On 6/26/25 11:41 PM, Niklas Söderlund wrote:
Hello Niklas,
+&a76_3 {
+ a76_3_thermal_idle: thermal-idle {
+ #cooling-cells = <2>;
+ duration-us = <10000>;
+ exit-latency-us = <500>;
+ };
+};
I did not know you could do this and use it as a cooling device, thanks
for teaching me something new!
You could, although the cooling effect may vary. Some cores enter e.g.
clock stop during idle and then they really cool down, some do not.
+/* THS sensors in SoC, critical temperature trip point is 100C */
+&sensor1_crit {
+ temperature = <100000>;
+};
+
+&sensor2_crit {
+ temperature = <100000>;
+};
+
+&sensor3_crit {
+ temperature = <100000>;
+};
+
+&sensor4_crit {
+ temperature = <100000>;
+};
+
+&sensor_thermal_cr52 {
+ critical-action = "shutdown";
+};
+
+&sensor_thermal_cnn {
+ critical-action = "shutdown";
+};
Is this not the default action for critical trip points? In my testing
in the past R-Car systems have always shutdown when the critical trip is
reached.
It isn't quite that clear cut.
drivers/thermal/thermal_of.c thermal_of_zone_register() contains this
piece of code:
"
407 ret = of_property_read_string(np, "critical-action", &action);
408 if (!ret && !of_ops.critical) {
409 if (!strcasecmp(action, "reboot"))
410 of_ops.critical =
thermal_zone_device_critical_reboot;
411 else if (!strcasecmp(action, "shutdown"))
412 of_ops.critical =
thermal_zone_device_critical_shutdown;
413 }
"
If "critical-action" DT property is not set, then of_ops.critical are
not modified.
drivers/thermal/thermal_core.c thermal_zone_device_register_with_trips()
contains this piece of code:
1571 if (!tz->ops.critical)
1572 tz->ops.critical = thermal_zone_device_critical;
If (in case of OF) of_ops.critical is not set, use
thermal_zone_device_critical() handler.
There is a slight difference:
- If critical-action = "shutdown" is set in DT, then handler
thermal_zone_device_critical_shutdown() is called, which is a wrapper
around thermal_zone_device_halt(tz, HWPROT_ACT_SHUTDOWN);
- If critical-action = "shutdown" is NOT set in DT, then handler
thermal_zone_device_critical() is called, which is a wrapper
around thermal_zone_device_halt(tz, HWPROT_ACT_DEFAULT);
thermal_zone_device_halt() itself is a wrapper around
__hw_protection_trigger(msg, poweroff_delay_ms, action); , where action
is either HWPROT_ACT_SHUTDOWN or HWPROT_ACT_DEFAULT , which is handled
in kernel/reboot.c __hw_protection_trigger() implementation :
1028 void __hw_protection_trigger(const char *reason, int ms_until_forced,
1029 enum hw_protection_action action)
1030 {
1031 static atomic_t allow_proceed = ATOMIC_INIT(1);
1032
1033 if (action == HWPROT_ACT_DEFAULT)
1034 action = hw_protection_action;
In case of HWPROT_ACT_DEFAULT , the 'hw_protection_action' which is
assigned into 'action' can be overridden, either via sysfs write, or
hw_protection_ kernel command line parameter . In case of
HWPROT_ACT_SHUTDOWN , the action cannot be overridden .
In case this hardware starts to melt, we surely want HWPROT_ACT_SHUTDOWN
with no override options ...
If it's not I think we should move these to r8a779g0.dtsi. And
likely add them for all other SoCs too?
... the other hardware has non-optional heatsink, where override-able
HWPROT_ACT_DEFAULT is the right option I think .
