ARM: tegra: acer-a500: Improve thermal zones

Use skin temperature for maintaining temperature that is suitable
specifically for A500. Add CPU thermal zone that protects silicon.
All these changes don't make a significant difference, but it is a
more correct definition of thermal zones.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra20-acer-a500-picasso.dts

@@ -1029,11 +1029,48 @@
 	};
 
 	thermal-zones {
+		/*
+		 * NCT1008 has two sensors:
+		 *
+		 *	0: internal that monitors ambient/skin temperature
+		 *	1: external that is connected to the CPU's diode
+		 *
+		 * Ideally we should use userspace thermal governor,
+		 * but it's a much more complex solution.  The "skin"
+		 * zone is a simpler solution which prevents A500 from
+		 * getting too hot from a user's tactile perspective.
+		 * The CPU zone is intended to protect silicon from damage.
+		 */
+
 		skin-thermal {
 			polling-delay-passive = <1000>; /* milliseconds */
-			polling-delay = <0>; /* milliseconds */
+			polling-delay = <5000>; /* milliseconds */
 
 			thermal-sensors = <&nct1008 0>;
+
+			trips {
+				trip0: skin-alert {
+					/* start throttling at 60C */
+					temperature = <60000>;
+					hysteresis = <200>;
+					type = "passive";
+				};
+
+				trip1: skin-crit {
+					/* shut down at 70C */
+					temperature = <70000>;
+					hysteresis = <2000>;
+					type = "critical";
+				};
+			};
+
+			cooling-maps {
+				map0 {
+					trip = <&trip0>;
+					cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
+							 <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
+				};
+			};
 		};
 
 		cpu-thermal {
@@ -1043,24 +1080,24 @@
 			thermal-sensors = <&nct1008 1>;
 
 			trips {
-				trip0: cpu-alert0 {
-					/* start throttling at 60C */
-					temperature = <60000>;
+				trip2: cpu-alert {
+					/* throttle at 85C until temperature drops to 84.8C */
+					temperature = <85000>;
 					hysteresis = <200>;
 					type = "passive";
 				};
 
-				trip1: cpu-crit {
-					/* shut down at 70C */
-					temperature = <70000>;
+				trip3: cpu-crit {
+					/* shut down at 90C */
+					temperature = <90000>;
 					hysteresis = <2000>;
 					type = "critical";
 				};
 			};
 
 			cooling-maps {
-				map0 {
-					trip = <&trip0>;
+				map1 {
+					trip = <&trip2>;
 					cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
 							 <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
 				};