// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * FIXME: add wdrtas_get_status and wdrtas_get_boot_status as soon as
 * RTAS calls are available
 */

/*
 * RTAS watchdog driver
 *
 * (C) Copyright IBM Corp. 2005
 * device driver to exploit watchdog RTAS functions
 *
 * Authors : Utz Bacher <utz.bacher@de.ibm.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/types.h>
#include <linux/watchdog.h>
#include <linux/uaccess.h>

#include <asm/rtas.h>

#define WDRTAS_MAGIC_CHAR               42
#define WDRTAS_SUPPORTED_MASK           (WDIOF_SETTIMEOUT | \
                                         WDIOF_MAGICCLOSE)

MODULE_AUTHOR("Utz Bacher <utz.bacher@de.ibm.com>");
MODULE_DESCRIPTION("RTAS watchdog driver");
MODULE_LICENSE("GPL");

static bool wdrtas_nowayout = WATCHDOG_NOWAYOUT;
static atomic_t wdrtas_miscdev_open = ATOMIC_INIT(0);
static char wdrtas_expect_close;

static int wdrtas_interval;

#define WDRTAS_THERMAL_SENSOR           3
static int wdrtas_token_get_sensor_state;
#define WDRTAS_SURVEILLANCE_IND         9000
static int wdrtas_token_set_indicator;
#define WDRTAS_SP_SPI                   28
static int wdrtas_token_get_sp;
static int wdrtas_token_event_scan;

#define WDRTAS_DEFAULT_INTERVAL         300

#define WDRTAS_LOGBUFFER_LEN            128
static char wdrtas_logbuffer[WDRTAS_LOGBUFFER_LEN];


/*** watchdog access functions */

/**
 * wdrtas_set_interval - sets the watchdog interval
 * @interval: new interval
 *
 * returns 0 on success, <0 on failures
 *
 * wdrtas_set_interval sets the watchdog keepalive interval by calling the
 * RTAS function set-indicator (surveillance). The unit of interval is
 * seconds.
 */

static int wdrtas_set_interval(int interval)
{
        long result;
        static int print_msg = 10;

        /* rtas uses minutes */
        interval = (interval + 59) / 60;

        result = rtas_call(wdrtas_token_set_indicator, 3, 1, NULL,
                           WDRTAS_SURVEILLANCE_IND, 0, interval);
        if (result < 0 && print_msg) {
                pr_err("setting the watchdog to %i timeout failed: %li\n",
                       interval, result);
                print_msg--;
        }

        return result;
}

#define WDRTAS_SP_SPI_LEN 4

/**
 * wdrtas_get_interval - returns the current watchdog interval
 * @fallback_value: value (in seconds) to use, if the RTAS call fails
 *
 * returns the interval
 *
 * wdrtas_get_interval returns the current watchdog keepalive interval
 * as reported by the RTAS function ibm,get-system-parameter. The unit
 * of the return value is seconds.
 */
static int wdrtas_get_interval(int fallback_value)
{
        long result;
        char value[WDRTAS_SP_SPI_LEN];

        spin_lock(&rtas_data_buf_lock);
        memset(rtas_data_buf, 0, WDRTAS_SP_SPI_LEN);
        result = rtas_call(wdrtas_token_get_sp, 3, 1, NULL,
                           WDRTAS_SP_SPI, __pa(rtas_data_buf),
                           WDRTAS_SP_SPI_LEN);

        memcpy(value, rtas_data_buf, WDRTAS_SP_SPI_LEN);
        spin_unlock(&rtas_data_buf_lock);

        if (value[0] != 0 || value[1] != 2 || value[3] != 0 || result < 0) {
                pr_warn("could not get sp_spi watchdog timeout (%li). Continuing\n",
                        result);
                return fallback_value;
        }

        /* rtas uses minutes */
        return ((int)value[2]) * 60;
}

/**
 * wdrtas_timer_start - starts watchdog
 *
 * wdrtas_timer_start starts the watchdog by calling the RTAS function
 * set-interval (surveillance)
 */
static void wdrtas_timer_start(void)
{
        wdrtas_set_interval(wdrtas_interval);
}

/**
 * wdrtas_timer_stop - stops watchdog
 *
 * wdrtas_timer_stop stops the watchdog timer by calling the RTAS function
 * set-interval (surveillance)
 */
static void wdrtas_timer_stop(void)
{
        wdrtas_set_interval(0);
}

