On Thu, Jul 17, 2014 at 10:35 PM, Viresh Kumar viresh.kumar@linaro.org wrote:
Clock lines may or may not be shared among different CPUs on a platform. When clock lines are shared between CPUs, they change DVFS state together.
Possible configurations:
1.) All CPUs share a single clock line. 2.) All CPUs have independent clock lines. 3.) CPUs within a group/cluster share clock line but each group/cluster have a separate line for itself.
There is no generic way available today to detect which CPUs share clock lines and so this is an attempt towards that.
Much of the information is present in the commit and so no point duplicating it here.
These are obviously not finalized yet and this is an attempt to initiate a discussion around this.
Please share your valuable feedback.
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org
I wasn't sure about the path/name of this file, so please don't blast me on that :)
.../devicetree/bindings/cpufreq/cpu_clocks.txt | 159 +++++++++++++++++++++ 1 file changed, 159 insertions(+) create mode 100644 Documentation/devicetree/bindings/cpufreq/cpu_clocks.txt
diff --git a/Documentation/devicetree/bindings/cpufreq/cpu_clocks.txt b/Documentation/devicetree/bindings/cpufreq/cpu_clocks.txt new file mode 100644 index 0000000..30ce9ad --- /dev/null +++ b/Documentation/devicetree/bindings/cpufreq/cpu_clocks.txt @@ -0,0 +1,159 @@ +* Generic CPUFreq clock bindings
+Clock lines may or may not be shared among different CPUs on a platform.
+Possible configurations: +1.) All CPUs share a single clock line +2.) All CPUs have independent clock lines +3.) CPUs within a group/cluster share clock line but each group/cluster have a
- separate line for itself
+Optional Properties: +- clock-master: This declares cpu as clock master. Other CPUs can either define
- "clock-ganged" or "clock-master" property, but shouldn't be missing both.
+- clock-ganged: Should have phandle of a cpu declared as "clock-master".
Why complicate it by using two properties?
If there is no property, then the CPUs are assumed to be controlled independently.
if there is a clock-master = <phandle> property, then that points at the cpu that is the main one controlling clock for the group.
There's really no need to label the master -- it will be the only one with incoming links but nothing outgoing. And a master without slaves is an independently controlled cpu so you should be fine in that aspect too.
-Olof