[PATCH 1/6] kernel/reboot: distinguish between cold and warm

[Benjamin Bara <bbara93@gmail.com>]

From: Benjamin Bara <benjamin.bara@skidata.com>

As a couple of PMICs support warm and cold resets (e.g. tps65219 or
pca9450) and the 'reboot_mode' kernel parameter allows to specify the
reboot mode, distinguish between cold and warm reboot handlers.
This is done by maintaining two different restart handler lists. When
the mode is unspecified, the cold restart handlers are preferred
(independent of their actual priority).

Signed-off-by: Benjamin Bara <benjamin.bara@skidata.com>
---
 include/linux/reboot.h | 22 ++++++++++++
 kernel/reboot.c        | 92 ++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 108 insertions(+), 6 deletions(-)

diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index 2b6bb593be5b..05199aedb696 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -119,6 +119,20 @@ enum sys_off_mode {
 	 * Handlers restart system. Handlers are disallowed to sleep.
 	 */
 	SYS_OFF_MODE_RESTART,
+
+	/**
+	 * @SYS_OFF_MODE_RESTART_COLD:
+	 *
+	 * Handlers cold restart system. Handlers are disallowed to sleep.
+	 */
+	SYS_OFF_MODE_RESTART_COLD,
+
+	/**
+	 * @SYS_OFF_MODE_RESTART_WARM:
+	 *
+	 * Handlers warm restart system. Handlers are disallowed to sleep.
+	 */
+	SYS_OFF_MODE_RESTART_WARM,
 };
 
 /**
@@ -157,6 +171,14 @@ int devm_register_restart_handler(struct device *dev,
 				  int (*callback)(struct sys_off_data *data),
 				  void *cb_data);
 
+int devm_register_cold_restart_handler(struct device *dev,
+				       int (*callback)(struct sys_off_data *data),
+				       void *cb_data);
+
+int devm_register_warm_restart_handler(struct device *dev,
+				       int (*callback)(struct sys_off_data *data),
+				       void *cb_data);
+
 int register_platform_power_off(void (*power_off)(void));
 void unregister_platform_power_off(void (*power_off)(void));
 
diff --git a/kernel/reboot.c b/kernel/reboot.c
index 3bba88c7ffc6..d0d3faf70a79 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -146,9 +146,15 @@ EXPORT_SYMBOL(devm_register_reboot_notifier);
 
 /*
  *	Notifier list for kernel code which wants to be called
- *	to restart the system.
+ *	to cold restart the system.
  */
-static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
+static ATOMIC_NOTIFIER_HEAD(cold_restart_handler_list);
+
+/*
+ *	Notifier list for kernel code which wants to be called
+ *	to warm restart the system.
+ */
+static ATOMIC_NOTIFIER_HEAD(warm_restart_handler_list);
 
 /**
  *	register_restart_handler - Register function to be called to reset
@@ -190,7 +196,11 @@ static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
  */
 int register_restart_handler(struct notifier_block *nb)
 {
-	return atomic_notifier_chain_register(&restart_handler_list, nb);
+	/*
+	 * Store all non-devm-based handlers in the warm list to ensure that the
+	 * "specified" handler are preferred over the "unspecified" ones.
+	 */
+	return atomic_notifier_chain_register(&warm_restart_handler_list, nb);
 }
 EXPORT_SYMBOL(register_restart_handler);
 
@@ -205,7 +215,14 @@ EXPORT_SYMBOL(register_restart_handler);
  */
 int unregister_restart_handler(struct notifier_block *nb)
 {
-	return atomic_notifier_chain_unregister(&restart_handler_list, nb);
+	int ret;
+
+	ret = atomic_notifier_chain_unregister(&warm_restart_handler_list, nb);
+	if (ret == -ENOENT)
+		ret = atomic_notifier_chain_unregister(&cold_restart_handler_list,
+						       nb);
+
+	return ret;
 }
 EXPORT_SYMBOL(unregister_restart_handler);
 
@@ -222,7 +239,18 @@ EXPORT_SYMBOL(unregister_restart_handler);
  */
 void do_kernel_restart(char *cmd)
 {
-	atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
+	/*
+	 * REBOOT_GPIO can be either cold or warm -> let handler decide.
+	 * Prefer cold reboot if mode not specified.
+	 */
+	if (reboot_mode == REBOOT_UNDEFINED || reboot_mode == REBOOT_GPIO ||
+	    reboot_mode == REBOOT_HARD || reboot_mode == REBOOT_COLD)
+		atomic_notifier_call_chain(&cold_restart_handler_list,
+					   reboot_mode, cmd);
+	if (reboot_mode == REBOOT_UNDEFINED || reboot_mode == REBOOT_GPIO ||
+	    reboot_mode == REBOOT_SOFT || reboot_mode == REBOOT_WARM)
+		atomic_notifier_call_chain(&warm_restart_handler_list,
+					   reboot_mode, cmd);
 }
 
 void migrate_to_reboot_cpu(void)
@@ -414,7 +442,15 @@ register_sys_off_handler(enum sys_off_mode mode,
 		break;
 
 	case SYS_OFF_MODE_RESTART:
-		handler->list = &restart_handler_list;
+		handler->list = &warm_restart_handler_list;
+		break;
+
+	case SYS_OFF_MODE_RESTART_COLD:
+		handler->list = &cold_restart_handler_list;
+		break;
+
+	case SYS_OFF_MODE_RESTART_WARM:
+		handler->list = &warm_restart_handler_list;
 		break;
 
 	default:
@@ -560,6 +596,50 @@ int devm_register_restart_handler(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(devm_register_restart_handler);
 
+/**
+ *	devm_register_cold_restart_handler - Register cold restart handler
+ *	@dev: Device that registers callback
+ *	@callback: Callback function
+ *	@cb_data: Callback's argument
+ *
+ *	Registers resource-managed sys-off handler with a default priority
+ *	and using cold restart mode.
+ *
+ *	Returns zero on success, or error code on failure.
+ */
+int devm_register_cold_restart_handler(struct device *dev,
+				       int (*callback)(struct sys_off_data *data),
+				       void *cb_data)
+{
+	return devm_register_sys_off_handler(dev,
+					     SYS_OFF_MODE_RESTART_COLD,
+					     SYS_OFF_PRIO_DEFAULT,
+					     callback, cb_data);
+}
+EXPORT_SYMBOL_GPL(devm_register_cold_restart_handler);
+
+/**
+ *	devm_register_warm_restart_handler - Register warm restart handler
+ *	@dev: Device that registers callback
+ *	@callback: Callback function
+ *	@cb_data: Callback's argument
+ *
+ *	Registers resource-managed sys-off handler with a default priority
+ *	and using warm restart mode.
+ *
+ *	Returns zero on success, or error code on failure.
+ */
+int devm_register_warm_restart_handler(struct device *dev,
+				       int (*callback)(struct sys_off_data *data),
+				       void *cb_data)
+{
+	return devm_register_sys_off_handler(dev,
+					     SYS_OFF_MODE_RESTART_WARM,
+					     SYS_OFF_PRIO_DEFAULT,
+					     callback, cb_data);
+}
+EXPORT_SYMBOL_GPL(devm_register_warm_restart_handler);
+
 static struct sys_off_handler *platform_power_off_handler;
 
 static int platform_power_off_notify(struct sys_off_data *data)

-- 
2.34.1