000102

/*
 * The Raspberry Pi firmware uses the RSTS register to know which partition
 * to boot from. The partition value is spread into bits 0, 2, 4, 6, 8, 10.
 * Partition 63 is a special partition used by the firmware to indicate halt.
 */
#define PM_RSTS_RASPBERRYPI_HALT        0x555

#define SECS_TO_WDOG_TICKS(x) ((x) << 16)
#define WDOG_TICKS_TO_SECS(x) ((x) >> 16)

struct bcm2835_wdt {
        void __iomem            *base;
        spinlock_t              lock;
};

static unsigned int heartbeat;
static bool nowayout = WATCHDOG_NOWAYOUT;

static bool bcm2835_wdt_is_running(struct bcm2835_wdt *wdt)
{
        uint32_t cur;

        cur = readl(wdt->base + PM_RSTC);

        return !!(cur & PM_RSTC_WRCFG_FULL_RESET);
}

static int bcm2835_wdt_start(struct watchdog_device *wdog)
{
        struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
        uint32_t cur;
        unsigned long flags;

        spin_lock_irqsave(&wdt->lock, flags);

        writel_relaxed(PM_PASSWORD | (SECS_TO_WDOG_TICKS(wdog->timeout) &
                                PM_WDOG_TIME_SET), wdt->base + PM_WDOG);
        cur = readl_relaxed(wdt->base + PM_RSTC);
        writel_relaxed(PM_PASSWORD | (cur & PM_RSTC_WRCFG_CLR) |
                  PM_RSTC_WRCFG_FULL_RESET, wdt->base + PM_RSTC);

        spin_unlock_irqrestore(&wdt->lock, flags);

        return 0;
}

static int bcm2835_wdt_stop(struct watchdog_device *wdog)
{
        struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);

        writel_relaxed(PM_PASSWORD | PM_RSTC_RESET, wdt->base + PM_RSTC);
        return 0;
}

static unsigned int bcm2835_wdt_get_timeleft(struct watchdog_device *wdog)
{
        struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);

        uint32_t ret = readl_relaxed(wdt->base + PM_WDOG);
        return WDOG_TICKS_TO_SECS(ret & PM_WDOG_TIME_SET);
}

static void __bcm2835_restart(struct bcm2835_wdt *wdt)
{
        u32 val;

        /* use a timeout of 10 ticks (~150us) */
        writel_relaxed(10 | PM_PASSWORD, wdt->base + PM_WDOG);
        val = readl_relaxed(wdt->base + PM_RSTC);
        val &= PM_RSTC_WRCFG_CLR;
        val |= PM_PASSWORD | PM_RSTC_WRCFG_FULL_RESET;
        writel_relaxed(val, wdt->base + PM_RSTC);

        /* No sleeping, possibly atomic. */
        mdelay(1);
}

static int bcm2835_restart(struct watchdog_device *wdog,
                           unsigned long action, void *data)
{
        struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);

        __bcm2835_restart(wdt);

        return 0;
}

static const struct watchdog_ops bcm2835_wdt_ops = {
        .owner =        THIS_MODULE,
        .start =        bcm2835_wdt_start,
        .stop =         bcm2835_wdt_stop,
        .get_timeleft = bcm2835_wdt_get_timeleft,
        .restart =      bcm2835_restart,
};

static const struct watchdog_info bcm2835_wdt_info = {
        .options =      WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
                        WDIOF_KEEPALIVEPING,
        .identity =     "Broadcom BCM2835 Watchdog timer",
};

static struct watchdog_device bcm2835_wdt_wdd = {
        .info =         &bcm2835_wdt_info,
        .ops =          &bcm2835_wdt_ops,
        .min_timeout =  1,
        .max_timeout =  WDOG_TICKS_TO_SECS(PM_WDOG_TIME_SET),
        .timeout =      WDOG_TICKS_TO_SECS(PM_WDOG_TIME_SET),
};

