[PATCH v9 4/6] ARM: Exynos: switch to using generic cpufreq driver for Exynos4210/5250/5420

Chander Kashyap k.chander at samsung.com
Mon Aug 25 05:15:07 PDT 2014

Hi Kevin, Tomasz,

On Sat, Aug 23, 2014 at 5:32 AM, Tomasz Figa <tomasz.figa at gmail.com> wrote:
> Hi Kevin,
> Thanks for taking a look at this.
> On 23.08.2014 01:54, Kevin Hilman wrote:
>> Tomasz Figa <tomasz.figa at gmail.com> writes:
>>> Kukjin,
>>> On 31.07.2014 20:32, Kukjin Kim wrote:
>>>> On 07/30/14 17:07, Thomas Abraham wrote:
>>>>> The new CPU clock type allows the use of generic CPUfreq drivers. So for
>>>>> Exynos4210/5250, switch to using generic cpufreq driver. For Exynos5420,
>>>>> which did not have CPUfreq driver support, enable the use of generic
>>>>> CPUfreq driver.
>>>>> Suggested-by: Tomasz Figa<t.figa at samsung.com>
>>>>> Cc: Kukjin Kim<kgene.kim at samsung.com>
>>>> Looks good to me,
>>>> Acked-by: Kukjin Kim <kgene.kim at samsung.com>
>>>> BTW, who will handle this series? I hope see this series in 3.17.
>>> This series consists mostly of clock changes and it likely depends on
>>> patches already in my for-next, so I would be inclined toward taking it
>>> through samsung-clk tree.
>> So has this series been picked up anywhere?  I don't see it in your
>> samsung-clk tree, nor in Kukjin's for-next.
> No, it has not. In general it was already too late in the release cycle
> when the last version was posted.
> I had a plan to take it through clock tree with Kukjin's and Viresh's
> cooperation, but now as you say it...
>> Also, I'm curious whether or how this is has been tested on big.LITTLE
>> SoCs.
>> I'm trying it on the 5800/Chromebook2 and it's not terribly stable.  I'm
>> testing along with CPUidle, so there may be some untested interactions
>> there as it seems a bit more stable without CPUidle enabled.
>> I'd love to hear from anyone else that's testing CPUidle and CPUfreq
>> together big.LITTLE 5420/5800, with or without the switcher.

I have tested this patch series on SMDK5420 with cpuidle (with and
without b.L switcher enabled).

As of now voltage scaling support is not there in generic big-little
cpufreq driver (arm_big_little.c).
Hence need to tie arm and kfc voltages to highest level for testing.

Without this change stability issues are there, but with this change
everything is stable.

> I'd definitely like to see a clarification on this issues, before this
> series hits mainline or at least its parts related to affected SoCs.
> Also I'd like to hear some confirmation from Samsung Poland R&D Center
> guys (on CC), whether this code works stable on their target boards
> (Universal C210, Trats, Trats2).
>> Also, the patch below[2] is needed for 5800.
>> FWIW, I have a temporary branch[1] based on the v3.17-rc branch of the
>> exynos-reference tree where I've added the DT patch needed for CPUidle,
>> this series (and it's dependencies) which is what I'm using for testing.
> The patch looks fine to me (well, it's trivial :)), thanks.
> Best regards,
> Tomasz
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