Re: [PATCH v3 2/2] Documentation: devicetree: Add boost-frequency binding to list boost mode frequency

[Sudeep Holla <sudeep.holla@arm.com>]

On 14/05/14 02:03, Thomas Abraham wrote:
> From: Thomas Abraham <thomas.ab@samsung.com>
>
> Add a new optional boost-frequency binding for specifying the frequencies
> usable in boost mode.
>
> Cc: Nishanth Menon <nm@ti.com>
> Cc: Lukasz Majewski <l.majewski@samsung.com>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Pawel Moll <pawel.moll@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
> Cc: Kumar Gala <galak@codeaurora.org>
> Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
> ---
>   .../devicetree/bindings/cpufreq/cpufreq-boost.txt  |   11 +++++++++++
>   1 files changed, 11 insertions(+), 0 deletions(-)
>   create mode 100644 Documentation/devicetree/bindings/cpufreq/cpufreq-boost.txt
>
> diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-boost.txt b/Documentation/devicetree/bindings/cpufreq/cpufreq-boost.txt
> new file mode 100644
> index 0000000..d925e38
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-boost.txt
> @@ -0,0 +1,11 @@
> +* Device tree binding for CPU boost frequency (aka over-clocking)
> +
> +Certain CPU's can be operated in optional 'boost' mode (or sometimes referred as
> +overclocking) in which the CPU can operate in frequencies beyond the normal
> +operating conditions.
> +
> +Optional Properties:
> +- boost-frequency: list of frequencies in KHz to be used only in boost mode.
> +  This list should be a subset of frequencies listed in "operating-points"
> +  property. Refer to Documentation/devicetree/bindings/power/opp.txt for
> +  details about "operating-points" property.
>

Though I understand the need of it, I think the binding is designed to suffice
the need of the boost frequency support in cpufreq.

Typically SoC would provide characteristics like under-drive(hits performance
but most energy efficient), nominal(highest sustained performance w/o any
external constraint like power, thermal) and over-drive(maximum performance but
not sustainable for long periods)

IMO the binding could represent these unique points on the curve instead.

Regards,
Sudeep