[PATCH V4 2/3] OPP: Allow multiple OPP tables to be passed via DT

Nishanth Menon nm at ti.com
Tue May 12 09:09:04 PDT 2015

On 04/30/2015 07:08 AM, Viresh Kumar wrote:
> On some platforms (Like Qualcomm's SoCs), it is not decided until
> runtime on what OPPs to use. The OPP tables can be fixed at compile
> time, but which table to use is found out only after reading some efuses
> (sort of an eeprom) and knowing characteristics of the SoC.

they are more like prom than eeprom in many instances.

> To support such platform we need to pass multiple OPP tables per device
> and hardware should be able to choose one and only one table out of
> those.
> Update OPP-v2 bindings to support that.
> Signed-off-by: Viresh Kumar <viresh.kumar at linaro.org>
> ---
>  Documentation/devicetree/bindings/power/opp.txt | 5 +++++
>  1 file changed, 5 insertions(+)
> diff --git a/Documentation/devicetree/bindings/power/opp.txt b/Documentation/devicetree/bindings/power/opp.txt
> index 3b67a5c8d965..07959903ec32 100644
> --- a/Documentation/devicetree/bindings/power/opp.txt
> +++ b/Documentation/devicetree/bindings/power/opp.txt
> @@ -14,6 +14,9 @@ Devices supporting OPPs must set their "operating-points-v2" property with
>  phandle to a OPP descriptor in their DT node. The OPP core will use this phandle
>  to find the operating points for the device.
> +Devices may want to choose OPP tables at runtime and so can provide a list of
> +phandles here. But only *one* of them should be chosen at runtime.
> +
>  * OPP Descriptor Node
> @@ -28,6 +31,8 @@ This describes the OPPs belonging to a device. This node can have following
>    reference an OPP.
>  Optional properties:
> +- opp-name: Name of the OPP table, to uniquely identify it if more than one OPP
> +  table is supplied in "operating-points-v2" property of device.
>  - shared-opp: Indicates that device nodes using this OPP descriptor's phandle
>    switch their DVFS state together, i.e. they share clock/voltage/current lines.
>    Missing property means devices have independent clock/voltage/current lines,

With some SoCs like AM335x - thanks to some brain dead incompatible
hardware design choices, this might end up as a big list or various
OPP tables. but overall, I must prefer this approach as well.

Thanks for proposing this. will be great to see examples documented in
bindings doc as well.

With no further issues,
Acked-by: Nishanth Menon <nm at ti.com>

Nishanth Menon

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