/**
 * wdrtas_timer_keepalive - resets watchdog timer to keep system alive
 *
 * wdrtas_timer_keepalive restarts the watchdog timer by calling the
 * RTAS function event-scan and repeats these calls as long as there are
 * events available. All events will be dumped.
 */
static void wdrtas_timer_keepalive(void)
{
        long result;

        do {
                result = rtas_call(wdrtas_token_event_scan, 4, 1, NULL,
                                   RTAS_EVENT_SCAN_ALL_EVENTS, 0,
                                   (void *)__pa(wdrtas_logbuffer),
                                   WDRTAS_LOGBUFFER_LEN);
                if (result < 0)
                        pr_err("event-scan failed: %li\n", result);
                if (result == 0)
                        print_hex_dump(KERN_INFO, "dumping event, data: ",
                                DUMP_PREFIX_OFFSET, 16, 1,
                                wdrtas_logbuffer, WDRTAS_LOGBUFFER_LEN, false);
        } while (result == 0);
}

/**
 * wdrtas_get_temperature - returns current temperature
 *
 * returns temperature or <0 on failures
 *
 * wdrtas_get_temperature returns the current temperature in Fahrenheit. It
 * uses the RTAS call get-sensor-state, token 3 to do so
 */
static int wdrtas_get_temperature(void)
{
        int result;
        int temperature = 0;

        result = rtas_get_sensor(WDRTAS_THERMAL_SENSOR, 0, &temperature);

        if (result < 0)
                pr_warn("reading the thermal sensor failed: %i\n", result);
        else
                temperature = ((temperature * 9) / 5) + 32; /* fahrenheit */

        return temperature;
}

/**
 * wdrtas_get_status - returns the status of the watchdog
 *
 * returns a bitmask of defines WDIOF_... as defined in
 * include/linux/watchdog.h
 */
static int wdrtas_get_status(void)
{
        return 0; /* TODO */
}

/**
 * wdrtas_get_boot_status - returns the reason for the last boot
 *
 * returns a bitmask of defines WDIOF_... as defined in
 * include/linux/watchdog.h, indicating why the watchdog rebooted the system
 */
static int wdrtas_get_boot_status(void)
{
        return 0; /* TODO */
}

/*** watchdog API and operations stuff */

/* wdrtas_write - called when watchdog device is written to
 * @file: file structure
 * @buf: user buffer with data
 * @len: amount to data written
 * @ppos: position in file
 *
 * returns the number of successfully processed characters, which is always
 * the number of bytes passed to this function
 *
 * wdrtas_write processes all the data given to it and looks for the magic
 * character 'V'. This character allows the watchdog device to be closed
 * properly.
 */
static ssize_t wdrtas_write(struct file *file, const char __user *buf,
             size_t len, loff_t *ppos)
{
        int i;
        char c;

        if (!len)
                goto out;

        if (!wdrtas_nowayout) {
                wdrtas_expect_close = 0;
                /* look for 'V' */
                for (i = 0; i < len; i++) {
                        if (get_user(c, buf + i))
                                return -EFAULT;
                        /* allow to close device */
                        if (c == 'V')
                                wdrtas_expect_close = WDRTAS_MAGIC_CHAR;
                }
        }

        wdrtas_timer_keepalive();

out:
        return len;
}

/**
 * wdrtas_ioctl - ioctl function for the watchdog device
 * @file: file structure
 * @cmd: command for ioctl
 * @arg: argument pointer
 *
 * returns 0 on success, <0 on failure
 *
 * wdrtas_ioctl implements the watchdog API ioctls
 */

static long wdrtas_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        int __user *argp = (void __user *)arg;
        int i;
        static const struct watchdog_info wdinfo = {
                .options = WDRTAS_SUPPORTED_MASK,
                .firmware_version = 0,
                .identity = "wdrtas",
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                if (copy_to_user(argp, &wdinfo, sizeof(wdinfo)))
                        return -EFAULT;
                return 0;

        case WDIOC_GETSTATUS:
                i = wdrtas_get_status();
                return put_user(i, argp);

        case WDIOC_GETBOOTSTATUS:
                i = wdrtas_get_boot_status();
                return put_user(i, argp);

        case WDIOC_GETTEMP:
                if (wdrtas_token_get_sensor_state == RTAS_UNKNOWN_SERVICE)
                        return -EOPNOTSUPP;

                i = wdrtas_get_temperature();
                return put_user(i, argp);

