linux-kernel - Re: [PATCH] cpufreq: ARM big LITTLE: Add generic cpufreq driver and its DT glue

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Date:	Wed, 6 Mar 2013 17:46:57 -0800
From:	Olof Johansson <olof@...om.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	rjw@...k.pl, cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, robin.randhawa@....com,
	Steve.Bannister@....com, Liviu.Dudau@....com,
	charles.garcia-tobin@....com, linaro-kernel@...ts.linaro.org,
	mark.hambleton@...adcom.com, linux-arm-kernel@...ts.infradead.org,
	Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
Subject: Re: [PATCH] cpufreq: ARM big LITTLE: Add generic cpufreq driver and
 its DT glue

On Tue, Mar 05, 2013 at 12:52:41PM +0800, Viresh Kumar wrote:
> +++ b/Documentation/devicetree/bindings/cpufreq/arm_big_little_dt.txt
> @@ -0,0 +1,29 @@
> +Generic ARM big LITTLE cpufreq driver's DT glue
> +-----------------------------------------------
> +
> +It is DT specific glue layer for generic cpufreq driver for big LITTLE systems.
> +
> +Both required and optional properties listed below must be defined under node
> +cluster*. * can be 0 or 1.
> +
> +Required properties:
> +- freqs: List of all supported frequencies.
> +
> +Optional properties:
> +- clock-latency: Specify the possible maximum transition latency for clock, in
> +  unit of nanoseconds.
> +
> +Examples:
> +
> +cluster0: cluster@0 {
> +        ..
> +
> +	freqs = <500000000 600000000 700000000 800000000 900000000 1000000000 1100000000 1200000000>;
> +	clock-latency = <200000>;
> +
> +	..
> +
> +        cores {
> +		..
> +        };
> +};

This binding makes no sense to me. It needs to be substantially better
documented, not just a couple of sentences that people that understand
bit.LITTLE thoroughly can make sense of.

It also duplicates the cpu binding. I suspect this should instead be done
through additions of the cpu bindings instead of duplication. So this needs to
be substantially reworked.


-Olof
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