// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      nv_tco 0.01:    TCO timer driver for NV chipsets
 *
 *      (c) Copyright 2005 Google Inc., All Rights Reserved.
 *
 *      Based off i8xx_tco.c:
 *      (c) Copyright 2000 kernel concepts <nils@kernelconcepts.de>, All Rights
 *      Reserved.
 *                              https://www.kernelconcepts.de
 *
 *      TCO timer driver for NV chipsets
 *      based on softdog.c by Alan Cox <alan@redhat.com>
 */

/*
 *      Includes, defines, variables, module parameters, ...
 */

#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/init.h>
#include <linux/fs.h>
#include <linux/pci.h>
#include <linux/ioport.h>
#include <linux/jiffies.h>
#include <linux/platform_device.h>
#include <linux/uaccess.h>
#include <linux/io.h>

#include "nv_tco.h"

/* Module and version information */
#define TCO_VERSION "0.01"
#define TCO_MODULE_NAME "NV_TCO"
#define TCO_DRIVER_NAME   TCO_MODULE_NAME ", v" TCO_VERSION

/* internal variables */
static unsigned int tcobase;
static DEFINE_SPINLOCK(tco_lock);       /* Guards the hardware */
static unsigned long timer_alive;
static char tco_expect_close;
static struct pci_dev *tco_pci;

/* the watchdog platform device */
static struct platform_device *nv_tco_platform_device;

/* module parameters */
#define WATCHDOG_HEARTBEAT 30   /* 30 sec default heartbeat (2<heartbeat<39) */
static int heartbeat = WATCHDOG_HEARTBEAT;  /* in seconds */
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (2<heartbeat<39, "
                            "default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");

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) ")");

/*
 * Some TCO specific functions
 */
static inline unsigned char seconds_to_ticks(int seconds)
{
        /* the internal timer is stored as ticks which decrement
         * every 0.6 seconds */
        return (seconds * 10) / 6;
}

static void tco_timer_start(void)
{
        u32 val;
        unsigned long flags;

        spin_lock_irqsave(&tco_lock, flags);
        val = inl(TCO_CNT(tcobase));
        val &= ~TCO_CNT_TCOHALT;
        outl(val, TCO_CNT(tcobase));
        spin_unlock_irqrestore(&tco_lock, flags);
}

static void tco_timer_stop(void)
{
        u32 val;
        unsigned long flags;

        spin_lock_irqsave(&tco_lock, flags);
        val = inl(TCO_CNT(tcobase));
        val |= TCO_CNT_TCOHALT;
        outl(val, TCO_CNT(tcobase));
        spin_unlock_irqrestore(&tco_lock, flags);
}

static void tco_timer_keepalive(void)
{
        unsigned long flags;

        spin_lock_irqsave(&tco_lock, flags);
        outb(0x01, TCO_RLD(tcobase));
        spin_unlock_irqrestore(&tco_lock, flags);
}

static int tco_timer_set_heartbeat(int t)
{
        int ret = 0;
        unsigned char tmrval;
        unsigned long flags;
        u8 val;

        /*
         * note seconds_to_ticks(t) > t, so if t > 0x3f, so is
         * tmrval=seconds_to_ticks(t).  Check that the count in seconds isn't
         * out of range on it's own (to avoid overflow in tmrval).
         */
        if (t < 0 || t > 0x3f)
                return -EINVAL;
        tmrval = seconds_to_ticks(t);

        /* "Values of 0h-3h are ignored and should not be attempted" */
        if (tmrval > 0x3f || tmrval < 0x04)
                return -EINVAL;

        /* Write new heartbeat to watchdog */
        spin_lock_irqsave(&tco_lock, flags);
        val = inb(TCO_TMR(tcobase));
        val &= 0xc0;
        val |= tmrval;
        outb(val, TCO_TMR(tcobase));
        val = inb(TCO_TMR(tcobase));

        if ((val & 0x3f) != tmrval)
                ret = -EINVAL;
        spin_unlock_irqrestore(&tco_lock, flags);

        if (ret)
                return ret;

        heartbeat = t;
        return 0;
}

/*
 *      /dev/watchdog handling
 */

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

        /* Reload and activate timer */
        tco_timer_keepalive();
        tco_timer_start();
        return stream_open(inode, file);
}

static int nv_tco_release(struct inode *inode, struct file *file)
{
        /* Shut off the timer */
        if (tco_expect_close == 42) {
                tco_timer_stop();
        } else {
                pr_crit("Unexpected close, not stopping watchdog!\n");
                tco_timer_keepalive();
        }
        clear_bit(0, &timer_alive);
        tco_expect_close = 0;
        return 0;
}

static ssize_t nv_tco_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...
                         */
                        tco_expect_close = 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')
                                        tco_expect_close = 42;
                        }
                }