        case WDIOC_SETOPTIONS:
                if (get_user(i, argp))
                        return -EFAULT;
                if (i & WDIOS_DISABLECARD)
                        wdrtas_timer_stop();
                if (i & WDIOS_ENABLECARD) {
                        wdrtas_timer_keepalive();
                        wdrtas_timer_start();
                }
                /* not implemented. Done by H8
                if (i & WDIOS_TEMPPANIC) {
                } */
                return 0;

        case WDIOC_KEEPALIVE:
                wdrtas_timer_keepalive();
                return 0;

        case WDIOC_SETTIMEOUT:
                if (get_user(i, argp))
                        return -EFAULT;

                if (wdrtas_set_interval(i))
                        return -EINVAL;

                wdrtas_timer_keepalive();

                if (wdrtas_token_get_sp == RTAS_UNKNOWN_SERVICE)
                        wdrtas_interval = i;
                else
                        wdrtas_interval = wdrtas_get_interval(i);
                fallthrough;

        case WDIOC_GETTIMEOUT:
                return put_user(wdrtas_interval, argp);

        default:
                return -ENOTTY;
        }
}

/**
 * wdrtas_open - open function of watchdog device
 * @inode: inode structure
 * @file: file structure
 *
 * returns 0 on success, -EBUSY if the file has been opened already, <0 on
 * other failures
 *
 * function called when watchdog device is opened
 */
static int wdrtas_open(struct inode *inode, struct file *file)
{
        /* only open once */
        if (atomic_inc_return(&wdrtas_miscdev_open) > 1) {
                atomic_dec(&wdrtas_miscdev_open);
                return -EBUSY;
        }

        wdrtas_timer_start();
        wdrtas_timer_keepalive();

        return stream_open(inode, file);
}

/**
 * wdrtas_close - close function of watchdog device
 * @inode: inode structure
 * @file: file structure
 *
 * returns 0 on success
 *
 * close function. Always succeeds
 */
static int wdrtas_close(struct inode *inode, struct file *file)
{
        /* only stop watchdog, if this was announced using 'V' before */
        if (wdrtas_expect_close == WDRTAS_MAGIC_CHAR)
                wdrtas_timer_stop();
        else {
                pr_warn("got unexpected close. Watchdog not stopped.\n");
                wdrtas_timer_keepalive();
        }

        wdrtas_expect_close = 0;
        atomic_dec(&wdrtas_miscdev_open);
        return 0;
}

/**
 * wdrtas_temp_read - gives back the temperature in fahrenheit
 * @file: file structure
 * @buf: user buffer
 * @count: number of bytes to be read
 * @ppos: position in file
 *
 * returns always 1 or -EFAULT in case of user space copy failures, <0 on
 * other failures
 *
 * wdrtas_temp_read gives the temperature to the users by copying this
 * value as one byte into the user space buffer. The unit is Fahrenheit...
 */
static ssize_t wdrtas_temp_read(struct file *file, char __user *buf,
                 size_t count, loff_t *ppos)
{
        int temperature = 0;

        temperature = wdrtas_get_temperature();
        if (temperature < 0)
                return temperature;

        if (copy_to_user(buf, &temperature, 1))
                return -EFAULT;

        return 1;
}

/**
 * wdrtas_temp_open - open function of temperature device
 * @inode: inode structure
 * @file: file structure
 *
 * returns 0 on success, <0 on failure
 *
 * function called when temperature device is opened
 */
static int wdrtas_temp_open(struct inode *inode, struct file *file)
{
        return stream_open(inode, file);
}

/**
 * wdrtas_temp_close - close function of temperature device
 * @inode: inode structure
 * @file: file structure
 *
 * returns 0 on success
 *
 * close function. Always succeeds
 */
static int wdrtas_temp_close(struct inode *inode, struct file *file)
{
        return 0;
}

/**
 * wdrtas_reboot - reboot notifier function
 * @nb: notifier block structure
 * @code: reboot code
 * @ptr: unused
 *
 * returns NOTIFY_DONE
 *
 * wdrtas_reboot stops the watchdog in case of a reboot
 */
static int wdrtas_reboot(struct notifier_block *this,
                                        unsigned long code, void *ptr)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                wdrtas_timer_stop();

        return NOTIFY_DONE;
}

/*** initialization stuff */

static const struct file_operations wdrtas_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = wdrtas_write,
        .unlocked_ioctl = wdrtas_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = wdrtas_open,
        .release        = wdrtas_close,
};

