Date:	Mon, 14 Sep 2015 15:22:47 -0500
From:	Rob Herring <robh@...nel.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>,
	Rafael Wysocki <rjw@...ysocki.net>, nm@...com,
	sboyd@...eaurora.org
Cc:	linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
	rob.herring@...aro.org, lee.jones@...aro.org,
	Mark Brown <broonie@...nel.org>, devicetree@...r.kernel.org,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	open list <linux-kernel@...r.kernel.org>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 01/16] PM / OPP: Add 'supply-names' binding

On 09/11/2015 07:01 AM, Viresh Kumar wrote:
> Regulators already have stable DT bindings, wherein the consumer (of
> supplies) will have following for each regulator/supply.
> 
> <name>-supply: <phandle to the regulator node>;
> 
> Current OPP bindings extend above, by transforming it into a list of
> phandles. But we missed the <name> string, which is used to identify the
> regulator.
> 
> And looking from regulators perspective, having two different ways of
> specifying regulators doesn't seem like a step forward, it also means we
> have to update every single device binding. And things will become
> complex.
> 
> Another way to support multiple regulators per device (in OPP V2
> bindings) is to leave regulator consumer bindings as is, and create a
> 'supply-names' property in the opp-table node, which will contain a list
> of strings. The names in this list shall match 'name' from the
> '<name>-supply' strings present in the device node.
> 
> The strings in this list also specify the order in which values must be
> present in 'opp-microvolt' and 'opp-microamp' properties.
> 
> Cc: Mark Brown <broonie@...nel.org>
> Cc: devicetree@...r.kernel.org
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  Documentation/devicetree/bindings/opp/opp.txt | 26 +++++++++++++++++++-------
>  1 file changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
> index 0cb44dc21f97..8759bc4783ed 100644
> --- a/Documentation/devicetree/bindings/opp/opp.txt
> +++ b/Documentation/devicetree/bindings/opp/opp.txt
> @@ -69,6 +69,13 @@ This describes the OPPs belonging to a device. This node can have following
>  - compatible: Allow OPPs to express their compatibility. It should be:
>    "operating-points-v2".
>  
> +- supply-names: This is a required property, only if multiple supplies are
> +  available for the device. Otherwise it is optional.
> +
> +  This list is used to pass names of all the device supplies. The order of names
> +  present here is important, as that should match the order in which values are
> +  present in 'opp-microvolt' and 'opp-microamp' properties.
> +

What if we have a 2nd device and supply rail? For example, what if the
L2$ has a separate rail from the cores but is linked to the OPPs.

>  - OPP nodes: One or more OPP nodes describing voltage-current-frequency
>    combinations. Their name isn't significant but their phandle can be used to
>    reference an OPP.
> @@ -97,8 +104,8 @@ properties.
>    Single entry is for target voltage and three entries are for <target min max>
>    voltages.
>  
> -  Entries for multiple regulators must be present in the same order as
> -  regulators are specified in device's DT node.
> +  Entries for multiple regulators must be present in the same order as their
> +  names are present in 'supply-names' property of the opp-table.
>  
>  - opp-microamp: The maximum current drawn by the device in microamperes
>    considering system specific parameters (such as transients, process, aging,
> @@ -107,10 +114,12 @@ properties.
>  
>    Should only be set if opp-microvolt is set for the OPP.
>  
> -  Entries for multiple regulators must be present in the same order as
> -  regulators are specified in device's DT node. If this property isn't required
> -  for few regulators, then this should be marked as zero for them. If it isn't
> -  required for any regulator, then this property need not be present.
> +  Entries for multiple regulators must be present in the same order as their
> +  names are present in 'supply-names' property of the opp-table.
> +
> +  If this property isn't required for few regulators, then this should be marked
> +  as zero for them. If it isn't required for any regulator, then this property
> +  need not be present.

Remind me of when do we have multiple regulators for a cpu? The number
of supplies should be defined by the cpu binding as function of how many
supply rails a cpu has.

>  
>  - clock-latency-ns: Specifies the maximum possible transition latency (in
>    nanoseconds) for switching to this OPP from any other OPP.
> @@ -369,13 +378,16 @@ Example 4: Handling multiple regulators
>  			compatible = "arm,cortex-a7";
>  			...
>  
> -			cpu-supply = <&cpu_supply0>, <&cpu_supply1>, <&cpu_supply2>;
> +			vcc0-supply = <&cpu_supply0>;
> +			vcc1-supply = <&cpu_supply1>;
> +			vcc2-supply = <&cpu_supply2>;

This may just be an example, but a CA7 doesn't have 3 supply rails.

Rob

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