// SPDX-License-Identifier: GPL-2.0-only
/*
 *      Intel Atom E6xx Watchdog driver
 *
 *      Copyright (C) 2011 Alexander Stein
 *                <alexander.stein@systec-electronic.com>
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/watchdog.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/spinlock.h>

#define DRIVER_NAME "ie6xx_wdt"

#define PV1     0x00
#define PV2     0x04

#define RR0     0x0c
#define RR1     0x0d
#define WDT_RELOAD      0x01
#define WDT_TOUT        0x02

#define WDTCR   0x10
#define WDT_PRE_SEL     0x04
#define WDT_RESET_SEL   0x08
#define WDT_RESET_EN    0x10
#define WDT_TOUT_EN     0x20

#define DCR     0x14

#define WDTLR   0x18
#define WDT_LOCK        0x01
#define WDT_ENABLE      0x02
#define WDT_TOUT_CNF    0x03

#define MIN_TIME        1
#define MAX_TIME        (10 * 60) /* 10 minutes */
#define DEFAULT_TIME    60

static unsigned int timeout = DEFAULT_TIME;
module_param(timeout, uint, 0);
MODULE_PARM_DESC(timeout,
                "Default Watchdog timer setting ("
                __MODULE_STRING(DEFAULT_TIME) "s)."
                "The range is from 1 to 600");

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) ")");

static u8 resetmode = 0x10;
module_param(resetmode, byte, 0);
MODULE_PARM_DESC(resetmode,
        "Resetmode bits: 0x08 warm reset (cold reset otherwise), "
        "0x10 reset enable, 0x20 disable toggle GPIO[4] (default=0x10)");

static struct {
        unsigned short sch_wdtba;
        spinlock_t unlock_sequence;
#ifdef CONFIG_DEBUG_FS
        struct dentry *debugfs;
#endif
} ie6xx_wdt_data;

/*
 * This is needed to write to preload and reload registers
 * struct ie6xx_wdt_data.unlock_sequence must be used
 * to prevent sequence interrupts
 */
static void ie6xx_wdt_unlock_registers(void)
{
        outb(0x80, ie6xx_wdt_data.sch_wdtba + RR0);
        outb(0x86, ie6xx_wdt_data.sch_wdtba + RR0);
}

static int ie6xx_wdt_ping(struct watchdog_device *wdd)
{
        spin_lock(&ie6xx_wdt_data.unlock_sequence);
        ie6xx_wdt_unlock_registers();
        outb(WDT_RELOAD, ie6xx_wdt_data.sch_wdtba + RR1);
        spin_unlock(&ie6xx_wdt_data.unlock_sequence);
        return 0;
}

static int ie6xx_wdt_set_timeout(struct watchdog_device *wdd, unsigned int t)
{
        u32 preload;
        u64 clock;
        u8 wdtcr;

        /* Watchdog clock is PCI Clock (33MHz) */
        clock = 33000000;
        /* and the preload value is loaded into [34:15] of the down counter */
        preload = (t * clock) >> 15;
        /*
         * Manual states preload must be one less.
         * Does not wrap as t is at least 1
         */
        preload -= 1;

        spin_lock(&ie6xx_wdt_data.unlock_sequence);

        /* Set ResetMode & Enable prescaler for range 10ms to 10 min */
        wdtcr = resetmode & 0x38;
        outb(wdtcr, ie6xx_wdt_data.sch_wdtba + WDTCR);

        ie6xx_wdt_unlock_registers();
        outl(0, ie6xx_wdt_data.sch_wdtba + PV1);

        ie6xx_wdt_unlock_registers();
        outl(preload, ie6xx_wdt_data.sch_wdtba + PV2);

        ie6xx_wdt_unlock_registers();
        outb(WDT_RELOAD | WDT_TOUT, ie6xx_wdt_data.sch_wdtba + RR1);

        spin_unlock(&ie6xx_wdt_data.unlock_sequence);

        wdd->timeout = t;
        return 0;
}

static int ie6xx_wdt_start(struct watchdog_device *wdd)
{
        ie6xx_wdt_set_timeout(wdd, wdd->timeout);

        /* Enable the watchdog timer */
        spin_lock(&ie6xx_wdt_data.unlock_sequence);
        outb(WDT_ENABLE, ie6xx_wdt_data.sch_wdtba + WDTLR);
        spin_unlock(&ie6xx_wdt_data.unlock_sequence);

        return 0;
}

static int ie6xx_wdt_stop(struct watchdog_device *wdd)
{
        if (inb(ie6xx_wdt_data.sch_wdtba + WDTLR) & WDT_LOCK)
                return -1;

        /* Disable the watchdog timer */
        spin_lock(&ie6xx_wdt_data.unlock_sequence);
        outb(0, ie6xx_wdt_data.sch_wdtba + WDTLR);
        spin_unlock(&ie6xx_wdt_data.unlock_sequence);

        return 0;
}

static const struct watchdog_info ie6xx_wdt_info = {
        .identity =     "Intel Atom E6xx Watchdog",
        .options =      WDIOF_SETTIMEOUT |
                        WDIOF_MAGICCLOSE |
                        WDIOF_KEEPALIVEPING,
};

static const struct watchdog_ops ie6xx_wdt_ops = {
        .owner =        THIS_MODULE,
        .start =        ie6xx_wdt_start,
        .stop =         ie6xx_wdt_stop,
        .ping =         ie6xx_wdt_ping,
        .set_timeout =  ie6xx_wdt_set_timeout,
};

static struct watchdog_device ie6xx_wdt_dev = {
        .info =         &ie6xx_wdt_info,
        .ops =          &ie6xx_wdt_ops,
        .min_timeout =  MIN_TIME,
        .max_timeout =  MAX_TIME,
};

