linux-kernel - Re: [PATCH v4 1/3] devicetree: bindings: Add optional dynamic-power-coefficient property

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Message-ID: <CAOh2x==3i-ksVOArpGJFVBH9jQspB4gN5u-uVi2XbT0HK5AoAQ@mail.gmail.com>
Date:	Tue, 17 Nov 2015 10:06:32 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Punit Agrawal <punit.agrawal@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Eduardo Valentin <edubezval@...il.com>,
	dawei.chien@...iatek.com, Javi Merino <javi.merino@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v4 1/3] devicetree: bindings: Add optional
 dynamic-power-coefficient property

On Tue, Nov 17, 2015 at 1:00 AM, Punit Agrawal <punit.agrawal@....com> wrote:
> The dynamic power consumption of a device is proportional to the
> square of voltage (V) and the clock frequency (f). It can be expressed as
>
> Pdyn = dynamic-power-coefficient * V^2 * f.
>
> The coefficient represents the running time dynamic power consumption in
> units of mw/MHz/uVolt^2 and can be used in the above formula to
> calculate the dynamic power in mW.
>
> Signed-off-by: Punit Agrawal <punit.agrawal@....com>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> ---
>  Documentation/devicetree/bindings/arm/cpus.txt | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt
> index 3a07a87..6aca64f 100644
> --- a/Documentation/devicetree/bindings/arm/cpus.txt
> +++ b/Documentation/devicetree/bindings/arm/cpus.txt
> @@ -242,6 +242,23 @@ nodes to be present and contain the properties described below.
>                 Definition: Specifies the syscon node controlling the cpu core
>                             power domains.
>
> +       - dynamic-power-coefficient
> +               Usage: optional
> +               Value type: <prop-encoded-array>
> +               Definition: A u32 value that represents the running time dynamic
> +                           power coefficient in units of mW/MHz/uVolt^2. The
> +                           coefficient can either be calculated from power
> +                           measurements or derived by analysis.
> +
> +                           The dynamic power consumption of the CPU  is
> +                           proportional to the square of the Voltage (V) and
> +                           the clock frequency (f). The coefficient is used to
> +                           calculate the dynamic power as below -
> +
> +                           Pdyn = dynamic-power-coefficient * V^2 * f
> +
> +                           where voltage is in uV, frequency is in MHz.
> +
>  Example 1 (dual-cluster big.LITTLE system 32-bit):
>
>         cpus {

Reviewed-by: Viresh Kumar <viresh.kumar@...aro.org>
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