// SPDX-License-Identifier: GPL-2.0-only
/*
 * drivers/watchdog/m54xx_wdt.c
 *
 * Watchdog driver for ColdFire MCF547x & MCF548x processors
 * Copyright 2010 (c) Philippe De Muyter <phdm@macqel.be>
 *
 * Adapted from the IXP4xx watchdog driver, which carries these notices:
 *
 *  Author: Deepak Saxena <dsaxena@plexity.net>
 *
 *  Copyright 2004 (c) MontaVista, Software, Inc.
 *  Based on sa1100 driver, Copyright (C) 2000 Oleg Drokin <green@crimea.edu>
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

#include <asm/coldfire.h>
#include <asm/m54xxsim.h>
#include <asm/m54xxgpt.h>

static bool nowayout = WATCHDOG_NOWAYOUT;
static unsigned int heartbeat = 30;     /* (secs) Default is 0.5 minute */
static unsigned long wdt_status;

#define WDT_IN_USE              0
#define WDT_OK_TO_CLOSE         1

static void wdt_enable(void)
{
        unsigned int gms0;

        /* preserve GPIO usage, if any */
        gms0 = __raw_readl(MCF_GPT_GMS0);
        if (gms0 & MCF_GPT_GMS_TMS_GPIO)
                gms0 &= (MCF_GPT_GMS_TMS_GPIO | MCF_GPT_GMS_GPIO_MASK
                                                        | MCF_GPT_GMS_OD);
        else
                gms0 = MCF_GPT_GMS_TMS_GPIO | MCF_GPT_GMS_OD;
        __raw_writel(gms0, MCF_GPT_GMS0);
        __raw_writel(MCF_GPT_GCIR_PRE(heartbeat*(MCF_BUSCLK/0xffff)) |
                        MCF_GPT_GCIR_CNT(0xffff), MCF_GPT_GCIR0);
        gms0 |= MCF_GPT_GMS_OCPW(0xA5) | MCF_GPT_GMS_WDEN | MCF_GPT_GMS_CE;
        __raw_writel(gms0, MCF_GPT_GMS0);
}

static void wdt_disable(void)
{
        unsigned int gms0;

        /* disable watchdog */
        gms0 = __raw_readl(MCF_GPT_GMS0);
        gms0 &= ~(MCF_GPT_GMS_WDEN | MCF_GPT_GMS_CE);
        __raw_writel(gms0, MCF_GPT_GMS0);
}

static void wdt_keepalive(void)
{
        unsigned int gms0;

        gms0 = __raw_readl(MCF_GPT_GMS0);
        gms0 |= MCF_GPT_GMS_OCPW(0xA5);
        __raw_writel(gms0, MCF_GPT_GMS0);
}

static int m54xx_wdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(WDT_IN_USE, &wdt_status))
                return -EBUSY;

        clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
        wdt_enable();
        return stream_open(inode, file);
}

static ssize_t m54xx_wdt_write(struct file *file, const char *data,
                                                size_t len, loff_t *ppos)
{
        if (len) {
                if (!nowayout) {
                        size_t i;

                        clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

                        for (i = 0; i != len; i++) {
                                char c;

                                if (get_user(c, data + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        set_bit(WDT_OK_TO_CLOSE, &wdt_status);
                        }
                }
                wdt_keepalive();
        }
        return len;
}

static const struct watchdog_info ident = {
        .options        = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT |
                                WDIOF_KEEPALIVEPING,
        .identity       = "Coldfire M54xx Watchdog",
};

static long m54xx_wdt_ioctl(struct file *file, unsigned int cmd,
                                                         unsigned long arg)
{
        int ret = -ENOTTY;
        int time;

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

        case WDIOC_GETSTATUS:
                ret = put_user(0, (int *)arg);
                break;

        case WDIOC_GETBOOTSTATUS:
                ret = put_user(0, (int *)arg);
                break;

        case WDIOC_KEEPALIVE:
                wdt_keepalive();
                ret = 0;
                break;

        case WDIOC_SETTIMEOUT:
                ret = get_user(time, (int *)arg);
                if (ret)
                        break;

                if (time <= 0 || time > 30) {
                        ret = -EINVAL;
                        break;
                }

                heartbeat = time;
                wdt_enable();
                fallthrough;

        case WDIOC_GETTIMEOUT:
                ret = put_user(heartbeat, (int *)arg);
                break;
        }
        return ret;
}

static int m54xx_wdt_release(struct inode *inode, struct file *file)
{
        if (test_bit(WDT_OK_TO_CLOSE, &wdt_status))
                wdt_disable();
        else {
                pr_crit("Device closed unexpectedly - timer will not stop\n");
                wdt_keepalive();
        }
        clear_bit(WDT_IN_USE, &wdt_status);
        clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

        return 0;
}


static const struct file_operations m54xx_wdt_fops = {
        .owner          = THIS_MODULE,
        .write          = m54xx_wdt_write,
        .unlocked_ioctl = m54xx_wdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = m54xx_wdt_open,
        .release        = m54xx_wdt_release,
};

static struct miscdevice m54xx_wdt_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &m54xx_wdt_fops,
};

static int __init m54xx_wdt_init(void)
{
        if (!request_mem_region(MCF_GPT_GCIR0, 4, "Coldfire M54xx Watchdog")) {
                pr_warn("I/O region busy\n");
                return -EBUSY;
        }
        pr_info("driver is loaded\n");

        return misc_register(&m54xx_wdt_miscdev);
}

static void __exit m54xx_wdt_exit(void)
{
        misc_deregister(&m54xx_wdt_miscdev);
        release_mem_region(MCF_GPT_GCIR0, 4);
}

module_init(m54xx_wdt_init);
module_exit(m54xx_wdt_exit);

MODULE_AUTHOR("Philippe De Muyter <phdm@macqel.be>");
MODULE_DESCRIPTION("Coldfire M54xx Watchdog");

module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds (default 30s)");

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

MODULE_LICENSE("GPL");