linux-kernel - Re: [PATCH v3] PM / devfreq: Add possible

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Date:	Thu, 17 Jul 2014 20:32:54 -0700
From:	Saravana Kannan <skannan@...eaurora.org>
To:	myungjoo.ham@...sung.com
CC:	박경민 <kyungmin.park@...sung.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3] PM / devfreq: Add possible_frequencies device attribute

On 07/16/2014 05:50 PM, MyungJoo Ham wrote:
> On Wed, Jul 16, 2014 at 12:01 PM, Saravana Kannan <skannan@...eaurora.org> wrote:
>> Some devices use freq_table instead of OPP. For those devices, the
>> available_frequencies sysfs file shows up empty. So, add a
>> possible_frequencies attribute/syfs file that list all the possible
>> frequencies.
>>
>> For devices that use OPP, the output of this file will match
>> available_frequencies. It may change in the future to show all OPP
>> frequencies -- even the disabled ones.
>>
>> Signed-off-by: Saravana Kannan <skannan@...eaurora.org>
> 
> Hi,
> 
> 
> Please add a documentation entry for this new ABI having a little justification and usage included.

Will do.

> 
> Plus, I am considering to move trans_stat along with this entry to somewhere such as .../stat/*
> (you don't need to take care of this.)

Ok.

> 
> Besides, as OPP seems becoming the standard as imagined when devfreq development started,
> soon, devfreq may require OPP unless the devfreq device has continuous frequencies.

I agree. Only one caveat with OPP is that if a device isn't using OPP to
do any voltage scaling, then it forces a voltage column with 0s. Also,
even if we make OPP mandatory, we'll still want trans_stats that
currently seem to depend on freq_table being populated. I was actually
planning on sending out more patches later that'll do a lot of stuff
automatically for devices with OPP. Like creating freq_table, etc.

-Saravana

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