/*
 * We can't really power off, but if we do the normal reset scheme, and
 * indicate to bootcode.bin not to reboot, then most of the chip will be
 * powered off.
 */
static void bcm2835_power_off(void)
{
        struct device_node *np =
                of_find_compatible_node(NULL, NULL, "brcm,bcm2835-pm-wdt");
        struct platform_device *pdev = of_find_device_by_node(np);
        struct bcm2835_wdt *wdt = platform_get_drvdata(pdev);
        u32 val;

        /*
         * We set the watchdog hard reset bit here to distinguish this reset
         * from the normal (full) reset. bootcode.bin will not reboot after a
         * hard reset.
         */
        val = readl_relaxed(wdt->base + PM_RSTS);
        val |= PM_PASSWORD | PM_RSTS_RASPBERRYPI_HALT;
        writel_relaxed(val, wdt->base + PM_RSTS);

        /* Continue with normal reset mechanism */
        __bcm2835_restart(wdt);
}

static int bcm2835_wdt_probe(struct platform_device *pdev)
{
        struct resource *res;
        struct device *dev = &pdev->dev;
        struct bcm2835_wdt *wdt;
        int err;

        wdt = devm_kzalloc(dev, sizeof(struct bcm2835_wdt), GFP_KERNEL);
        if (!wdt)
                return -ENOMEM;
        platform_set_drvdata(pdev, wdt);

        spin_lock_init(&wdt->lock);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        wdt->base = devm_ioremap_resource(dev, res);
        if (IS_ERR(wdt->base))
                return PTR_ERR(wdt->base);

        watchdog_set_drvdata(&bcm2835_wdt_wdd, wdt);
        watchdog_init_timeout(&bcm2835_wdt_wdd, heartbeat, dev);
        watchdog_set_nowayout(&bcm2835_wdt_wdd, nowayout);
        bcm2835_wdt_wdd.parent = dev;
        if (bcm2835_wdt_is_running(wdt)) {
                /*
                 * The currently active timeout value (set by the
                 * bootloader) may be different from the module
                 * heartbeat parameter or the value in device
                 * tree. But we just need to set WDOG_HW_RUNNING,
                 * because then the framework will "immediately" ping
                 * the device, updating the timeout.
                 */
                set_bit(WDOG_HW_RUNNING, &bcm2835_wdt_wdd.status);
        }

        watchdog_set_restart_priority(&bcm2835_wdt_wdd, 128);

        watchdog_stop_on_reboot(&bcm2835_wdt_wdd);
        err = devm_watchdog_register_device(dev, &bcm2835_wdt_wdd);
        if (err) {
                dev_err(dev, "Failed to register watchdog device");
                return err;
        }

        if (pm_power_off == NULL)
                pm_power_off = bcm2835_power_off;

        dev_info(dev, "Broadcom BCM2835 watchdog timer");
        return 0;
}

static int bcm2835_wdt_remove(struct platform_device *pdev)
{
        if (pm_power_off == bcm2835_power_off)
                pm_power_off = NULL;

        return 0;
}

static const struct of_device_id bcm2835_wdt_of_match[] = {
        { .compatible = "brcm,bcm2835-pm-wdt", },
        {},
};
MODULE_DEVICE_TABLE(of, bcm2835_wdt_of_match);

static struct platform_driver bcm2835_wdt_driver = {
        .probe          = bcm2835_wdt_probe,
        .remove         = bcm2835_wdt_remove,
        .driver = {
                .name =         "bcm2835-wdt",
                .of_match_table = bcm2835_wdt_of_match,
        },
};
module_platform_driver(bcm2835_wdt_driver);

module_param(heartbeat, uint, 0);
MODULE_PARM_DESC(heartbeat, "Initial watchdog heartbeat in seconds");

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

MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
MODULE_DESCRIPTION("Driver for Broadcom BCM2835 watchdog timer");
MODULE_LICENSE("GPL");