// SPDX-License-Identifier: GPL-2.0-only
/*
 * Watchdog driver for z/VM and LPAR using the diag 288 interface.
 *
 * Under z/VM, expiration of the watchdog will send a "system restart" command
 * to CP.
 *
 * The command can be altered using the module parameter "cmd". This is
 * not recommended because it's only supported on z/VM but not with LPAR.
 *
 * On LPAR, the watchdog will always trigger a system restart. The module
 * parameter cmd is meaningless here.
 *
 *
 * Copyright IBM Corp. 2004, 2013
 * Author(s): Arnd Bergmann (arndb@de.ibm.com)
 *            Philipp Hachtmann (phacht@de.ibm.com)
 *
 */

#define pr_fmt(fmt) "diag288_wdt: " fmt

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/watchdog.h>
#include <asm/machine.h>
#include <asm/ebcdic.h>
#include <asm/diag288.h>
#include <asm/diag.h>
#include <linux/io.h>

#define MAX_CMDLEN 240
#define DEFAULT_CMD "SYSTEM RESTART"

static char wdt_cmd[MAX_CMDLEN] = DEFAULT_CMD;
static bool conceal_on;
static bool nowayout_info = WATCHDOG_NOWAYOUT;

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Arnd Bergmann <arndb@de.ibm.com>");
MODULE_AUTHOR("Philipp Hachtmann <phacht@de.ibm.com>");

MODULE_DESCRIPTION("System z diag288  Watchdog Timer");

module_param_string(cmd, wdt_cmd, MAX_CMDLEN, 0644);
MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers (z/VM only)");

module_param_named(conceal, conceal_on, bool, 0644);
MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog is active (z/VM only)");

module_param_named(nowayout, nowayout_info, bool, 0444);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default = CONFIG_WATCHDOG_NOWAYOUT)");

MODULE_ALIAS("vmwatchdog");

static char *cmd_buf;

static int diag288(unsigned int func, unsigned int timeout,
                   unsigned long action, unsigned int len)
{
        diag_stat_inc(DIAG_STAT_X288);
        return __diag288(func, timeout, action, len);
}

static int diag288_str(unsigned int func, unsigned int timeout, char *cmd)
{
        ssize_t len;

        len = strscpy(cmd_buf, cmd, MAX_CMDLEN);
        if (len < 0)
                return len;
        ASCEBC(cmd_buf, MAX_CMDLEN);
        EBC_TOUPPER(cmd_buf, MAX_CMDLEN);

        return diag288(func, timeout, virt_to_phys(cmd_buf), len);
}

static int wdt_start(struct watchdog_device *dev)
{
        int ret;
        unsigned int func;

        if (machine_is_vm()) {
                func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
                        : WDT_FUNC_INIT;
                ret = diag288_str(func, dev->timeout, wdt_cmd);
                WARN_ON(ret != 0);
        } else {
                ret = diag288(WDT_FUNC_INIT, dev->timeout, LPARWDT_RESTART, 0);
        }

        if (ret) {
                pr_err("The watchdog cannot be activated\n");
                return ret;
        }
        return 0;
}

static int wdt_stop(struct watchdog_device *dev)
{
        return diag288(WDT_FUNC_CANCEL, 0, 0, 0);
}

static int wdt_ping(struct watchdog_device *dev)
{
        int ret;
        unsigned int func;

        if (machine_is_vm()) {
                /*
                 * It seems to be ok to z/VM to use the init function to
                 * retrigger the watchdog. On LPAR WDT_FUNC_CHANGE must
                 * be used when the watchdog is running.
                 */
                func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
                        : WDT_FUNC_INIT;

                ret = diag288_str(func, dev->timeout, wdt_cmd);
                WARN_ON(ret != 0);
        } else {
                ret = diag288(WDT_FUNC_CHANGE, dev->timeout, 0, 0);
        }

        if (ret)
                pr_err("The watchdog timer cannot be started or reset\n");
        return ret;
}

static int wdt_set_timeout(struct watchdog_device * dev, unsigned int new_to)
{
        dev->timeout = new_to;
        return wdt_ping(dev);
}

static const struct watchdog_ops wdt_ops = {
        .owner = THIS_MODULE,
        .start = wdt_start,
        .stop = wdt_stop,
        .ping = wdt_ping,
        .set_timeout = wdt_set_timeout,
};

static const struct watchdog_info wdt_info = {
        .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
        .firmware_version = 0,
        .identity = "z Watchdog",
};

static struct watchdog_device wdt_dev = {
        .parent = NULL,
        .info = &wdt_info,
        .ops = &wdt_ops,
        .bootstatus = 0,
        .timeout = WDT_DEFAULT_TIMEOUT,
        .min_timeout = MIN_INTERVAL,
        .max_timeout = MAX_INTERVAL,
};

static int __init diag288_init(void)
{
        watchdog_set_nowayout(&wdt_dev, nowayout_info);

        if (machine_is_vm()) {
                cmd_buf = kmalloc(MAX_CMDLEN, GFP_KERNEL);
                if (!cmd_buf) {
                        pr_err("The watchdog cannot be initialized\n");
                        return -ENOMEM;
                }
        }

        return watchdog_register_device(&wdt_dev);
}

static void __exit diag288_exit(void)
{
        watchdog_unregister_device(&wdt_dev);
        kfree(cmd_buf);
}

module_cpu_feature_match(S390_CPU_FEATURE_D288, diag288_init);
module_exit(diag288_exit);