s390/watchdog: add support for LPAR operation (diag288)

Add the LPAR variant of the diag 288 watchdog to the driver.
The only available action on timeout for LPAR is a PSW restart.

Signed-off-by: Philipp Hachtmann <phacht@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/watchdog/Kconfig

@@ -1304,6 +1304,8 @@ config DIAG288_WATCHDOG
 	  provide a virtual watchdog timer to their guest that cause a
 	  user define Control Program command to be executed after a
 	  timeout.
+	  LPAR provides a very similar interface. This driver handles
+	  both.
 
 	  To compile this driver as a module, choose M here. The module
 	  will be called vmwatchdog.

drivers/watchdog/diag288_wdt.c

@@ -1,10 +1,15 @@
 /*
- * Watchdog driver for z/VM using the diag 288 interface.
+ * 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".
+ * 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)
@@ -41,6 +46,9 @@
 #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;
@@ -89,6 +97,12 @@ static int __diag288_vm(unsigned int  func, unsigned int timeout,
 	return __diag288(func, timeout, virt_to_phys(cmd), len);
 }
 
+static int __diag288_lpar(unsigned int func, unsigned int timeout,
+			  unsigned long action)
+{
+	return __diag288(func, timeout, action, 0);
+}
+
 static int wdt_start(struct watchdog_device *dev)
 {
 	char *ebc_cmd;
@@ -113,6 +127,11 @@ static int wdt_start(struct watchdog_device *dev)
 		kfree(ebc_cmd);
 	}
 
+	if (MACHINE_IS_LPAR) {
+		ret = __diag288_lpar(WDT_FUNC_INIT,
+				     dev->timeout, LPARWDT_RESTART);
+	}
+
 	if (ret) {
 		pr_err("The watchdog cannot be activated\n");
 		return ret;
@@ -149,7 +168,8 @@ static int wdt_ping(struct watchdog_device *dev)
 
 		/*
 		 * It seems to be ok to z/VM to use the init function to
-		 * retrigger the watchdog.
+		 * 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;
@@ -159,6 +179,9 @@ static int wdt_ping(struct watchdog_device *dev)
 		kfree(ebc_cmd);
 	}
 
+	if (MACHINE_IS_LPAR)
+		ret = __diag288_lpar(WDT_FUNC_CHANGE, dev->timeout, 0);
+
 	if (ret)
 		pr_err("The watchdog timer cannot be started or reset\n");
 	return ret;
@@ -256,12 +279,18 @@ static int __init diag288_init(void)
 			pr_err("The watchdog cannot be initialized\n");
 			return -EINVAL;
 		}
+	} else if (MACHINE_IS_LPAR) {
+		pr_info("The watchdog device driver detected an LPAR environment\n");
+		if (__diag288_lpar(WDT_FUNC_INIT, 30, LPARWDT_RESTART)) {
+			pr_err("The watchdog cannot be initialized\n");
+			return -EINVAL;
+		}
 	} else {
 		pr_err("Linux runs in an environment that does not support the diag288 watchdog\n");
 		return -ENODEV;
 	}
 
-	if (__diag288_vm(WDT_FUNC_CANCEL, 0, NULL, 0)) {
+	if (__diag288_lpar(WDT_FUNC_CANCEL, 0, 0)) {
 		pr_err("The watchdog cannot be deactivated\n");
 		return -EINVAL;
 	}