Merge tag 'tags/restart-handler-for-v3.18' into next

Immutable branch with restart handler patches for v3.18

arch/arm/kernel/process.c

@@ -114,18 +114,13 @@ void soft_restart(unsigned long addr)
 	BUG();
 }
 
-static void null_restart(enum reboot_mode reboot_mode, const char *cmd)
-{
-}
-
 /*
  * Function pointers to optional machine specific functions
  */
 void (*pm_power_off)(void);
 EXPORT_SYMBOL(pm_power_off);
 
-void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd) = null_restart;
-EXPORT_SYMBOL_GPL(arm_pm_restart);
+void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
 
 /*
  * This is our default idle handler.
@@ -230,7 +225,10 @@ void machine_restart(char *cmd)
 	local_irq_disable();
 	smp_send_stop();
 
-	arm_pm_restart(reboot_mode, cmd);
+	if (arm_pm_restart)
+		arm_pm_restart(reboot_mode, cmd);
+	else
+		do_kernel_restart(cmd);
 
 	/* Give a grace period for failure to restart of 1s */
 	mdelay(1000);

arch/arm64/kernel/process.c

@@ -98,7 +98,6 @@ void (*pm_power_off)(void);
 EXPORT_SYMBOL_GPL(pm_power_off);
 
 void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
-EXPORT_SYMBOL_GPL(arm_pm_restart);
 
 /*
  * This is our default idle handler.
@@ -180,6 +179,8 @@ void machine_restart(char *cmd)
 	/* Now call the architecture specific reboot code. */
 	if (arm_pm_restart)
 		arm_pm_restart(reboot_mode, cmd);
+	else
+		do_kernel_restart(cmd);
 
 	/*
 	 * Whoops - the architecture was unable to reboot.

drivers/power/reset/restart-poweroff.c

@@ -20,7 +20,8 @@
 
 static void restart_poweroff_do_poweroff(void)
 {
-	arm_pm_restart(REBOOT_HARD, NULL);
+	reboot_mode = REBOOT_HARD;
+	machine_restart(NULL);
 }
 
 static int restart_poweroff_probe(struct platform_device *pdev)

drivers/watchdog/alim7101_wdt.c

@@ -301,6 +301,28 @@ static struct miscdevice wdt_miscdev = {
 	.fops	=	&wdt_fops,
 };
 
+static int wdt_restart_handle(struct notifier_block *this, unsigned long mode,
+			      void *cmd)
+{
+	/*
+	 * Cobalt devices have no way of rebooting themselves other
+	 * than getting the watchdog to pull reset, so we restart the
+	 * watchdog on reboot with no heartbeat.
+	 */
+	wdt_change(WDT_ENABLE);
+
+	/* loop until the watchdog fires */
+	while (true)
+		;
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block wdt_restart_handler = {
+	.notifier_call = wdt_restart_handle,
+	.priority = 128,
+};
+
 /*
  *	Notifier for system down
  */
@@ -311,15 +333,6 @@ static int wdt_notify_sys(struct notifier_block *this,
 	if (code == SYS_DOWN || code == SYS_HALT)
 		wdt_turnoff();
 
-	if (code == SYS_RESTART) {
-		/*
-		 * Cobalt devices have no way of rebooting themselves other
-		 * than getting the watchdog to pull reset, so we restart the
-		 * watchdog on reboot with no heartbeat
-		 */
-		wdt_change(WDT_ENABLE);
-		pr_info("Watchdog timer is now enabled with no heartbeat - should reboot in ~1 second\n");
-	}
 	return NOTIFY_DONE;
 }
 
@@ -338,6 +351,7 @@ static void __exit alim7101_wdt_unload(void)
 	/* Deregister */
 	misc_deregister(&wdt_miscdev);
 	unregister_reboot_notifier(&wdt_notifier);
+	unregister_restart_handler(&wdt_restart_handler);
 	pci_dev_put(alim7101_pmu);
 }
 
@@ -390,11 +404,17 @@ static int __init alim7101_wdt_init(void)
 		goto err_out;
 	}
 
+	rc = register_restart_handler(&wdt_restart_handler);
+	if (rc) {
+		pr_err("cannot register restart handler (err=%d)\n", rc);
+		goto err_out_reboot;
+	}
+
 	rc = misc_register(&wdt_miscdev);
 	if (rc) {
 		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
 		       wdt_miscdev.minor, rc);
-		goto err_out_reboot;
+		goto err_out_restart;
 	}
 
 	if (nowayout)
@@ -404,6 +424,8 @@ static int __init alim7101_wdt_init(void)
 		timeout, nowayout);
 	return 0;
 
+err_out_restart:
+	unregister_restart_handler(&wdt_restart_handler);
 err_out_reboot:
 	unregister_reboot_notifier(&wdt_notifier);
 err_out:

drivers/watchdog/moxart_wdt.c

@@ -15,12 +15,12 @@
 #include <linux/module.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
+#include <linux/notifier.h>
 #include <linux/platform_device.h>
+#include <linux/reboot.h>
 #include <linux/watchdog.h>
 #include <linux/moduleparam.h>
 
