// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      Watchdog for the 7101 PMU version found in the ALi M1535 chipsets
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.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/uaccess.h>
#include <linux/io.h>

#define WATCHDOG_NAME "ALi_M1535"
#define WATCHDOG_TIMEOUT 60     /* 60 sec default timeout */

/* internal variables */
static unsigned long ali_is_open;
static char ali_expect_release;
static struct pci_dev *ali_pci;
static u32 ali_timeout_bits;            /* stores the computed timeout */
static DEFINE_SPINLOCK(ali_lock);       /* Guards the hardware */

/* module parameters */
static int timeout = WATCHDOG_TIMEOUT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
                "Watchdog timeout in seconds. (0 < timeout < 18000, default="
                                __MODULE_STRING(WATCHDOG_TIMEOUT) ")");

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) ")");

/*
 *      ali_start       -       start watchdog countdown
 *
 *      Starts the timer running providing the timer has a counter
 *      configuration set.
 */

static void ali_start(void)
{
        u32 val;

        spin_lock(&ali_lock);

        pci_read_config_dword(ali_pci, 0xCC, &val);
        val &= ~0x3F;   /* Mask count */
        val |= (1 << 25) | ali_timeout_bits;
        pci_write_config_dword(ali_pci, 0xCC, val);

        spin_unlock(&ali_lock);
}

/*
 *      ali_stop        -       stop the timer countdown
 *
 *      Stop the ALi watchdog countdown
 */

static void ali_stop(void)
{
        u32 val;

        spin_lock(&ali_lock);

        pci_read_config_dword(ali_pci, 0xCC, &val);
        val &= ~0x3F;           /* Mask count to zero (disabled) */
        val &= ~(1 << 25);      /* and for safety mask the reset enable */
        pci_write_config_dword(ali_pci, 0xCC, val);

        spin_unlock(&ali_lock);
}

/*
 *      ali_keepalive   -       send a keepalive to the watchdog
 *
 *      Send a keepalive to the timer (actually we restart the timer).
 */

static void ali_keepalive(void)
{
        ali_start();
}

/*
 *      ali_settimer    -       compute the timer reload value
 *      @t: time in seconds
 *
 *      Computes the timeout values needed
 */

static int ali_settimer(int t)
{
        if (t < 0)
                return -EINVAL;
        else if (t < 60)
                ali_timeout_bits = t|(1 << 6);
        else if (t < 3600)
                ali_timeout_bits = (t / 60)|(1 << 7);
        else if (t < 18000)
                ali_timeout_bits = (t / 300)|(1 << 6)|(1 << 7);
        else
                return -EINVAL;

        timeout = t;
        return 0;
}

/*
 *      /dev/watchdog handling
 */

/*
 *      ali_write       -       writes to ALi watchdog
 *      @file: file from VFS
 *      @data: user address of data
 *      @len: length of data
 *      @ppos: pointer to the file offset
 *
 *      Handle a write to the ALi watchdog. Writing to the file pings
 *      the watchdog and resets it. Writing the magic 'V' sequence allows
 *      the next close to turn off the watchdog.
 */

static ssize_t ali_write(struct file *file, const char __user *data,
                                                size_t len, loff_t *ppos)
{
        /* See if we got the magic character 'V' and reload the timer */
        if (len) {
                if (!nowayout) {
                        size_t i;

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

                        /* scan to see whether or not we got
                           the magic character */
                        for (i = 0; i != len; i++) {
                                char c;
                                if (get_user(c, data + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        ali_expect_release = 42;
                        }
                }

                /* someone wrote to us, we should reload the timer */
                ali_start();
        }
        return len;
}

/*
 *      ali_ioctl       -       handle watchdog ioctls
 *      @file: VFS file pointer
 *      @cmd: ioctl number
 *      @arg: arguments to the ioctl
 *
 *      Handle the watchdog ioctls supported by the ALi driver. Really
 *      we want an extension to enable irq ack monitoring and the like
 */

static long ali_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 =     0,
                .identity =             "ALi M1535 WatchDog Timer",
        };

        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) {
                        ali_stop();
                        retval = 0;
                }
                if (new_options & WDIOS_ENABLECARD) {
                        ali_start();
                        retval = 0;
                }
                return retval;
        }
        case WDIOC_KEEPALIVE:
                ali_keepalive();
                return 0;
        case WDIOC_SETTIMEOUT:
        {
                int new_timeout;
                if (get_user(new_timeout, p))
                        return -EFAULT;
                if (ali_settimer(new_timeout))
                        return -EINVAL;
                ali_keepalive();
        }
                fallthrough;
        case WDIOC_GETTIMEOUT:
                return put_user(timeout, p);
        default:
                return -ENOTTY;
        }
}

/*
 *      ali_open        -       handle open of ali watchdog
 *      @inode: inode from VFS
 *      @file: file from VFS
 *
 *      Open the ALi watchdog device. Ensure only one person opens it
 *      at a time. Also start the watchdog running.
 */

static int ali_open(struct inode *inode, struct file *file)
{
        /* /dev/watchdog can only be opened once */
        if (test_and_set_bit(0, &ali_is_open))
                return -EBUSY;

