[PATCH V3] ARM: dts: omap3: Add cpu trips and cooling map for omap34/36 families

[Adam Ford]

Currently, OMAP3_THERMAL is disabled by default, so the bandgap sensor
is unavailable, and enabling it will somewhat increase power consumption.
However for boards which operate near their thermal limit, OMAP3_THERMAL
can be enabled and monitored to keep the processor from either running
too fast, or shutdown when it's deemed to be operating at an unsafe
thermal limit at the expense of increased power consumption.

The OMAP3530, OMAP3630, and DM3730 all show thresholds of 90C and 105C
depending on commercial or extended temperature ratings.

This patch expands the thermal information to include the limits of
80C for alert and 90C critical based on commercial temperature rating.
It sets the coolings-cells for the 34xx and 36xx CPU's which will start
to throttle back their maximum frequency when the bangap sensor reads
above the alert temerature of 80C.

For boards who which to increase the temperatures for extended
temperature ratings, these can be changed on their respective
device trees with something like:

&cpu_alert0 {
	temperature = <90000>; /* millicelsius */
};

&cpu_crit {
	temperature = <105000>; /* millicelsius */
};

Signed-off-by: Adam Ford <aford173@xxxxxxxxx>
Tested-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> # on GTA04A5 with dm3730cbp100

---
V3:  Make commercial temperature the default instead of extended temp
     Add notes about power consumption and OMAP3_THERMAL and the
     dependency of this patch to OMAP3_THERMAL.

V2:  Rebase on Linux 5.9-rc1

diff --git a/arch/arm/boot/dts/omap3-cpu-thermal.dtsi b/arch/arm/boot/dts/omap3-cpu-thermal.dtsi
index aee46fa8c055..1ed837859374 100644
--- a/arch/arm/boot/dts/omap3-cpu-thermal.dtsi
+++ b/arch/arm/boot/dts/omap3-cpu-thermal.dtsi
@@ -17,4 +17,25 @@ cpu_thermal: cpu_thermal {
 
 			/* sensor       ID */
 	thermal-sensors = <&bandgap     0>;
+
+	cpu_trips: trips {
+		cpu_alert0: cpu_alert {
+			temperature = <80000>; /* millicelsius */
+			hysteresis = <2000>; /* millicelsius */
+			type = "passive";
+		};
+		cpu_crit: cpu_crit {
+			temperature = <90000>; /* millicelsius */
+			hysteresis = <2000>; /* millicelsius */
+			type = "critical";
+		};
+	};
+
+	cpu_cooling_maps: cooling-maps {
+		map0 {
+			trip = <&cpu_alert0>;
+			cooling-device =
+				<&cpu THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
+		};
+	};
 };
diff --git a/arch/arm/boot/dts/omap34xx.dtsi b/arch/arm/boot/dts/omap34xx.dtsi
index 9c3ee4ac8165..c0dcc75833a8 100644
--- a/arch/arm/boot/dts/omap34xx.dtsi
+++ b/arch/arm/boot/dts/omap34xx.dtsi
@@ -20,6 +20,7 @@
 			operating-points-v2 = <&cpu0_opp_table>;
 
 			clock-latency = <300000>; /* From legacy driver */
+			#cooling-cells = <2>;
 		};
 	};
 
diff --git a/arch/arm/boot/dts/omap36xx.dtsi b/arch/arm/boot/dts/omap36xx.dtsi
index 9c3beefc0fe0..fadbf308feff 100644
--- a/arch/arm/boot/dts/omap36xx.dtsi
+++ b/arch/arm/boot/dts/omap36xx.dtsi
@@ -25,6 +25,7 @@
 
 			vbb-supply = <&abb_mpu_iva>;
 			clock-latency = <300000>; /* From omap-cpufreq driver */
+			#cooling-cells = <2>;
 		};
 	};
 
-- 
2.17.1