-#include <asm/system_misc.h>
-
 #define REG_COUNT			0x4
 #define REG_MODE			0x8
 #define REG_ENABLE			0xC
@@ -29,17 +29,22 @@ struct moxart_wdt_dev {
 	struct watchdog_device dev;
 	void __iomem *base;
 	unsigned int clock_frequency;
+	struct notifier_block restart_handler;
 };
 
-static struct moxart_wdt_dev *moxart_restart_ctx;
-
 static int heartbeat;
 
-static void moxart_wdt_restart(enum reboot_mode reboot_mode, const char *cmd)
+static int moxart_restart_handle(struct notifier_block *this,
+				 unsigned long mode, void *cmd)
 {
-	writel(1, moxart_restart_ctx->base + REG_COUNT);
-	writel(0x5ab9, moxart_restart_ctx->base + REG_MODE);
-	writel(0x03, moxart_restart_ctx->base + REG_ENABLE);
+	struct moxart_wdt_dev *moxart_wdt = container_of(this,
+							 struct moxart_wdt_dev,
+							 restart_handler);
+	writel(1, moxart_wdt->base + REG_COUNT);
+	writel(0x5ab9, moxart_wdt->base + REG_MODE);
+	writel(0x03, moxart_wdt->base + REG_ENABLE);
+
+	return NOTIFY_DONE;
 }
 
 static int moxart_wdt_stop(struct watchdog_device *wdt_dev)
@@ -136,8 +141,12 @@ static int moxart_wdt_probe(struct platform_device *pdev)
 	if (err)
 		return err;
 
-	moxart_restart_ctx = moxart_wdt;
-	arm_pm_restart = moxart_wdt_restart;
+	moxart_wdt->restart_handler.notifier_call = moxart_restart_handle;
+	moxart_wdt->restart_handler.priority = 128;
+	err = register_restart_handler(&moxart_wdt->restart_handler);
+	if (err)
+		dev_err(dev, "cannot register restart notifier (err=%d)\n",
+			err);
 
 	dev_dbg(dev, "Watchdog enabled (heartbeat=%d sec, nowayout=%d)\n",
 		moxart_wdt->dev.timeout, nowayout);
@@ -149,9 +158,8 @@ static int moxart_wdt_remove(struct platform_device *pdev)
 {
 	struct moxart_wdt_dev *moxart_wdt = platform_get_drvdata(pdev);
 
-	arm_pm_restart = NULL;
+	unregister_restart_handler(&moxart_wdt->restart_handler);
 	moxart_wdt_stop(&moxart_wdt->dev);
-	watchdog_unregister_device(&moxart_wdt->dev);
 
 	return 0;
 }

drivers/watchdog/sunxi_wdt.c

@@ -21,14 +21,13 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
+#include <linux/notifier.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/reboot.h>
 #include <linux/types.h>
 #include <linux/watchdog.h>
 
-#include <asm/system_misc.h>
-
 #define WDT_MAX_TIMEOUT         16
 #define WDT_MIN_TIMEOUT         1
 #define WDT_MODE_TIMEOUT(n)     ((n) << 3)
@@ -50,6 +49,7 @@ static unsigned int timeout = WDT_MAX_TIMEOUT;
 struct sunxi_wdt_dev {
 	struct watchdog_device wdt_dev;
 	void __iomem *wdt_base;
+	struct notifier_block restart_handler;
 };
 
 /*
@@ -74,24 +74,29 @@ static const int wdt_timeout_map[] = {
 	[16] = 0xB, /* 16s */
 };
 
-static void __iomem *reboot_wdt_base;
 
-static void sun4i_wdt_restart(enum reboot_mode mode, const char *cmd)
+static int sunxi_restart_handle(struct notifier_block *this, unsigned long mode,
+				void *cmd)
 {
+	struct sunxi_wdt_dev *sunxi_wdt = container_of(this,
+						       struct sunxi_wdt_dev,
+						       restart_handler);
+	void __iomem *wdt_base = sunxi_wdt->wdt_base;
+
 	/* Enable timer and set reset bit in the watchdog */
-	writel(WDT_MODE_EN | WDT_MODE_RST_EN, reboot_wdt_base + WDT_MODE);
+	writel(WDT_MODE_EN | WDT_MODE_RST_EN, wdt_base + WDT_MODE);
 
 	/*
 	 * Restart the watchdog. The default (and lowest) interval
 	 * value for the watchdog is 0.5s.
 	 */
-	writel(WDT_CTRL_RELOAD, reboot_wdt_base + WDT_CTRL);
+	writel(WDT_CTRL_RELOAD, wdt_base + WDT_CTRL);
 
 	while (1) {
 		mdelay(5);
-		writel(WDT_MODE_EN | WDT_MODE_RST_EN,
-		       reboot_wdt_base + WDT_MODE);
+		writel(WDT_MODE_EN | WDT_MODE_RST_EN, wdt_base + WDT_MODE);
 	}
+	return NOTIFY_DONE;
 }
 
 static int sunxi_wdt_ping(struct watchdog_device *wdt_dev)
@@ -205,8 +210,12 @@ static int sunxi_wdt_probe(struct platform_device *pdev)
 	if (unlikely(err))
 		return err;
 
