Hi Marek,

On Wed, 25 Jun 2025 at 12:03, Marek Vasut
[off-list ref] wrote:

Since the Sparrow Hawk has a smaller PCB than the White Hawk, it tends
to generate more heat. To prevent potential damage to the board, adjust
the temperature trip points.

Add four "passive" trip points which increasingly throttle the CPU to
prevent overheating. The first trip point at 68°C disables the 1.8 GHz
and 1.7 GHz modes and limits the CPU to 1.5 GHz frequency. The second
trip point at 72°C disables the 1.5 GHz mode and limits the CPU to 1.0
GHz frequency. The third trip point at 76°C uses thermal-idle to start
inserting idle cycles into the CPU instruction stream to cool the CPU
cores down. The fourth and last trip point at 80°C disables the 1.0 GHz
mode and limits the CPU to 500 MHz frequency.

In case the SoC heats up further, in case either of the thermal sensors
readings passes the 100°C, a thermal shutdown is triggered to prevent
any damage to the hardware.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

Thanks for your patch!

Please keep nodes sorted (alphabetically by label).

+       #cooling-cells = <2>;

This is only present for the first CPU core, and map{0,1,3} refer
only to a76_0, because all four CPU cores are driven by a single clock
(Z0), right?

+
+       a76_0_thermal_idle: thermal-idle {
+               #cooling-cells = <2>;
+               duration-us = <10000>;
+               exit-latency-us = <500>;
+       };
+};

+/* THS sensor in SoC near CA76 cores does more progressive cooling. */
+&sensor_thermal_ca76 {
+       critical-action = "shutdown";
+
+       cooling-maps {
+               /*
+                * The cooling-device minimum and maximum parameters inversely
+                * match opp-table-0 {} node entries in r8a779g0.dtsi, in other
+                * words, 0 refers to 1.8 GHz OPP and 4 refers to 500 MHz OPP.
+                * This is because they refer to cooling levels, where maximum
+                * cooling level happens at 500 MHz OPP, when the CPU core is
+                * running slowly and therefore generates least heat.

That applies to cooling-device = <&a76_[0-3] ...>...

+                */
+               map0 {
+                       /* At 68C, inhibit 1.7 GHz and 1.8 GHz modes */
+                       trip = <&sensor3_passive_low>;
+                       cooling-device = <&a76_0 2 4>;
+                       contribution = <128>;
+               };
+
+               map1 {
+                       /* At 72C, inhibit 1.5 GHz mode */
+                       trip = <&sensor3_passive_mid>;
+                       cooling-device = <&a76_0 3 4>;
+                       contribution = <256>;
+               };
+
+               map2 {
+                       /* At 76C, start injecting idle states */
+                       trip = <&sensor3_passive_hi>;
+                       cooling-device = <&a76_0_thermal_idle 0 80>,
+                                        <&a76_1_thermal_idle 0 80>,
+                                        <&a76_2_thermal_idle 0 80>,
+                                        <&a76_3_thermal_idle 0 80>;

... but what do "0 80" refer to? I couldn't find in the thermal-idle
bindings what exactly are the minimum and maximum cooling states here.

+                       contribution = <512>;
+               };

The rest LGTM, so with the sort order fixed, and the thermal-idle
states clarified:
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds