thermal/thermal_of: Allow rebooting after critical temp

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.

If a custom ops->critical exists, then it takes preference over
critical-actions.

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

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

Signed-off-by: Fabio Estevam <[email protected]>
Signed-off-by: Daniel Lezcano <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Fabio Estevam

drivers/thermal/thermal_of.c

@@ -475,6 +475,7 @@ static struct thermal_zone_device *thermal_of_zone_register(struct device_node *
 	struct thermal_zone_params tzp = {};
 	struct thermal_zone_device_ops *of_ops;
 	struct device_node *np;
+	const char *action;
 	int delay, pdelay;
 	int ntrips, mask;
 	int ret;
@@ -511,6 +512,11 @@ static struct thermal_zone_device *thermal_of_zone_register(struct device_node *
 
 	mask = GENMASK_ULL((ntrips) - 1, 0);
 
+	ret = of_property_read_string(np, "critical-action", &action);
+	if (!ret)
+		if (!of_ops->critical && !strcasecmp(action, "reboot"))
+			of_ops->critical = thermal_zone_device_critical_reboot;
+
 	tz = thermal_zone_device_register_with_trips(np->name, trips, ntrips,
 						     mask, data, of_ops, &tzp,
 						     pdelay, delay);