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

static long nv_tco_ioctl(struct file *file, unsigned int cmd,
                         unsigned long arg)
{
        int new_options, retval = -EINVAL;
        int new_heartbeat;
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        static const struct watchdog_info ident = {
                .options =              WDIOF_SETTIMEOUT |
                                        WDIOF_KEEPALIVEPING |
                                        WDIOF_MAGICCLOSE,
                .firmware_version =     0,
                .identity =             TCO_MODULE_NAME,
        };

        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:
                if (get_user(new_options, p))
                        return -EFAULT;
                if (new_options & WDIOS_DISABLECARD) {
                        tco_timer_stop();
                        retval = 0;
                }
                if (new_options & WDIOS_ENABLECARD) {
                        tco_timer_keepalive();
                        tco_timer_start();
                        retval = 0;
                }
                return retval;
        case WDIOC_KEEPALIVE:
                tco_timer_keepalive();
                return 0;
        case WDIOC_SETTIMEOUT:
                if (get_user(new_heartbeat, p))
                        return -EFAULT;
                if (tco_timer_set_heartbeat(new_heartbeat))
                        return -EINVAL;
                tco_timer_keepalive();
                fallthrough;
        case WDIOC_GETTIMEOUT:
                return put_user(heartbeat, p);
        default:
                return -ENOTTY;
        }
}

/*
 *      Kernel Interfaces
 */

static const struct file_operations nv_tco_fops = {
        .owner =                THIS_MODULE,
        .llseek =               no_llseek,
        .write =                nv_tco_write,
        .unlocked_ioctl =       nv_tco_ioctl,
        .compat_ioctl =         compat_ptr_ioctl,
        .open =                 nv_tco_open,
        .release =              nv_tco_release,
};

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

/*
 * 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 tco_pci_tbl[] = {
        { PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_NFORCE_MCP51_SMBUS,
          PCI_ANY_ID, PCI_ANY_ID, },
        { PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_NFORCE_MCP55_SMBUS,
          PCI_ANY_ID, PCI_ANY_ID, },
        { PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_NFORCE_MCP78S_SMBUS,
          PCI_ANY_ID, PCI_ANY_ID, },
        { PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_NFORCE_MCP79_SMBUS,
          PCI_ANY_ID, PCI_ANY_ID, },
        { 0, },                 /* End of list */
};
MODULE_DEVICE_TABLE(pci, tco_pci_tbl);

/*
 *      Init & exit routines
 */

static unsigned char nv_tco_getdevice(void)
{
        struct pci_dev *dev = NULL;
        u32 val;

        /* Find the PCI device */
        for_each_pci_dev(dev) {
                if (pci_match_id(tco_pci_tbl, dev) != NULL) {
                        tco_pci = dev;
                        break;
                }
        }

        if (!tco_pci)
                return 0;

        /* Find the base io port */
        pci_read_config_dword(tco_pci, 0x64, &val);
        val &= 0xffff;
        if (val == 0x0001 || val == 0x0000) {
                /* Something is wrong here, bar isn't setup */
                pr_err("failed to get tcobase address\n");
                return 0;
        }
        val &= 0xff00;
        tcobase = val + 0x40;

        if (!request_region(tcobase, 0x10, "NV TCO")) {
                pr_err("I/O address 0x%04x already in use\n", tcobase);
                return 0;
        }

        /* Set a reasonable heartbeat before we stop the timer */
        tco_timer_set_heartbeat(30);

        /*
         * Stop the TCO before we change anything so we don't race with
         * a zeroed timer.
         */
        tco_timer_keepalive();
        tco_timer_stop();

        /* Disable SMI caused by TCO */
        if (!request_region(MCP51_SMI_EN(tcobase), 4, "NV TCO")) {
                pr_err("I/O address 0x%04x already in use\n",
                       MCP51_SMI_EN(tcobase));
                goto out;
        }
        val = inl(MCP51_SMI_EN(tcobase));
        val &= ~MCP51_SMI_EN_TCO;
        outl(val, MCP51_SMI_EN(tcobase));
        val = inl(MCP51_SMI_EN(tcobase));
        release_region(MCP51_SMI_EN(tcobase), 4);
        if (val & MCP51_SMI_EN_TCO) {
                pr_err("Could not disable SMI caused by TCO\n");
                goto out;
        }

