OPP: Introduce "required-opp" property

Devices have inter-dependencies some times. For example a device that
needs to run at 800 MHz, needs another device (e.g. Its power domain) to
be configured at a particular operating performance point.

This patch introduces a new property "required-opp" which can be present
directly in a device's node (if it doesn't need to change its OPPs), or
in device's OPP nodes. More details on the property can be seen in the
binding itself.

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
index a3953a1bb1a1..4e4f30288c8b 100644
--- a/Documentation/devicetree/bindings/opp/opp.txt
+++ b/Documentation/devicetree/bindings/opp/opp.txt
@@ -159,6 +159,14 @@ Optional properties:
 
 - status: Marks the node enabled/disabled.
 
+- required-opp: This contains phandle to an OPP node in another device's OPP
+  table. It may contain an array of phandles, where each phandle points to an
+  OPP of a different device. It should not contain multiple phandles to the OPP
+  nodes in the same OPP table. This specifies the minimum required OPP of the
+  device(s), whose OPP's phandle is present in this property, for the
+  functioning of the current device at the current OPP (where this property is
+  present).
+
 Example 1: Single cluster Dual-core ARM cortex A9, switch DVFS states together.
 
 / {