        /* Activate */
        ali_start();
        return stream_open(inode, file);
}

/*
 *      ali_release     -       close an ALi watchdog
 *      @inode: inode from VFS
 *      @file: file from VFS
 *
 *      Close the ALi watchdog device. Actual shutdown of the timer
 *      only occurs if the magic sequence has been set.
 */

static int ali_release(struct inode *inode, struct file *file)
{
        /*
         *      Shut off the timer.
         */
        if (ali_expect_release == 42)
                ali_stop();
        else {
                pr_crit("Unexpected close, not stopping watchdog!\n");
                ali_keepalive();
        }
        clear_bit(0, &ali_is_open);
        ali_expect_release = 0;
        return 0;
}

/*
 *      ali_notify_sys  -       System down notifier
 *
 *      Notifier for system down
 */


static int ali_notify_sys(struct notifier_block *this,
                                        unsigned long code, void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                ali_stop();             /* Turn the WDT off */
        return NOTIFY_DONE;
}

/*
 *      Data for PCI driver interface
 *
 *      This data only exists for exporting the supported
 *      PCI ids via MODULE_DEVICE_TABLE.  We do not actually
 *      register a pci_driver, because someone else might one day
 *      want to register another driver on the same PCI id.
 */

static const struct pci_device_id ali_pci_tbl[] __used = {
        { PCI_VENDOR_ID_AL, 0x1533, PCI_ANY_ID, PCI_ANY_ID,},
        { PCI_VENDOR_ID_AL, 0x1535, PCI_ANY_ID, PCI_ANY_ID,},
        { 0, },
};
MODULE_DEVICE_TABLE(pci, ali_pci_tbl);

/*
 *      ali_find_watchdog       -       find a 1535 and 7101
 *
 *      Scans the PCI hardware for a 1535 series bridge and matching 7101
 *      watchdog device. This may be overtight but it is better to be safe
 */

static int __init ali_find_watchdog(void)
{
        struct pci_dev *pdev;
        u32 wdog;

        /* Check for a 1533/1535 series bridge */
        pdev = pci_get_device(PCI_VENDOR_ID_AL, 0x1535, NULL);
        if (pdev == NULL)
                pdev = pci_get_device(PCI_VENDOR_ID_AL, 0x1533, NULL);
        if (pdev == NULL)
                return -ENODEV;
        pci_dev_put(pdev);

        /* Check for the a 7101 PMU */
        pdev = pci_get_device(PCI_VENDOR_ID_AL, 0x7101, NULL);
        if (pdev == NULL)
                return -ENODEV;

        if (pci_enable_device(pdev)) {
                pci_dev_put(pdev);
                return -EIO;
        }

        ali_pci = pdev;

        /*
         *      Initialize the timer bits
         */
        pci_read_config_dword(pdev, 0xCC, &wdog);

        /* Timer bits */
        wdog &= ~0x3F;
        /* Issued events */
        wdog &= ~((1 << 27)|(1 << 26)|(1 << 25)|(1 << 24));
        /* No monitor bits */
        wdog &= ~((1 << 16)|(1 << 13)|(1 << 12)|(1 << 11)|(1 << 10)|(1 << 9));

        pci_write_config_dword(pdev, 0xCC, wdog);

        return 0;
}

/*
 *      Kernel Interfaces
 */

static const struct file_operations ali_fops = {
        .owner          =       THIS_MODULE,
        .write          =       ali_write,
        .unlocked_ioctl =       ali_ioctl,
        .compat_ioctl   =       compat_ptr_ioctl,
        .open           =       ali_open,
        .release        =       ali_release,
};

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

static struct notifier_block ali_notifier = {
        .notifier_call =        ali_notify_sys,
};

/*
 *      watchdog_init   -       module initialiser
 *
 *      Scan for a suitable watchdog and if so initialize it. Return an error
 *      if we cannot, the error causes the module to unload
 */

static int __init watchdog_init(void)
{
        int ret;

        /* Check whether or not the hardware watchdog is there */
        if (ali_find_watchdog() != 0)
                return -ENODEV;

        /* Check that the timeout value is within it's range;
           if not reset to the default */
        if (timeout < 1 || timeout >= 18000) {
                timeout = WATCHDOG_TIMEOUT;
                pr_info("timeout value must be 0 < timeout < 18000, using %d\n",
                        timeout);
        }

        /* Calculate the watchdog's timeout */
        ali_settimer(timeout);

        ret = register_reboot_notifier(&ali_notifier);
        if (ret != 0) {
                pr_err("cannot register reboot notifier (err=%d)\n", ret);
                goto out;
        }

        ret = misc_register(&ali_miscdev);
        if (ret != 0) {
                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                       WATCHDOG_MINOR, ret);
                goto unreg_reboot;
        }

        pr_info("initialized. timeout=%d sec (nowayout=%d)\n",
                timeout, nowayout);

out:
        return ret;
unreg_reboot:
        unregister_reboot_notifier(&ali_notifier);
        goto out;
}

/*
 *      watchdog_exit   -       module de-initialiser
 *
 *      Called while unloading a successfully installed watchdog module.
 */

static void __exit watchdog_exit(void)
{
        /* Stop the timer before we leave */
        ali_stop();

        /* Deregister */
        misc_deregister(&ali_miscdev);
        unregister_reboot_notifier(&ali_notifier);
        pci_dev_put(ali_pci);
}

module_init(watchdog_init);
module_exit(watchdog_exit);

MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("ALi M1535 PMU Watchdog Timer driver");
MODULE_LICENSE("GPL");