linux-kernel - Re: [PATCH 1/3] PM / OPP: Add "opp-supported-hw" binding

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Date:	Fri, 30 Oct 2015 14:49:07 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Rafael Wysocki <rjw@...ysocki.net>, robh+dt@...nel.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,
	open list <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 1/3] PM / OPP: Add "opp-supported-hw" binding

On 10/30, Viresh Kumar wrote:
> +- opp-supported-hw: 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.

I suppose if you wanted to have 64 possible combinations of some
attribute you would just extend it to two 32 bit numbers in
sequence? I don't see the limitation here, and hopefully there
isn't a limitation so that we can specify sufficiently large
numbers with more bits if we need to.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
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