// SPDX-License-Identifier: GPL-2.0-only
/*
 *      ALi M7101 PMU Computer Watchdog Timer driver
 *
 *      Based on w83877f_wdt.c by Scott Jennings <linuxdrivers@oro.net>
 *      and the Cobalt kernel WDT timer driver by Tim Hockin
 *                                            <thockin@cobaltnet.com>
 *
 *      (c)2002 Steve Hill <steve@navaho.co.uk>
 *
 *  This WDT driver is different from most other Linux WDT
 *  drivers in that the driver will ping the watchdog by itself,
 *  because this particular WDT has a very short timeout (1.6
 *  seconds) and it would be insane to count on any userspace
 *  daemon always getting scheduled within that time frame.
 *
 *  Additions:
 *   Aug 23, 2004 - Added use_gpio module parameter for use on revision a1d PMUs
 *                  found on very old cobalt hardware.
 *                  -- Mike Waychison <michael.waychison@sun.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/ioport.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/pci.h>
#include <linux/io.h>
#include <linux/uaccess.h>


#define WDT_ENABLE 0x9C
#define WDT_DISABLE 0x8C

#define ALI_7101_WDT    0x92
#define ALI_7101_GPIO   0x7D
#define ALI_7101_GPIO_O 0x7E
#define ALI_WDT_ARM     0x01

/*
 * We're going to use a 1 second timeout.
 * If we reset the watchdog every ~250ms we should be safe.  */

#define WDT_INTERVAL (HZ/4+1)

/*
 * We must not require too good response from the userspace daemon.
 * Here we require the userspace daemon to send us a heartbeat
 * char to /dev/watchdog every 30 seconds.
 */

#define WATCHDOG_TIMEOUT 30            /* 30 sec default timeout */
/* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
static int timeout = WATCHDOG_TIMEOUT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
                "Watchdog timeout in seconds. (1<=timeout<=3600, default="
                                __MODULE_STRING(WATCHDOG_TIMEOUT) ")");

static int use_gpio; /* Use the pic (for a1d revision alim7101) */
module_param(use_gpio, int, 0);
MODULE_PARM_DESC(use_gpio,
                "Use the gpio watchdog (required by old cobalt boards).");

static void wdt_timer_ping(struct timer_list *);
static DEFINE_TIMER(timer, wdt_timer_ping);
static unsigned long next_heartbeat;
static unsigned long wdt_is_open;
static char wdt_expect_close;
static struct pci_dev *alim7101_pmu;

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) ")");

/*
 *      Whack the dog
 */

static void wdt_timer_ping(struct timer_list *unused)
{
        /* If we got a heartbeat pulse within the WDT_US_INTERVAL
         * we agree to ping the WDT
         */
        char tmp;

        if (time_before(jiffies, next_heartbeat)) {
                /* Ping the WDT (this is actually a disarm/arm sequence) */
                pci_read_config_byte(alim7101_pmu, 0x92, &tmp);
                pci_write_config_byte(alim7101_pmu,
                                        ALI_7101_WDT, (tmp & ~ALI_WDT_ARM));
                pci_write_config_byte(alim7101_pmu,
                                        ALI_7101_WDT, (tmp | ALI_WDT_ARM));
                if (use_gpio) {
                        pci_read_config_byte(alim7101_pmu,
                                        ALI_7101_GPIO_O, &tmp);
                        pci_write_config_byte(alim7101_pmu,
                                        ALI_7101_GPIO_O, tmp | 0x20);
                        pci_write_config_byte(alim7101_pmu,
                                        ALI_7101_GPIO_O, tmp & ~0x20);
                }
        } else {
                pr_warn("Heartbeat lost! Will not ping the watchdog\n");
        }
        /* Re-set the timer interval */
        mod_timer(&timer, jiffies + WDT_INTERVAL);
}

/*
 * Utility routines
 */

static void wdt_change(int writeval)
{
        char tmp;

        pci_read_config_byte(alim7101_pmu, ALI_7101_WDT, &tmp);
        if (writeval == WDT_ENABLE) {
                pci_write_config_byte(alim7101_pmu,
                                        ALI_7101_WDT, (tmp | ALI_WDT_ARM));
                if (use_gpio) {
                        pci_read_config_byte(alim7101_pmu,
                                        ALI_7101_GPIO_O, &tmp);
                        pci_write_config_byte(alim7101_pmu,
                                        ALI_7101_GPIO_O, tmp & ~0x20);
                }

