// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2013 Broadcom Corporation
 *
 */

#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>

#define SECWDOG_CTRL_REG                0x00000000
#define SECWDOG_COUNT_REG               0x00000004

#define SECWDOG_RESERVED_MASK           0x1dffffff
#define SECWDOG_WD_LOAD_FLAG            0x10000000
#define SECWDOG_EN_MASK                 0x08000000
#define SECWDOG_SRSTEN_MASK             0x04000000
#define SECWDOG_RES_MASK                0x00f00000
#define SECWDOG_COUNT_MASK              0x000fffff

#define SECWDOG_MAX_COUNT               SECWDOG_COUNT_MASK
#define SECWDOG_CLKS_SHIFT              20
#define SECWDOG_MAX_RES                 15
#define SECWDOG_DEFAULT_RESOLUTION      4
#define SECWDOG_MAX_TRY                 1000

#define SECS_TO_TICKS(x, w)             ((x) << (w)->resolution)
#define TICKS_TO_SECS(x, w)             ((x) >> (w)->resolution)

#define BCM_KONA_WDT_NAME               "bcm_kona_wdt"

struct bcm_kona_wdt {
        void __iomem *base;
        /*
         * One watchdog tick is 1/(2^resolution) seconds. Resolution can take
         * the values 0-15, meaning one tick can be 1s to 30.52us. Our default
         * resolution of 4 means one tick is 62.5ms.
         *
         * The watchdog counter is 20 bits. Depending on resolution, the maximum
         * counter value of 0xfffff expires after about 12 days (resolution 0)
         * down to only 32s (resolution 15). The default resolution of 4 gives
         * us a maximum of about 18 hours and 12 minutes before the watchdog
         * times out.
         */
        int resolution;
        spinlock_t lock;
#ifdef CONFIG_BCM_KONA_WDT_DEBUG
        unsigned long busy_count;
        struct dentry *debugfs;
#endif
};

static int secure_register_read(struct bcm_kona_wdt *wdt, uint32_t offset)
{
        uint32_t val;
        unsigned count = 0;

        /*
         * If the WD_LOAD_FLAG is set, the watchdog counter field is being
         * updated in hardware. Once the WD timer is updated in hardware, it
         * gets cleared.
         */
        do {
                if (unlikely(count > 1))
                        udelay(5);
                val = readl_relaxed(wdt->base + offset);
                count++;
        } while ((val & SECWDOG_WD_LOAD_FLAG) && count < SECWDOG_MAX_TRY);

#ifdef CONFIG_BCM_KONA_WDT_DEBUG
        /* Remember the maximum number iterations due to WD_LOAD_FLAG */
        if (count > wdt->busy_count)
                wdt->busy_count = count;
#endif

        /* This is the only place we return a negative value. */
        if (val & SECWDOG_WD_LOAD_FLAG)
                return -ETIMEDOUT;

        /* We always mask out reserved bits. */
        val &= SECWDOG_RESERVED_MASK;

        return val;
}

#ifdef CONFIG_BCM_KONA_WDT_DEBUG

static int bcm_kona_show(struct seq_file *s, void *data)
{
        int ctl_val, cur_val;
        unsigned long flags;
        struct bcm_kona_wdt *wdt = s->private;

        if (!wdt) {
                seq_puts(s, "No device pointer\n");
                return 0;
        }

        spin_lock_irqsave(&wdt->lock, flags);
        ctl_val = secure_register_read(wdt, SECWDOG_CTRL_REG);
        cur_val = secure_register_read(wdt, SECWDOG_COUNT_REG);
        spin_unlock_irqrestore(&wdt->lock, flags);

        if (ctl_val < 0 || cur_val < 0) {
                seq_puts(s, "Error accessing hardware\n");
        } else {
                int ctl, cur, ctl_sec, cur_sec, res;

                ctl = ctl_val & SECWDOG_COUNT_MASK;
                res = (ctl_val & SECWDOG_RES_MASK) >> SECWDOG_CLKS_SHIFT;
                cur = cur_val & SECWDOG_COUNT_MASK;
                ctl_sec = TICKS_TO_SECS(ctl, wdt);
                cur_sec = TICKS_TO_SECS(cur, wdt);
                seq_printf(s,
                           "Resolution: %d / %d\n"
                           "Control: %d s / %d (%#x) ticks\n"
                           "Current: %d s / %d (%#x) ticks\n"
                           "Busy count: %lu\n",
                           res, wdt->resolution,
                           ctl_sec, ctl, ctl,
                           cur_sec, cur, cur,
                           wdt->busy_count);
        }

        return 0;
}

DEFINE_SHOW_ATTRIBUTE(bcm_kona);

static void bcm_kona_wdt_debug_init(struct platform_device *pdev)
{
        struct dentry *dir;
        struct bcm_kona_wdt *wdt = platform_get_drvdata(pdev);

        if (!wdt)
                return;

        wdt->debugfs = NULL;

        dir = debugfs_create_dir(BCM_KONA_WDT_NAME, NULL);

        debugfs_create_file("info", S_IFREG | S_IRUGO, dir, wdt,
                            &bcm_kona_fops);
        wdt->debugfs = dir;
}

static void bcm_kona_wdt_debug_exit(struct platform_device *pdev)
{
        struct bcm_kona_wdt *wdt = platform_get_drvdata(pdev);

        if (wdt)
                debugfs_remove_recursive(wdt->debugfs);
}

#else

static void bcm_kona_wdt_debug_init(struct platform_device *pdev) {}
static void bcm_kona_wdt_debug_exit(struct platform_device *pdev) {}