        /* Check chipset's NO_REBOOT bit */
        pci_read_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, &val);
        val |= MCP51_SMBUS_SETUP_B_TCO_REBOOT;
        pci_write_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, val);
        pci_read_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, &val);
        if (!(val & MCP51_SMBUS_SETUP_B_TCO_REBOOT)) {
                pr_err("failed to reset NO_REBOOT flag, reboot disabled by hardware\n");
                goto out;
        }

        return 1;
out:
        release_region(tcobase, 0x10);
        return 0;
}

static int nv_tco_init(struct platform_device *dev)
{
        int ret;

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

        /* Check to see if last reboot was due to watchdog timeout */
        pr_info("Watchdog reboot %sdetected\n",
                inl(TCO_STS(tcobase)) & TCO_STS_TCO2TO_STS ? "" : "not ");

        /* Clear out the old status */
        outl(TCO_STS_RESET, TCO_STS(tcobase));

        /*
         * Check that the heartbeat value is within it's range.
         * If not, reset to the default.
         */
        if (tco_timer_set_heartbeat(heartbeat)) {
                heartbeat = WATCHDOG_HEARTBEAT;
                tco_timer_set_heartbeat(heartbeat);
                pr_info("heartbeat value must be 2<heartbeat<39, using %d\n",
                        heartbeat);
        }

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

        clear_bit(0, &timer_alive);

        tco_timer_stop();

        pr_info("initialized (0x%04x). heartbeat=%d sec (nowayout=%d)\n",
                tcobase, heartbeat, nowayout);

        return 0;

unreg_region:
        release_region(tcobase, 0x10);
        return ret;
}

static void nv_tco_cleanup(void)
{
        u32 val;

        /* Stop the timer before we leave */
        if (!nowayout)
                tco_timer_stop();

        /* Set the NO_REBOOT bit to prevent later reboots, just for sure */
        pci_read_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, &val);
        val &= ~MCP51_SMBUS_SETUP_B_TCO_REBOOT;
        pci_write_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, val);
        pci_read_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, &val);
        if (val & MCP51_SMBUS_SETUP_B_TCO_REBOOT) {
                pr_crit("Couldn't unset REBOOT bit.  Machine may soon reset\n");
        }

        /* Deregister */
        misc_deregister(&nv_tco_miscdev);
        release_region(tcobase, 0x10);
}

static int nv_tco_remove(struct platform_device *dev)
{
        if (tcobase)
                nv_tco_cleanup();

        return 0;
}

static void nv_tco_shutdown(struct platform_device *dev)
{
        u32 val;

        tco_timer_stop();

        /* Some BIOSes fail the POST (once) if the NO_REBOOT flag is not
         * unset during shutdown. */
        pci_read_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, &val);
        val &= ~MCP51_SMBUS_SETUP_B_TCO_REBOOT;
        pci_write_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, val);
}

static struct platform_driver nv_tco_driver = {
        .probe          = nv_tco_init,
        .remove         = nv_tco_remove,
        .shutdown       = nv_tco_shutdown,
        .driver         = {
                .name   = TCO_MODULE_NAME,
        },
};

static int __init nv_tco_init_module(void)
{
        int err;

        pr_info("NV TCO WatchDog Timer Driver v%s\n", TCO_VERSION);

        err = platform_driver_register(&nv_tco_driver);
        if (err)
                return err;

        nv_tco_platform_device = platform_device_register_simple(
                                        TCO_MODULE_NAME, -1, NULL, 0);
        if (IS_ERR(nv_tco_platform_device)) {
                err = PTR_ERR(nv_tco_platform_device);
                goto unreg_platform_driver;
        }

        return 0;

unreg_platform_driver:
        platform_driver_unregister(&nv_tco_driver);
        return err;
}

static void __exit nv_tco_cleanup_module(void)
{
        platform_device_unregister(nv_tco_platform_device);
        platform_driver_unregister(&nv_tco_driver);
        pr_info("NV TCO Watchdog Module Unloaded\n");
}

module_init(nv_tco_init_module);
module_exit(nv_tco_cleanup_module);

MODULE_AUTHOR("Mike Waychison");
MODULE_DESCRIPTION("TCO timer driver for NV chipsets");
MODULE_LICENSE("GPL");