ARM: tegra: nexus7: Improve thermal zones

Use skin temperature for maintaining temperature that is suitable
specifically for Nexus 7. 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: NDmitry Osipenko <digetx@gmail.com>
Signed-off-by: NThierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra30-asus-nexus7-grouper-common.dtsi

@@ -1255,21 +1255,34 @@
 	};
 
 	thermal-zones {
-		cpu-thermal {
+		/*
+		 * NCT72 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 Nexus 7
+		 * 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 = <5000>; /* milliseconds */
 
-			thermal-sensors = <&nct72 1>;
+			thermal-sensors = <&nct72 0>;
 
 			trips {
-				trip0: cpu-alert0 {
+				trip0: skin-alert {
 					/* throttle at 57C until temperature drops to 56.8C */
 					temperature = <57000>;
 					hysteresis = <200>;
 					type = "passive";
 				};
 
-				trip1: cpu-crit {
+				trip1: skin-crit {
 					/* shut down at 65C */
 					temperature = <65000>;
 					hysteresis = <2000>;
@@ -1289,5 +1302,40 @@
 				};
 			};
 		};
+
+		cpu-thermal {
+			polling-delay-passive = <1000>; /* milliseconds */
+			polling-delay = <5000>; /* milliseconds */
+
+			thermal-sensors = <&nct72 1>;
+
+			trips {
+				trip2: cpu-alert {
+					/* throttle at 85C until temperature drops to 84.8C */
+					temperature = <85000>;
+					hysteresis = <200>;
+					type = "passive";
+				};
+
+				trip3: cpu-crit {
+					/* shut down at 90C */
+					temperature = <90000>;
+					hysteresis = <2000>;
+					type = "critical";
+				};
+			};
+
+			cooling-maps {
+				map1 {
+					trip = <&trip2>;
+					cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
+							 <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
+							 <&cpu2 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
+							 <&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
+							 <&actmon THERMAL_NO_LIMIT
+								  THERMAL_NO_LIMIT>;
+				};
+			};
+		};
 	};
 };