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

static const struct file_operations wdrtas_temp_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .read           = wdrtas_temp_read,
        .open           = wdrtas_temp_open,
        .release        = wdrtas_temp_close,
};

static struct miscdevice wdrtas_tempdev = {
        .minor =        TEMP_MINOR,
        .name =         "temperature",
        .fops =         &wdrtas_temp_fops,
};

static struct notifier_block wdrtas_notifier = {
        .notifier_call =        wdrtas_reboot,
};

/**
 * wdrtas_get_tokens - reads in RTAS tokens
 *
 * returns 0 on success, <0 on failure
 *
 * wdrtas_get_tokens reads in the tokens for the RTAS calls used in
 * this watchdog driver. It tolerates, if "get-sensor-state" and
 * "ibm,get-system-parameter" are not available.
 */
static int wdrtas_get_tokens(void)
{
        wdrtas_token_get_sensor_state = rtas_token("get-sensor-state");
        if (wdrtas_token_get_sensor_state == RTAS_UNKNOWN_SERVICE) {
                pr_warn("couldn't get token for get-sensor-state. Trying to continue without temperature support.\n");
        }

        wdrtas_token_get_sp = rtas_token("ibm,get-system-parameter");
        if (wdrtas_token_get_sp == RTAS_UNKNOWN_SERVICE) {
                pr_warn("couldn't get token for ibm,get-system-parameter. Trying to continue with a default timeout value of %i seconds.\n",
                        WDRTAS_DEFAULT_INTERVAL);
        }

        wdrtas_token_set_indicator = rtas_token("set-indicator");
        if (wdrtas_token_set_indicator == RTAS_UNKNOWN_SERVICE) {
                pr_err("couldn't get token for set-indicator. Terminating watchdog code.\n");
                return -EIO;
        }

        wdrtas_token_event_scan = rtas_token("event-scan");
        if (wdrtas_token_event_scan == RTAS_UNKNOWN_SERVICE) {
                pr_err("couldn't get token for event-scan. Terminating watchdog code.\n");
                return -EIO;
        }

        return 0;
}

/**
 * wdrtas_unregister_devs - unregisters the misc dev handlers
 *
 * wdrtas_register_devs unregisters the watchdog and temperature watchdog
 * misc devs
 */
static void wdrtas_unregister_devs(void)
{
        misc_deregister(&wdrtas_miscdev);
        if (wdrtas_token_get_sensor_state != RTAS_UNKNOWN_SERVICE)
                misc_deregister(&wdrtas_tempdev);
}

/**
 * wdrtas_register_devs - registers the misc dev handlers
 *
 * returns 0 on success, <0 on failure
 *
 * wdrtas_register_devs registers the watchdog and temperature watchdog
 * misc devs
 */
static int wdrtas_register_devs(void)
{
        int result;

        result = misc_register(&wdrtas_miscdev);
        if (result) {
                pr_err("couldn't register watchdog misc device. Terminating watchdog code.\n");
                return result;
        }

        if (wdrtas_token_get_sensor_state != RTAS_UNKNOWN_SERVICE) {
                result = misc_register(&wdrtas_tempdev);
                if (result) {
                        pr_warn("couldn't register watchdog temperature misc device. Continuing without temperature support.\n");
                        wdrtas_token_get_sensor_state = RTAS_UNKNOWN_SERVICE;
                }
        }

        return 0;
}

/**
 * wdrtas_init - init function of the watchdog driver
 *
 * returns 0 on success, <0 on failure
 *
 * registers the file handlers and the reboot notifier
 */
static int __init wdrtas_init(void)
{
        if (wdrtas_get_tokens())
                return -ENODEV;

        if (wdrtas_register_devs())
                return -ENODEV;

        if (register_reboot_notifier(&wdrtas_notifier)) {
                pr_err("could not register reboot notifier. Terminating watchdog code.\n");
                wdrtas_unregister_devs();
                return -ENODEV;
        }

        if (wdrtas_token_get_sp == RTAS_UNKNOWN_SERVICE)
                wdrtas_interval = WDRTAS_DEFAULT_INTERVAL;
        else
                wdrtas_interval = wdrtas_get_interval(WDRTAS_DEFAULT_INTERVAL);

        return 0;
}

/**
 * wdrtas_exit - exit function of the watchdog driver
 *
 * unregisters the file handlers and the reboot notifier
 */
static void __exit wdrtas_exit(void)
{
        if (!wdrtas_nowayout)
                wdrtas_timer_stop();

        wdrtas_unregister_devs();

        unregister_reboot_notifier(&wdrtas_notifier);
}

module_init(wdrtas_init);
module_exit(wdrtas_exit);