        } else {
                pci_write_config_byte(alim7101_pmu,
                                        ALI_7101_WDT, (tmp & ~ALI_WDT_ARM));
                if (use_gpio) {
                        pci_read_config_byte(alim7101_pmu,
                                        ALI_7101_GPIO_O, &tmp);
                        pci_write_config_byte(alim7101_pmu,
                                        ALI_7101_GPIO_O, tmp | 0x20);
                }
        }
}

static void wdt_startup(void)
{
        next_heartbeat = jiffies + (timeout * HZ);

        /* We must enable before we kick off the timer in case the timer
           occurs as we ping it */

        wdt_change(WDT_ENABLE);

        /* Start the timer */
        mod_timer(&timer, jiffies + WDT_INTERVAL);

        pr_info("Watchdog timer is now enabled\n");
}

static void wdt_turnoff(void)
{
        /* Stop the timer */
        timer_delete_sync(&timer);
        wdt_change(WDT_DISABLE);
        pr_info("Watchdog timer is now disabled...\n");
}

static void wdt_keepalive(void)
{
        /* user land ping */
        next_heartbeat = jiffies + (timeout * HZ);
}

/*
 * /dev/watchdog handling
 */

static ssize_t fop_write(struct file *file, const char __user *buf,
                                                size_t count, loff_t *ppos)
{
        /* See if we got the magic character 'V' and reload the timer */
        if (count) {
                if (!nowayout) {
                        size_t ofs;

                        /* note: just in case someone wrote the magic character
                         * five months ago... */
                        wdt_expect_close = 0;

                        /* now scan */
                        for (ofs = 0; ofs != count; ofs++) {
                                char c;
                                if (get_user(c, buf + ofs))
                                        return -EFAULT;
                                if (c == 'V')
                                        wdt_expect_close = 42;
                        }
                }
                /* someone wrote to us, we should restart timer */
                wdt_keepalive();
        }
        return count;
}

static int fop_open(struct inode *inode, struct file *file)
{
        /* Just in case we're already talking to someone... */
        if (test_and_set_bit(0, &wdt_is_open))
                return -EBUSY;
        /* Good, fire up the show */
        wdt_startup();
        return stream_open(inode, file);
}

static int fop_close(struct inode *inode, struct file *file)
{
        if (wdt_expect_close == 42)
                wdt_turnoff();
        else {
                /* wim: shouldn't there be a: timer_delete(&timer); */
                pr_crit("device file closed unexpectedly. Will not stop the WDT!\n");
        }
        clear_bit(0, &wdt_is_open);
        wdt_expect_close = 0;
        return 0;
}

static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        static const struct watchdog_info ident = {
                .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
                                                        | WDIOF_MAGICCLOSE,
                .firmware_version = 1,
                .identity = "ALiM7101",
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);
        case WDIOC_SETOPTIONS:
        {
                int new_options, retval = -EINVAL;

                if (get_user(new_options, p))
                        return -EFAULT;
                if (new_options & WDIOS_DISABLECARD) {
                        wdt_turnoff();
                        retval = 0;
                }
                if (new_options & WDIOS_ENABLECARD) {
                        wdt_startup();
                        retval = 0;
                }
                return retval;
        }
        case WDIOC_KEEPALIVE:
                wdt_keepalive();
                return 0;
        case WDIOC_SETTIMEOUT:
        {
                int new_timeout;

                if (get_user(new_timeout, p))
                        return -EFAULT;
                /* arbitrary upper limit */
                if (new_timeout < 1 || new_timeout > 3600)
                        return -EINVAL;
                timeout = new_timeout;
                wdt_keepalive();
        }
                fallthrough;
        case WDIOC_GETTIMEOUT:
                return put_user(timeout, p);
        default:
                return -ENOTTY;
        }
}

static const struct file_operations wdt_fops = {
        .owner          =       THIS_MODULE,
        .write          =       fop_write,
        .open           =       fop_open,
        .release        =       fop_close,
        .unlocked_ioctl =       fop_ioctl,
        .compat_ioctl   =       compat_ptr_ioctl,
};

