[PATCH v3 1/3] dt-bindings: thermal-zones: Document critical-action

[PATCH v3 1/3] dt-bindings: thermal-zones: Document critical-action

[Fabio Estevam]

From: Fabio Estevam <festevam@denx.de>

Document the critical-action property to describe the thermal action
the OS should perform after the critical temperature is reached.

The possible values are "shutdown" and "reboot".

Signed-off-by: Fabio Estevam <festevam@denx.de>
---
Changes since v2:
- Improve the description. (Krzysztof)
- Don't repeat constraints in free form text. (Krzysztof)
- Remove the enum comments. (Krzysztof)

 .../devicetree/bindings/thermal/thermal-zones.yaml       | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
index 4f3acdc4dec0..c2e4d28f885b 100644
--- a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
+++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
@@ -75,6 +75,15 @@ patternProperties:
           framework and assumes that the thermal sensors in this zone
           support interrupts.
 
+      critical-action:
+        $ref: /schemas/types.yaml#/definitions/string
+        description:
+          The action the OS should perform after the critical temperature is reached.
+
+        enum:
+          - shutdown
+          - reboot
+
       thermal-sensors:
         $ref: /schemas/types.yaml#/definitions/phandle-array
         maxItems: 1
-- 
2.34.1

[PATCH v3 2/3] reboot: Introduce hw_protection_reboot()

[Fabio Estevam]

From: Fabio Estevam <festevam@denx.de>

Introduce hw_protection_reboot() to trigger an emergency reboot.

It is a counterpart of hw_protection_shutdown() with the difference
that it will force a reboot instead of shutdown.

The motivation for doing this is to allow the thermal subystem
to trigger a reboot when the temperature reaches the critical
temperature.

Signed-off-by: Fabio Estevam <festevam@denx.de>
---
Changes since v2:
- None

 include/linux/reboot.h |  1 +
 kernel/reboot.c        | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index 2b6bb593be5b..4a319bc24f6a 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -174,6 +174,7 @@ void ctrl_alt_del(void);
 
 extern void orderly_poweroff(bool force);
 extern void orderly_reboot(void);
+void hw_protection_reboot(const char *reason, int ms_until_forced);
 void hw_protection_shutdown(const char *reason, int ms_until_forced);
 
 /*
diff --git a/kernel/reboot.c b/kernel/reboot.c
index 3bba88c7ffc6..05333ae8bc6b 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -952,6 +952,40 @@ static void hw_failure_emergency_poweroff(int poweroff_delay_ms)
 			      msecs_to_jiffies(poweroff_delay_ms));
 }
 
+/**
+ * hw_protection_reboot - Trigger an emergency system reboot
+ *
+ * @reason:		Reason of emergency reboot to be printed.
+ * @ms_until_forced:	Time to wait for orderly reboot before tiggering a
+ *			forced reboot. Negative value disables the forced
+ *			reboot.
+ *
+ * Initiate an emergency system reboot in order to protect hardware from
+ * further damage. Usage examples include a thermal protection.
+ *
+ * NOTE: The request is ignored if protection reboot is already pending even
+ * if the previous request has given a large timeout for forced reboot.
+ * Can be called from any context.
+ */
+void hw_protection_reboot(const char *reason, int ms_until_forced)
+{
+	static atomic_t allow_proceed = ATOMIC_INIT(1);
+
+	pr_emerg("HARDWARE PROTECTION reboot (%s)\n", reason);
+
+	/* Reboot should be initiated only once. */
+	if (!atomic_dec_and_test(&allow_proceed))
+		return;
+
+	/*
+	 * Queue a backup emergency reboot in the event of
+	 * orderly_reboot failure
+	 */
+	hw_failure_emergency_poweroff(ms_until_forced);
+	orderly_reboot();
+}
+EXPORT_SYMBOL_GPL(hw_protection_reboot);
+
 /**
  * hw_protection_shutdown - Trigger an emergency system poweroff
  *
-- 
2.34.1

[PATCH v3 3/3] thermal: thermal_core: Allow rebooting after critical temp

[Fabio Estevam]

From: Fabio Estevam <festevam@denx.de>

Currently, the default mechanism is to trigger a shutdown after the
critical temperature is reached.

In some embedded cases, such behavior does not suit well, as the board may
be unattended in the field and rebooting may be a better approach.

The bootloader may also check the temperature and only allow the boot to
proceed when the temperature is below a certain threshold.

Introduce support for allowing a reboot to be triggered after the
critical temperature is reached.