#endif /* CONFIG_BCM_KONA_WDT_DEBUG */

static int bcm_kona_wdt_ctrl_reg_modify(struct bcm_kona_wdt *wdt,
                                        unsigned mask, unsigned newval)
{
        int val;
        unsigned long flags;
        int ret = 0;

        spin_lock_irqsave(&wdt->lock, flags);

        val = secure_register_read(wdt, SECWDOG_CTRL_REG);
        if (val < 0) {
                ret = val;
        } else {
                val &= ~mask;
                val |= newval;
                writel_relaxed(val, wdt->base + SECWDOG_CTRL_REG);
        }

        spin_unlock_irqrestore(&wdt->lock, flags);

        return ret;
}

static int bcm_kona_wdt_set_resolution_reg(struct bcm_kona_wdt *wdt)
{
        if (wdt->resolution > SECWDOG_MAX_RES)
                return -EINVAL;

        return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_RES_MASK,
                                        wdt->resolution << SECWDOG_CLKS_SHIFT);
}

static int bcm_kona_wdt_set_timeout_reg(struct watchdog_device *wdog,
                                        unsigned watchdog_flags)
{
        struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);

        return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_COUNT_MASK,
                                        SECS_TO_TICKS(wdog->timeout, wdt) |
                                        watchdog_flags);
}

static int bcm_kona_wdt_set_timeout(struct watchdog_device *wdog,
        unsigned int t)
{
        wdog->timeout = t;
        return 0;
}

static unsigned int bcm_kona_wdt_get_timeleft(struct watchdog_device *wdog)
{
        struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
        int val;
        unsigned long flags;

        spin_lock_irqsave(&wdt->lock, flags);
        val = secure_register_read(wdt, SECWDOG_COUNT_REG);
        spin_unlock_irqrestore(&wdt->lock, flags);

        if (val < 0)
                return val;

        return TICKS_TO_SECS(val & SECWDOG_COUNT_MASK, wdt);
}

static int bcm_kona_wdt_start(struct watchdog_device *wdog)
{
        return bcm_kona_wdt_set_timeout_reg(wdog,
                                        SECWDOG_EN_MASK | SECWDOG_SRSTEN_MASK);
}

static int bcm_kona_wdt_stop(struct watchdog_device *wdog)
{
        struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);

        return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_EN_MASK |
                                            SECWDOG_SRSTEN_MASK, 0);
}

static const struct watchdog_ops bcm_kona_wdt_ops = {
        .owner =        THIS_MODULE,
        .start =        bcm_kona_wdt_start,
        .stop =         bcm_kona_wdt_stop,
        .set_timeout =  bcm_kona_wdt_set_timeout,
        .get_timeleft = bcm_kona_wdt_get_timeleft,
};

static const struct watchdog_info bcm_kona_wdt_info = {
        .options =      WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
                        WDIOF_KEEPALIVEPING,
        .identity =     "Broadcom Kona Watchdog Timer",
};

static struct watchdog_device bcm_kona_wdt_wdd = {
        .info =         &bcm_kona_wdt_info,
        .ops =          &bcm_kona_wdt_ops,
        .min_timeout =  1,
        .max_timeout =  SECWDOG_MAX_COUNT >> SECWDOG_DEFAULT_RESOLUTION,
        .timeout =      SECWDOG_MAX_COUNT >> SECWDOG_DEFAULT_RESOLUTION,
};

static int bcm_kona_wdt_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct bcm_kona_wdt *wdt;
        int ret;

        wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
        if (!wdt)
                return -ENOMEM;

        spin_lock_init(&wdt->lock);

        wdt->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(wdt->base))
                return PTR_ERR(wdt->base);

        wdt->resolution = SECWDOG_DEFAULT_RESOLUTION;
        ret = bcm_kona_wdt_set_resolution_reg(wdt);
        if (ret) {
                dev_err(dev, "Failed to set resolution (error: %d)", ret);
                return ret;
        }

        platform_set_drvdata(pdev, wdt);
        watchdog_set_drvdata(&bcm_kona_wdt_wdd, wdt);
        bcm_kona_wdt_wdd.parent = dev;

        ret = bcm_kona_wdt_set_timeout_reg(&bcm_kona_wdt_wdd, 0);
        if (ret) {
                dev_err(dev, "Failed set watchdog timeout");
                return ret;
        }

        watchdog_stop_on_reboot(&bcm_kona_wdt_wdd);
        watchdog_stop_on_unregister(&bcm_kona_wdt_wdd);
        ret = devm_watchdog_register_device(dev, &bcm_kona_wdt_wdd);
        if (ret)
                return ret;

        bcm_kona_wdt_debug_init(pdev);
        dev_dbg(dev, "Broadcom Kona Watchdog Timer");

        return 0;
}

static void bcm_kona_wdt_remove(struct platform_device *pdev)
{
        bcm_kona_wdt_debug_exit(pdev);
        dev_dbg(&pdev->dev, "Watchdog driver disabled");
}

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

static struct platform_driver bcm_kona_wdt_driver = {
        .driver = {
                        .name = BCM_KONA_WDT_NAME,
                        .of_match_table = bcm_kona_wdt_of_match,
                  },
        .probe = bcm_kona_wdt_probe,
        .remove = bcm_kona_wdt_remove,
};

module_platform_driver(bcm_kona_wdt_driver);

MODULE_ALIAS("platform:" BCM_KONA_WDT_NAME);
MODULE_AUTHOR("Markus Mayer <mmayer@broadcom.com>");
MODULE_DESCRIPTION("Broadcom Kona Watchdog Driver");
MODULE_LICENSE("GPL v2");