// 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 whith LPAR.
   *
   * On LPAR, the watchdog will always trigger a system restart. the module
   * paramter cmd is meaningless here.
   *

   *
   * Copyright IBM Corp. 2004, 2013
   * Author(s): Arnd Bergmann (arndb@de.ibm.com)
   *	      Philipp Hachtmann (phacht@de.ibm.com)
   *
   */
  
  #define KMSG_COMPONENT "diag288_wdt"
  #define pr_fmt(fmt) KMSG_COMPONENT ": " 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 <linux/suspend.h>
  #include <asm/ebcdic.h>

  #include <asm/diag.h>

  #include <linux/io.h>

  
  #define MAX_CMDLEN 240
  #define DEFAULT_CMD "SYSTEM RESTART"
  
  #define MIN_INTERVAL 15     /* Minimal time supported by diag88 */
  #define MAX_INTERVAL 3600   /* One hour should be enough - pure estimation */
  
  #define WDT_DEFAULT_TIMEOUT 30
  
  /* Function codes - init, change, cancel */
  #define WDT_FUNC_INIT 0
  #define WDT_FUNC_CHANGE 1
  #define WDT_FUNC_CANCEL 2
  #define WDT_FUNC_CONCEAL 0x80000000

  /* Action codes for LPAR watchdog */
  #define LPARWDT_RESTART 0

  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 int __diag288(unsigned int func, unsigned int timeout,
  		     unsigned long action, unsigned int len)
  {
  	register unsigned long __func asm("2") = func;
  	register unsigned long __timeout asm("3") = timeout;
  	register unsigned long __action asm("4") = action;
  	register unsigned long __len asm("5") = len;
  	int err;
  
  	err = -EINVAL;
  	asm volatile(
  		"	diag	%1, %3, 0x288
  "
  		"0:	la	%0, 0
  "
  		"1:
  "
  		EX_TABLE(0b, 1b)
  		: "+d" (err) : "d"(__func), "d"(__timeout),
  		  "d"(__action), "d"(__len) : "1", "cc");
  	return err;
  }
  
  static int __diag288_vm(unsigned int  func, unsigned int timeout,
  			char *cmd, size_t len)
  {

  	diag_stat_inc(DIAG_STAT_X288);

  	return __diag288(func, timeout, virt_to_phys(cmd), len);
  }

  static int __diag288_lpar(unsigned int func, unsigned int timeout,
  			  unsigned long action)
  {

  	diag_stat_inc(DIAG_STAT_X288);

  	return __diag288(func, timeout, action, 0);
  }

  static unsigned long wdt_status;
  
  #define DIAG_WDOG_BUSY	0

  static int wdt_start(struct watchdog_device *dev)
  {
  	char *ebc_cmd;
  	size_t len;
  	int ret;
  	unsigned int func;

  	if (test_and_set_bit(DIAG_WDOG_BUSY, &wdt_status))
  		return -EBUSY;

  	ret = -ENODEV;
  
  	if (MACHINE_IS_VM) {
  		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);

  		if (!ebc_cmd) {
  			clear_bit(DIAG_WDOG_BUSY, &wdt_status);

  			return -ENOMEM;

  		}

  		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
  		ASCEBC(ebc_cmd, MAX_CMDLEN);
  		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
  
  		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
  			: WDT_FUNC_INIT;
  		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
  		WARN_ON(ret != 0);
  		kfree(ebc_cmd);

  	} else {

  		ret = __diag288_lpar(WDT_FUNC_INIT,
  				     dev->timeout, LPARWDT_RESTART);
  	}

  	if (ret) {
  		pr_err("The watchdog cannot be activated
  ");

  		clear_bit(DIAG_WDOG_BUSY, &wdt_status);

  		return ret;
  	}

  	return 0;
  }
  
  static int wdt_stop(struct watchdog_device *dev)
  {
  	int ret;

  	diag_stat_inc(DIAG_STAT_X288);

  	ret = __diag288(WDT_FUNC_CANCEL, 0, 0, 0);

  
  	clear_bit(DIAG_WDOG_BUSY, &wdt_status);

  	return ret;
  }
  
  static int wdt_ping(struct watchdog_device *dev)
  {
  	char *ebc_cmd;
  	size_t len;
  	int ret;
  	unsigned int func;
  
  	ret = -ENODEV;
  
  	if (MACHINE_IS_VM) {
  		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
  		if (!ebc_cmd)
  			return -ENOMEM;
  		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
  		ASCEBC(ebc_cmd, MAX_CMDLEN);
  		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
  
  		/*
  		 * 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_vm(func, dev->timeout, ebc_cmd, len);
  		WARN_ON(ret != 0);
  		kfree(ebc_cmd);

  	} else {

  		ret = __diag288_lpar(WDT_FUNC_CHANGE, dev->timeout, 0);

  	}

  	if (ret)
  		pr_err("The watchdog timer cannot be started or reset
  ");
  	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,
  };
  
  /*
   * It makes no sense to go into suspend while the watchdog is running.
   * Depending on the memory size, the watchdog might trigger, while we
   * are still saving the memory.

   */
  static int wdt_suspend(void)
  {

  	if (test_and_set_bit(DIAG_WDOG_BUSY, &wdt_status)) {

  		pr_err("Linux cannot be suspended while the watchdog is in use
  ");
  		return notifier_from_errno(-EBUSY);
  	}
  	return NOTIFY_DONE;
  }
  
  static int wdt_resume(void)
  {

  	clear_bit(DIAG_WDOG_BUSY, &wdt_status);

  	return NOTIFY_DONE;
  }
  
  static int wdt_power_event(struct notifier_block *this, unsigned long event,
  			   void *ptr)
  {
  	switch (event) {
  	case PM_POST_HIBERNATION:
  	case PM_POST_SUSPEND:
  		return wdt_resume();
  	case PM_HIBERNATION_PREPARE:
  	case PM_SUSPEND_PREPARE:
  		return wdt_suspend();
  	default:
  		return NOTIFY_DONE;
  	}
  }
  
  static struct notifier_block wdt_power_notifier = {
  	.notifier_call = wdt_power_event,
  };
  
  static int __init diag288_init(void)
  {
  	int ret;
  	char ebc_begin[] = {
  		194, 197, 199, 201, 213
  	};
  
  	watchdog_set_nowayout(&wdt_dev, nowayout_info);
  
  	if (MACHINE_IS_VM) {

  		if (__diag288_vm(WDT_FUNC_INIT, 15,
  				 ebc_begin, sizeof(ebc_begin)) != 0) {
  			pr_err("The watchdog cannot be initialized
  ");
  			return -EINVAL;
  		}

  	} else {

  		if (__diag288_lpar(WDT_FUNC_INIT, 30, LPARWDT_RESTART)) {
  			pr_err("The watchdog cannot be initialized
  ");
  			return -EINVAL;
  		}

  	}

  	if (__diag288_lpar(WDT_FUNC_CANCEL, 0, 0)) {

  		pr_err("The watchdog cannot be deactivated
  ");
  		return -EINVAL;
  	}
  
  	ret = register_pm_notifier(&wdt_power_notifier);
  	if (ret)
  		return ret;
  
  	ret = watchdog_register_device(&wdt_dev);
  	if (ret)
  		unregister_pm_notifier(&wdt_power_notifier);
  
  	return ret;
  }
  
  static void __exit diag288_exit(void)
  {
  	watchdog_unregister_device(&wdt_dev);
  	unregister_pm_notifier(&wdt_power_notifier);
  }
  
  module_init(diag288_init);
  module_exit(diag288_exit);