If the "critical-action" devicetree property is not found, fall back to
the shutdown action to preserve the existing default behavior.

Tested on a i.MX8MM board with the following devicetree changes:

	thermal-zones {
		cpu-thermal {
			critical-action = "reboot";
		};
	};

Signed-off-by: Fabio Estevam <festevam@denx.de>
---
Changes since v2:
- None.

 drivers/thermal/thermal_core.c |  8 +++++++-
 drivers/thermal/thermal_of.c   | 27 +++++++++++++++++++++++++++
 include/linux/thermal.h        |  6 ++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index a59700593d32..f69e1667acb1 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -320,11 +320,17 @@ void thermal_zone_device_critical(struct thermal_zone_device *tz)
 	 * Its a must for forced_emergency_poweroff_work to be scheduled.
 	 */
 	int poweroff_delay_ms = CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS;
+	void (*hw_protection_action)(const char *reason, int ms_until_forced);
 
 	dev_emerg(&tz->device, "%s: critical temperature reached, "
 		  "shutting down\n", tz->type);
 
-	hw_protection_shutdown("Temperature too high", poweroff_delay_ms);
+	hw_protection_action = hw_protection_shutdown;
+
+	if (tz->action == THERMAL_CRITICAL_ACTION_REBOOT)
+		hw_protection_action = hw_protection_reboot;
+
+	hw_protection_action("Temperature too high", poweroff_delay_ms);
 }
 EXPORT_SYMBOL(thermal_zone_device_critical);
 
diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
index 4ca905723429..8bc28cba7406 100644
--- a/drivers/thermal/thermal_of.c
+++ b/drivers/thermal/thermal_of.c
@@ -218,6 +218,31 @@ static struct device_node *of_thermal_zone_find(struct device_node *sensor, int
 	return tz;
 }
 
+static const char * const critical_actions[] = {
+	[THERMAL_CRITICAL_ACTION_SHUTDOWN]	= "shutdown",
+	[THERMAL_CRITICAL_ACTION_REBOOT]	= "reboot",
+};
+
+static void thermal_of_get_critical_action(struct device_node *np,
+					   enum thermal_action *action)
+{
+	const char *action_string;
+	int i, ret;
+
+	ret = of_property_read_string(np, "critical-action", &action_string);
+	if (ret < 0)
+		goto out_default_action;
+
+	for (i = 0; i < ARRAY_SIZE(critical_actions); i++)
+		if (!strcasecmp(action_string, critical_actions[i])) {
+			*action = i;
+			return;
+		}
+
+out_default_action:
+	*action = THERMAL_CRITICAL_ACTION_SHUTDOWN;
+}
+
 static int thermal_of_monitor_init(struct device_node *np, int *delay, int *pdelay)
 {
 	int ret;
@@ -516,6 +541,8 @@ static struct thermal_zone_device *thermal_of_zone_register(struct device_node *
 		goto out_kfree_trips;
 	}
 
+	thermal_of_get_critical_action(np, &tz->action);
+
 	ret = thermal_zone_device_enable(tz);
 	if (ret) {
 		pr_err("Failed to enabled thermal zone '%s', id=%d: %d\n",
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index b449a46766f5..08854f640db9 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -34,6 +34,11 @@ struct thermal_cooling_device;
 struct thermal_instance;
 struct thermal_attr;
 
+enum thermal_action {
+	THERMAL_CRITICAL_ACTION_SHUTDOWN, /* shutdown when crit temperature is reached */
+	THERMAL_CRITICAL_ACTION_REBOOT, /* reboot when crit temperature is reached */
+};
+
 enum thermal_trend {
 	THERMAL_TREND_STABLE, /* temperature is stable */
 	THERMAL_TREND_RAISING, /* temperature is raising */
@@ -187,6 +192,7 @@ struct thermal_zone_device {
 	struct list_head node;
 	struct delayed_work poll_queue;
 	enum thermal_notify_event notify_event;
+	enum thermal_action action;
 };
 
 /**
-- 
2.34.1

Re: [PATCH v3 1/3] dt-bindings: thermal-zones: Document critical-action

[Krzysztof Kozlowski]

On 28/08/2023 21:59, Fabio Estevam wrote:
> From: Fabio Estevam <festevam@denx.de>
> 
> Document the critical-action property to describe the thermal action
> the OS should perform after the critical temperature is reached.


We see that from the diff. You should explain here why you need it, why
this is good idea. You should provide here answers to my concerns on v1,
so you do not get exactly the same question from Conor or Rob or anyone
else.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof