// SPDX-License-Identifier: GPL-2.0+
/*
 *      Watchdog driver for the SA11x0/PXA2xx
 *
 *      (c) Copyright 2000 Oleg Drokin <green@crimea.edu>
 *          Based on SoftDog driver by Alan Cox <alan@lxorguk.ukuu.org.uk>
 *
 *      Neither Oleg Drokin nor iXcelerator.com admit liability nor provide
 *      warranty for any of this software. This material is provided
 *      "AS-IS" and at no charge.
 *
 *      (c) Copyright 2000           Oleg Drokin <green@crimea.edu>
 *
 *      27/11/2000 Initial release
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/clk.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/bitops.h>
#include <linux/uaccess.h>
#include <linux/timex.h>

#define REG_OSMR0       0x0000  /* OS timer Match Reg. 0 */
#define REG_OSMR1       0x0004  /* OS timer Match Reg. 1 */
#define REG_OSMR2       0x0008  /* OS timer Match Reg. 2 */
#define REG_OSMR3       0x000c  /* OS timer Match Reg. 3 */
#define REG_OSCR        0x0010  /* OS timer Counter Reg. */
#define REG_OSSR        0x0014  /* OS timer Status Reg. */
#define REG_OWER        0x0018  /* OS timer Watch-dog Enable Reg. */
#define REG_OIER        0x001C  /* OS timer Interrupt Enable Reg. */

#define OSSR_M3         (1 << 3)        /* Match status channel 3 */
#define OSSR_M2         (1 << 2)        /* Match status channel 2 */
#define OSSR_M1         (1 << 1)        /* Match status channel 1 */
#define OSSR_M0         (1 << 0)        /* Match status channel 0 */

#define OWER_WME        (1 << 0)        /* Watchdog Match Enable */

#define OIER_E3         (1 << 3)        /* Interrupt enable channel 3 */
#define OIER_E2         (1 << 2)        /* Interrupt enable channel 2 */
#define OIER_E1         (1 << 1)        /* Interrupt enable channel 1 */
#define OIER_E0         (1 << 0)        /* Interrupt enable channel 0 */

static unsigned long oscr_freq;
static unsigned long sa1100wdt_users;
static unsigned int pre_margin;
static int boot_status;
static void __iomem *reg_base;

static inline void sa1100_wr(u32 val, u32 offset)
{
        writel_relaxed(val, reg_base + offset);
}

static inline u32 sa1100_rd(u32 offset)
{
        return readl_relaxed(reg_base + offset);
}

/*
 *      Allow only one person to hold it open
 */
static int sa1100dog_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(1, &sa1100wdt_users))
                return -EBUSY;

        /* Activate SA1100 Watchdog timer */
        sa1100_wr(sa1100_rd(REG_OSCR) + pre_margin, REG_OSMR3);
        sa1100_wr(OSSR_M3, REG_OSSR);
        sa1100_wr(OWER_WME, REG_OWER);
        sa1100_wr(sa1100_rd(REG_OIER) | OIER_E3, REG_OIER);
        return stream_open(inode, file);
}

/*
 * The watchdog cannot be disabled.
 *
 * Previous comments suggested that turning off the interrupt by
 * clearing REG_OIER[E3] would prevent the watchdog timing out but this
 * does not appear to be true (at least on the PXA255).
 */
static int sa1100dog_release(struct inode *inode, struct file *file)
{
        pr_crit("Device closed - timer will not stop\n");
        clear_bit(1, &sa1100wdt_users);
        return 0;
}

static ssize_t sa1100dog_write(struct file *file, const char __user *data,
                                                size_t len, loff_t *ppos)
{
        if (len)
                /* Refresh OSMR3 timer. */
                sa1100_wr(sa1100_rd(REG_OSCR) + pre_margin, REG_OSMR3);
        return len;
}

static const struct watchdog_info ident = {
        .options        = WDIOF_CARDRESET | WDIOF_SETTIMEOUT
                                | WDIOF_KEEPALIVEPING,
        .identity       = "SA1100/PXA255 Watchdog",
        .firmware_version       = 1,
};

static long sa1100dog_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        int ret = -ENOTTY;
        int time;
        void __user *argp = (void __user *)arg;
        int __user *p = argp;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                ret = copy_to_user(argp, &ident,
                                   sizeof(ident)) ? -EFAULT : 0;
                break;

        case WDIOC_GETSTATUS:
                ret = put_user(0, p);
                break;

        case WDIOC_GETBOOTSTATUS:
                ret = put_user(boot_status, p);
                break;

        case WDIOC_KEEPALIVE:
                sa1100_wr(sa1100_rd(REG_OSCR) + pre_margin, REG_OSMR3);
                ret = 0;
                break;

        case WDIOC_SETTIMEOUT:
                ret = get_user(time, p);
                if (ret)
                        break;

                if (time <= 0 || (oscr_freq * (long long)time >= 0xffffffff)) {
                        ret = -EINVAL;
                        break;
                }

                pre_margin = oscr_freq * time;
                sa1100_wr(sa1100_rd(REG_OSCR) + pre_margin, REG_OSMR3);
                fallthrough;

        case WDIOC_GETTIMEOUT:
                ret = put_user(pre_margin / oscr_freq, p);
                break;
        }
        return ret;
}

static const struct file_operations sa1100dog_fops = {
        .owner          = THIS_MODULE,
        .write          = sa1100dog_write,
        .unlocked_ioctl = sa1100dog_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = sa1100dog_open,
        .release        = sa1100dog_release,
};

static struct miscdevice sa1100dog_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &sa1100dog_fops,
};

static int margin = 60;         /* (secs) Default is 1 minute */
static struct clk *clk;

static int sa1100dog_probe(struct platform_device *pdev)
{
        int ret;
        int *platform_data;
        struct resource *res;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res)
                return -ENXIO;
        reg_base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
        if (!reg_base)
                return -ENOMEM;

        clk = clk_get(NULL, "OSTIMER0");
        if (IS_ERR(clk)) {
                pr_err("SA1100/PXA2xx Watchdog Timer: clock not found: %d\n",
                       (int) PTR_ERR(clk));
                return PTR_ERR(clk);
        }

        ret = clk_prepare_enable(clk);
        if (ret) {
                pr_err("SA1100/PXA2xx Watchdog Timer: clock failed to prepare+enable: %d\n",
                       ret);
                goto err;
        }

        oscr_freq = clk_get_rate(clk);

        platform_data = pdev->dev.platform_data;
        if (platform_data && *platform_data)
                boot_status = WDIOF_CARDRESET;
        pre_margin = oscr_freq * margin;

        ret = misc_register(&sa1100dog_miscdev);
        if (ret == 0) {
                pr_info("SA1100/PXA2xx Watchdog Timer: timer margin %d sec\n",
                        margin);
                return 0;
        }

        clk_disable_unprepare(clk);
err:
        clk_put(clk);
        return ret;
}

static void sa1100dog_remove(struct platform_device *pdev)
{
        misc_deregister(&sa1100dog_miscdev);
        clk_disable_unprepare(clk);
        clk_put(clk);
}

static struct platform_driver sa1100dog_driver = {
        .driver.name = "sa1100_wdt",
        .probe = sa1100dog_probe,
        .remove = sa1100dog_remove,
};
module_platform_driver(sa1100dog_driver);

MODULE_AUTHOR("Oleg Drokin <green@crimea.edu>");
MODULE_DESCRIPTION("SA1100/PXA2xx Watchdog");

module_param(margin, int, 0);
MODULE_PARM_DESC(margin, "Watchdog margin in seconds (default 60s)");

MODULE_LICENSE("GPL");