-	reboot_wdt_base = sunxi_wdt->wdt_base;
-	arm_pm_restart = sun4i_wdt_restart;
+	sunxi_wdt->restart_handler.notifier_call = sunxi_restart_handle;
+	sunxi_wdt->restart_handler.priority = 128;
+	err = register_restart_handler(&sunxi_wdt->restart_handler);
+	if (err)
+		dev_err(&pdev->dev,
+			"cannot register restart handler (err=%d)\n", err);
 
 	dev_info(&pdev->dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)",
 			sunxi_wdt->wdt_dev.timeout, nowayout);
@@ -218,7 +227,7 @@ static int sunxi_wdt_remove(struct platform_device *pdev)
 {
 	struct sunxi_wdt_dev *sunxi_wdt = platform_get_drvdata(pdev);
 
-	arm_pm_restart = NULL;
+	unregister_restart_handler(&sunxi_wdt->restart_handler);
 
 	watchdog_unregister_device(&sunxi_wdt->wdt_dev);
 	watchdog_set_drvdata(&sunxi_wdt->wdt_dev, NULL);

include/linux/reboot.h

@@ -38,6 +38,9 @@ extern int reboot_force;
 extern int register_reboot_notifier(struct notifier_block *);
 extern int unregister_reboot_notifier(struct notifier_block *);
 
+extern int register_restart_handler(struct notifier_block *);
+extern int unregister_restart_handler(struct notifier_block *);
+extern void do_kernel_restart(char *cmd);
 
 /*
  * Architecture-specific implementations of sys_reboot commands.

kernel/reboot.c

@@ -104,6 +104,87 @@ int unregister_reboot_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_reboot_notifier);
 
+/*
+ *	Notifier list for kernel code which wants to be called
+ *	to restart the system.
+ */
+static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
+
+/**
+ *	register_restart_handler - Register function to be called to reset
+ *				   the system
+ *	@nb: Info about handler function to be called
+ *	@nb->priority:	Handler priority. Handlers should follow the
+ *			following guidelines for setting priorities.
+ *			0:	Restart handler of last resort,
+ *				with limited restart capabilities
+ *			128:	Default restart handler; use if no other
+ *				restart handler is expected to be available,
+ *				and/or if restart functionality is
+ *				sufficient to restart the entire system
+ *			255:	Highest priority restart handler, will
+ *				preempt all other restart handlers
+ *
+ *	Registers a function with code to be called to restart the
+ *	system.
+ *
+ *	Registered functions will be called from machine_restart as last
+ *	step of the restart sequence (if the architecture specific
+ *	machine_restart function calls do_kernel_restart - see below
+ *	for details).
+ *	Registered functions are expected to restart the system immediately.
+ *	If more than one function is registered, the restart handler priority
+ *	selects which function will be called first.
+ *
+ *	Restart handlers are expected to be registered from non-architecture
+ *	code, typically from drivers. A typical use case would be a system
+ *	where restart functionality is provided through a watchdog. Multiple
+ *	restart handlers may exist; for example, one restart handler might
+ *	restart the entire system, while another only restarts the CPU.
+ *	In such cases, the restart handler which only restarts part of the
+ *	hardware is expected to register with low priority to ensure that
+ *	it only runs if no other means to restart the system is available.
+ *
+ *	Currently always returns zero, as atomic_notifier_chain_register()
+ *	always returns zero.
+ */
+int register_restart_handler(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&restart_handler_list, nb);
+}
+EXPORT_SYMBOL(register_restart_handler);
+
+/**
+ *	unregister_restart_handler - Unregister previously registered
+ *				     restart handler
+ *	@nb: Hook to be unregistered
+ *
+ *	Unregisters a previously registered restart handler function.
+ *
+ *	Returns zero on success, or %-ENOENT on failure.
+ */
+int unregister_restart_handler(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_unregister(&restart_handler_list, nb);
+}
+EXPORT_SYMBOL(unregister_restart_handler);
+
+/**
+ *	do_kernel_restart - Execute kernel restart handler call chain
+ *
+ *	Calls functions registered with register_restart_handler.
+ *
+ *	Expected to be called from machine_restart as last step of the restart
+ *	sequence.
+ *
+ *	Restarts the system immediately if a restart handler function has been
+ *	registered. Otherwise does nothing.
+ */
+void do_kernel_restart(char *cmd)
+{
+	atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
+}
+
 void migrate_to_reboot_cpu(void)
 {
 	/* The boot cpu is always logical cpu 0 */