PM / OPP: Initialize OPP table from device tree

With a lot of devices booting from device tree nowadays, it requires
that OPP table can be initialized from device tree.  The patch adds
a helper function of_init_opp_table together with a binding doc for
that purpose.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 25 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/power/opp.txt b/Documentation/devicetree/bindings/power/opp.txt
new file mode 100644
index 000000000000..74499e5033fc
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/opp.txt
@@ -0,0 +1,25 @@
+* Generic OPP Interface
+
+SoCs have a standard set of tuples consisting of frequency and
+voltage pairs that the device will support per voltage domain. These
+are called Operating Performance Points or OPPs.
+
+Properties:
+- operating-points: An array of 2-tuples items, and each item consists
+  of frequency and voltage like <freq-kHz vol-uV>.
+        freq: clock frequency in kHz
+        vol: voltage in microvolt
+
+Examples:
+
+cpu@0 {
+        compatible = "arm,cortex-a9";
+        reg = <0>;
+        next-level-cache = <&L2>;
+        operating-points = <
+                /* kHz    uV */
+                792000  1100000
+                396000  950000
+                198000  850000
+        >;
+};