PM / OPP: Add {opp-microvolt|opp-microamp}-<name> binding

Depending on the version of hardware or its properties, which are only
known at runtime, various properties of the OPP can change. For example,
an OPP with frequency 1.2 GHz, may have different voltage/current
requirements based on the version of the hardware it is running on.

In order to not replicate the same OPP tables for varying values of all
such fields, this commit introduces the concept of opp-property-<name>.
The <name> can be chosen by the platform at runtime, and OPPs will be
initialized depending on that name string. Currently support is extended
for the following properties:
- opp-microvolt-<name>
- opp-microamp-<name>

If the name string isn't provided by the platform, or if it is provided
but doesn't match the properties present in the OPP node, we will fall
back to the original properties without the -<name> string, if they are
available.
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/devicetree/bindings/opp/opp.txt

@@ -100,6 +100,14 @@ Optional properties:
   Entries for multiple regulators must be present in the same order as
   regulators are specified in device's DT node.
 
+- opp-microvolt-<name>: Named opp-microvolt property. This is exactly similar to
+  the above opp-microvolt property, but allows multiple voltage ranges to be
+  provided for the same OPP. At runtime, the platform can pick a <name> and
+  matching opp-microvolt-<name> property will be enabled for all OPPs. If the
+  platform doesn't pick a specific <name> or the <name> doesn't match with any
+  opp-microvolt-<name> properties, then opp-microvolt property shall be used, if
+  present.
+
 - opp-microamp: The maximum current drawn by the device in microamperes
   considering system specific parameters (such as transients, process, aging,
   maximum operating temperature range etc.) as necessary. This may be used to
@@ -112,6 +120,9 @@ Optional properties:
   for few regulators, then this should be marked as zero for them. If it isn't
   required for any regulator, then this property need not be present.
 
+- opp-microamp-<name>: Named opp-microamp property. Similar to
+  opp-microvolt-<name> property, but for microamp instead.
+
 - clock-latency-ns: Specifies the maximum possible transition latency (in
   nanoseconds) for switching to this OPP from any other OPP.
 
@@ -528,3 +539,39 @@ Example 6: opp-supported-hw
 		};
 	};
 };
+
+Example 7: opp-microvolt-<name>, opp-microamp-<name>:
+(example: device with two possible microvolt ranges: slow and fast)
+
+/ {
+	cpus {
+		cpu@0 {
+			compatible = "arm,cortex-a7";
+			...
+
+			operating-points-v2 = <&cpu0_opp_table>;
+		};
+	};
+
+	cpu0_opp_table: opp_table0 {
+		compatible = "operating-points-v2";
+		opp-shared;
+
+		opp00 {
+			opp-hz = /bits/ 64 <1000000000>;
+			opp-microvolt-slow = <900000 915000 925000>;
+			opp-microvolt-fast = <970000 975000 985000>;
+			opp-microamp-slow =  <70000>;
+			opp-microamp-fast =  <71000>;
+		};
+
+		opp01 {
+			opp-hz = /bits/ 64 <1200000000>;
+			opp-microvolt-slow = <900000 915000 925000>, /* Supply vcc0 */
+					      <910000 925000 935000>; /* Supply vcc1 */
+			opp-microvolt-fast = <970000 975000 985000>, /* Supply vcc0 */
+					     <960000 965000 975000>; /* Supply vcc1 */
+			opp-microamp =  <70000>; /* Will be used for both slow/fast */
+		};
+	};
+};