linux-kernel - Re: [RFC v2 0/4] Add basic support for ASV

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Message-ID: <CAM4voak0QaseYoRM+rsx2Fa8qs1z=w9iVep1smxx73_SUhmkJQ@mail.gmail.com>
Date:	Tue, 3 Dec 2013 20:16:12 +0530
From:	Abhilash Kesavan <kesavan.abhilash@...il.com>
To:	Sachin Kamat <sachin.kamat@...aro.org>
Cc:	MyungJoo Ham <myungjoo.ham@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	Yadwinder Singh Brar <yadi.brar01@...il.com>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Bresticker <abrestic@...gle.com>,
	Doug Anderson <dianders@...gle.com>
Subject: Re: [RFC v2 0/4] Add basic support for ASV

Hi Yadwinder and Sachin,

On Mon, Nov 18, 2013 at 9:37 AM, Sachin Kamat <sachin.kamat@...aro.org> wrote:
> Hi MyungJoo,
>
> On 18 November 2013 08:07, MyungJoo Ham <myungjoo.ham@...sung.com> wrote:
>>
>> 2013. 11. 15. 오후 8:44에 "Sachin Kamat" <sachin.kamat@...aro.org>님이 작성:
>>
>>
>>>
>>> Original cover letter from Yadwinder:
>>> This series is to add basic common infrastructure for ASV.
>>>  Basically ASV is a technique used on samsung SoCs, which provides the
>>> recommended supply voltage for dvfs of arm, mif etc. For a given operating
>>> frequency, the voltage is recommended based on SoC's ASV group.
>>> ASV group gets fussed on SoCs during process of mass production.
>>>
>>> This series includes:
>>>  - basic common infrastructue for ASV. It provides common APIs for user
>>> drivers
>>> like cpufreq & devfreq and and an interface for SoC specific drivers to
>>> register ASV members(instances)
>>>  - a common platform driver to register ASV members for exynos SoCs
>>>  - an example providing minimal support (only for ARM ASV) for exynos5250
>>> chips
>>>
>>> Its just basic skelton which I wanted to get it reviewed or discussed in
>>> early stage, before going ahead on further development based on it.
>>>  Presently example is based on static ASV table provided in SoC specific
>>> file,
>>> which I expects to go into DT. But exactly how and where needs to be
>>> discussed,
>>> may be in next revisions once we get through the basic skelton.
>>>  Also the location of driver in kernel may also seem odd to someone and
>>> many more things :).
>>>
>>> Looking for your valuable reviews and suggestions.
>>
>> Hi,
>>
>> As I have commented on the previous thread of Yadwinder, please share the
>> directory woth AVS, which is conceptually a superset of ASV.
>>
>> Ultimately, it would be best if you can supply an infra that can be shared
>> with the current AVS, which does not have any currently.
>>
>
> Yadwinder has already replied to your suggestion about his concerns. Please
> share your comments.
>

CC'ing Doug and Andrew who have also worked on ASV.

I tested these patches on a 5250 Chromebook after modifying the
cpufreq code and a few other changes for booting the board. The driver
is retrieving the ASV fused group correctly. The behavior on an
unfused SMDK5250 is also fine.
I have a few minor comments on the patches.

Thanks
Abhilash
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