#ifdef CONFIG_DEBUG_FS

static int ie6xx_wdt_show(struct seq_file *s, void *unused)
{
        seq_printf(s, "PV1   = 0x%08x\n",
                inl(ie6xx_wdt_data.sch_wdtba + PV1));
        seq_printf(s, "PV2   = 0x%08x\n",
                inl(ie6xx_wdt_data.sch_wdtba + PV2));
        seq_printf(s, "RR    = 0x%08x\n",
                inw(ie6xx_wdt_data.sch_wdtba + RR0));
        seq_printf(s, "WDTCR = 0x%08x\n",
                inw(ie6xx_wdt_data.sch_wdtba + WDTCR));
        seq_printf(s, "DCR   = 0x%08x\n",
                inl(ie6xx_wdt_data.sch_wdtba + DCR));
        seq_printf(s, "WDTLR = 0x%08x\n",
                inw(ie6xx_wdt_data.sch_wdtba + WDTLR));

        seq_printf(s, "\n");
        return 0;
}

DEFINE_SHOW_ATTRIBUTE(ie6xx_wdt);

static void ie6xx_wdt_debugfs_init(void)
{
        /* /sys/kernel/debug/ie6xx_wdt */
        ie6xx_wdt_data.debugfs = debugfs_create_file("ie6xx_wdt",
                S_IFREG | S_IRUGO, NULL, NULL, &ie6xx_wdt_fops);
}

static void ie6xx_wdt_debugfs_exit(void)
{
        debugfs_remove(ie6xx_wdt_data.debugfs);
}

#else
static void ie6xx_wdt_debugfs_init(void)
{
}

static void ie6xx_wdt_debugfs_exit(void)
{
}
#endif

static int ie6xx_wdt_probe(struct platform_device *pdev)
{
        struct resource *res;
        u8 wdtlr;
        int ret;

        res = platform_get_resource(pdev, IORESOURCE_IO, 0);
        if (!res)
                return -ENODEV;

        if (!request_region(res->start, resource_size(res), pdev->name)) {
                dev_err(&pdev->dev, "Watchdog region 0x%llx already in use!\n",
                        (u64)res->start);
                return -EBUSY;
        }

        ie6xx_wdt_data.sch_wdtba = res->start;
        dev_dbg(&pdev->dev, "WDT = 0x%X\n", ie6xx_wdt_data.sch_wdtba);

        ie6xx_wdt_dev.timeout = timeout;
        watchdog_set_nowayout(&ie6xx_wdt_dev, nowayout);
        ie6xx_wdt_dev.parent = &pdev->dev;

        spin_lock_init(&ie6xx_wdt_data.unlock_sequence);

        wdtlr = inb(ie6xx_wdt_data.sch_wdtba + WDTLR);
        if (wdtlr & WDT_LOCK)
                dev_warn(&pdev->dev,
                        "Watchdog Timer is Locked (Reg=0x%x)\n", wdtlr);

        ie6xx_wdt_debugfs_init();

        ret = watchdog_register_device(&ie6xx_wdt_dev);
        if (ret)
                goto misc_register_error;

        return 0;

misc_register_error:
        ie6xx_wdt_debugfs_exit();
        release_region(res->start, resource_size(res));
        ie6xx_wdt_data.sch_wdtba = 0;
        return ret;
}

static void ie6xx_wdt_remove(struct platform_device *pdev)
{
        struct resource *res;

        res = platform_get_resource(pdev, IORESOURCE_IO, 0);
        ie6xx_wdt_stop(NULL);
        watchdog_unregister_device(&ie6xx_wdt_dev);
        ie6xx_wdt_debugfs_exit();
        release_region(res->start, resource_size(res));
        ie6xx_wdt_data.sch_wdtba = 0;
}

static struct platform_driver ie6xx_wdt_driver = {
        .probe          = ie6xx_wdt_probe,
        .remove         = ie6xx_wdt_remove,
        .driver         = {
                .name   = DRIVER_NAME,
        },
};

static int __init ie6xx_wdt_init(void)
{
        /* Check boot parameters to verify that their initial values */
        /* are in range. */
        if ((timeout < MIN_TIME) ||
            (timeout > MAX_TIME)) {
                pr_err("Watchdog timer: value of timeout %d (dec) "
                  "is out of range from %d to %d (dec)\n",
                  timeout, MIN_TIME, MAX_TIME);
                return -EINVAL;
        }

        return platform_driver_register(&ie6xx_wdt_driver);
}

static void __exit ie6xx_wdt_exit(void)
{
        platform_driver_unregister(&ie6xx_wdt_driver);
}

late_initcall(ie6xx_wdt_init);
module_exit(ie6xx_wdt_exit);

MODULE_AUTHOR("Alexander Stein <alexander.stein@systec-electronic.com>");
MODULE_DESCRIPTION("Intel Atom E6xx Watchdog Device Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRIVER_NAME);