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

static int wdt_restart_handle(struct notifier_block *this, unsigned long mode,
                              void *cmd)
{
        /*
         * Cobalt devices have no way of rebooting themselves other
         * than getting the watchdog to pull reset, so we restart the
         * watchdog on reboot with no heartbeat.
         */
        wdt_change(WDT_ENABLE);

        /* loop until the watchdog fires */
        while (true)
                ;

        return NOTIFY_DONE;
}

static struct notifier_block wdt_restart_handler = {
        .notifier_call = wdt_restart_handle,
        .priority = 128,
};

/*
 *      Notifier for system down
 */

static int wdt_notify_sys(struct notifier_block *this,
                                        unsigned long code, void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                wdt_turnoff();

        return NOTIFY_DONE;
}

/*
 *      The WDT needs to learn about soft shutdowns in order to
 *      turn the timebomb registers off.
 */

static struct notifier_block wdt_notifier = {
        .notifier_call = wdt_notify_sys,
};

static void __exit alim7101_wdt_unload(void)
{
        wdt_turnoff();
        /* Deregister */
        misc_deregister(&wdt_miscdev);
        unregister_reboot_notifier(&wdt_notifier);
        unregister_restart_handler(&wdt_restart_handler);
        pci_dev_put(alim7101_pmu);
}

static int __init alim7101_wdt_init(void)
{
        int rc = -EBUSY;
        struct pci_dev *ali1543_south;
        char tmp;

        pr_info("Steve Hill <steve@navaho.co.uk>\n");
        alim7101_pmu = pci_get_device(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M7101,
                NULL);
        if (!alim7101_pmu) {
                pr_info("ALi M7101 PMU not present - WDT not set\n");
                return -EBUSY;
        }

        /* Set the WDT in the PMU to 1 second */
        pci_write_config_byte(alim7101_pmu, ALI_7101_WDT, 0x02);

        ali1543_south = pci_get_device(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M1533,
                NULL);
        if (!ali1543_south) {
                pr_info("ALi 1543 South-Bridge not present - WDT not set\n");
                goto err_out;
        }
        pci_read_config_byte(ali1543_south, 0x5e, &tmp);
        pci_dev_put(ali1543_south);
        if ((tmp & 0x1e) == 0x00) {
                if (!use_gpio) {
                        pr_info("Detected old alim7101 revision 'a1d'.  If this is a cobalt board, set the 'use_gpio' module parameter.\n");
                        goto err_out;
                }
                nowayout = 1;
        } else if ((tmp & 0x1e) != 0x12 && (tmp & 0x1e) != 0x00) {
                pr_info("ALi 1543 South-Bridge does not have the correct revision number (???1001?) - WDT not set\n");
                goto err_out;
        }

        if (timeout < 1 || timeout > 3600) {
                /* arbitrary upper limit */
                timeout = WATCHDOG_TIMEOUT;
                pr_info("timeout value must be 1 <= x <= 3600, using %d\n",
                        timeout);
        }

        rc = register_reboot_notifier(&wdt_notifier);
        if (rc) {
                pr_err("cannot register reboot notifier (err=%d)\n", rc);
                goto err_out;
        }

        rc = register_restart_handler(&wdt_restart_handler);
        if (rc) {
                pr_err("cannot register restart handler (err=%d)\n", rc);
                goto err_out_reboot;
        }

        rc = misc_register(&wdt_miscdev);
        if (rc) {
                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                       wdt_miscdev.minor, rc);
                goto err_out_restart;
        }

        if (nowayout)
                __module_get(THIS_MODULE);

        pr_info("WDT driver for ALi M7101 initialised. timeout=%d sec (nowayout=%d)\n",
                timeout, nowayout);
        return 0;

err_out_restart:
        unregister_restart_handler(&wdt_restart_handler);
err_out_reboot:
        unregister_reboot_notifier(&wdt_notifier);
err_out:
        pci_dev_put(alim7101_pmu);
        return rc;
}

module_init(alim7101_wdt_init);
module_exit(alim7101_wdt_unload);

static const struct pci_device_id alim7101_pci_tbl[] __used = {
        { PCI_DEVICE(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M1533) },
        { PCI_DEVICE(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M7101) },
        { }
};

MODULE_DEVICE_TABLE(pci, alim7101_pci_tbl);

MODULE_AUTHOR("Steve Hill");
MODULE_DESCRIPTION("ALi M7101 PMU Computer Watchdog Timer driver");
MODULE_LICENSE("GPL");