linux-kernel - Re: [PATCH V2 1/5] PM / OPP: Add "opp-supported-hw" binding

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Message-ID: <20151105025729.GA13149@rob-hp-laptop>
Date:	Wed, 4 Nov 2015 20:57:29 -0600
From:	Rob Herring <robh@...nel.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Rafael Wysocki <rjw@...ysocki.net>, robh+dt@...nel.org,
	sboyd@...eaurora.org, lee.jones@...aro.org,
	linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
	mark.rutland@....com, pawel.moll@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org, nm@...com,
	devicetree@...r.kernel.org, b.zolnierkie@...sung.com,
	m.szyprowski@...sung.com, open list <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH V2 1/5] PM / OPP: Add "opp-supported-hw" binding

On Thu, Nov 05, 2015 at 07:11:52AM +0530, Viresh Kumar wrote:
> 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.
> 
> Reviewed-by: Stephen Boyd <sboyd@...eaurora.org>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>

Acked-by: Rob Herring <robh@...nel.org>

> ---
>  Documentation/devicetree/bindings/opp/opp.txt | 65 +++++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
> 
> 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 @@ 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
> +  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
> +  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.
> +
>  - status: Marks the node enabled/disabled.
>  
>  Example 1: Single cluster Dual-core ARM cortex A9, switch DVFS states together.
> @@ -463,3 +483,48 @@ Example 5: Multiple OPP tables
>  		};
>  	};
>  };
> +
> +Example 6: opp-supported-hw
> +(example: three level hierarchy of versions: cuts, substrate and process)
> +
> +/ {
> +	cpus {
> +		cpu@0 {
> +			compatible = "arm,cortex-a7";
> +			...
> +
> +			cpu-supply = <&cpu_supply>
> +			operating-points-v2 = <&cpu0_opp_table_slow>;
> +		};
> +	};
> +
> +	opp_table {
> +		compatible = "operating-points-v2";
> +		status = "okay";
> +		opp-shared;
> +
> +		opp00 {
> +			/*
> +			 * Supports all substrate and process versions for 0xF
> +			 * cuts, i.e. only first four cuts.
> +			 */
> +			opp-supported-hw = <0xF 0xFFFFFFFF 0xFFFFFFFF>
> +			opp-hz = /bits/ 64 <600000000>;
> +			opp-microvolt = <900000 915000 925000>;
> +			...
> +		};
> +
> +		opp01 {
> +			/*
> +			 * Supports:
> +			 * - cuts: only one, 6th cut (represented by 6th bit).
> +			 * - substrate: supports 16 different substrate versions
> +			 * - process: supports 9 different process versions
> +			 */
> +			opp-supported-hw = <0x20 0xff0000ff 0x0000f4f0>
> +			opp-hz = /bits/ 64 <800000000>;
> +			opp-microvolt = <900000 915000 925000>;
> +			...
> +		};
> +	};
> +};
> -- 
> 2.6.2.198.g614a2ac
> 
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