Re: [cip-dev] [PATCH 4.4.y-cip 1/3] PM / OPP: Add "opp-supported-hw" binding

[Pavel Machek <pavel@denx.de>]

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Hi!

> From: Viresh Kumar <viresh.kumar@linaro.org>
> 
> commit 1c4d12de2719dfdf27c6dab31e7a5641ee293c94 upstream
> 
> We may want to enable only a subset of OPPs, from the bigger list of
> OPPs, based on what version of the hardware we are running on. This
> would enable us to not duplicate OPP tables for every version of the
> hardware we support.
> 
> To enable that, this patch defines a new property 'opp-supported-hw'. It
> can support any number of hierarchy levels of the versions the hardware
> follows. And based on the selected hardware versions, we can pick only
> the relevant OPPs at runtime.

Few typos mentioned below, but this should not block merge.

> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
> index 0cb44dc21f97..d072fa0ffbd4 100644
> --- a/Documentation/devicetree/bindings/opp/opp.txt
> +++ b/Documentation/devicetree/bindings/opp/opp.txt
> @@ -123,6 +123,26 @@ Optional properties:
>  - opp-suspend: Marks the OPP to be used during device suspend. Only one OPP in
>    the table should have this.
>  
> +- opp-supported-hw: This enables us to select only a subset of OPPs from the
> +  larger OPP table, based on what version of the hardware we are running on. We
> +  still can't have multiple nodes with the same opp-hz value in OPP table.
> +
> +  It's an user defined array containing a hierarchy of hardware version numbers,
> +  supported by the OPP. For example: a platform with hierarchy of three levels
> +  of versions (A, B and C), this field should be like <X Y Z>, where X
> +  corresponds to Version hierarchy A, Y corresponds to version hierarchy B and Z

"Version->version".

> +  corresponds to version hierarchy C.
> +
> +  Each level of hierarchy is represented by a 32 bit value, and so there can be
> +  only 32 different supported version per hierarchy. i.e. 1 bit per version. A

"supported versions".

> +  value of 0xFFFFFFFF will enable the OPP for all versions for that hierarchy
> +  level. And a value of 0x00000000 will disable the OPP completely, and so we
> +  never want that to happen.

> +  If 32 values aren't sufficient for a version hierarchy, than that version
> +  hierarchy can be contained in multiple 32 bit values. i.e. <X Y Z1 Z2> in the
> +  above example, Z1 & Z2 refer to the version hierarchy Z.

Above it claims that there can be only 32 versions, then it explains
how to do more than 32 versions. Overall, I find this text rather
confusing (concept is quite simple, but I'd not understand it without
the example).

Best regards,
								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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