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

[Thomas Abraham]

Hi Kevin,

On Wed, Aug 27, 2014 at 3:55 AM, Kevin Hilman <khilman at linaro.org> wrote:
> On Tue, Aug 26, 2014 at 8:15 AM, Kevin Hilman <khilman at linaro.org> wrote:
>> On Mon, Aug 25, 2014 at 10:25 PM, Chander Kashyap <k.chander at samsung.com> wrote:
>
> [...]
>
>>>>
>>>> Can you clarify how you're setting the voltages to ensure stability?
>>>
>>> below is the diff :  wip/exynos/integ
>>
>> Thanks.
>>
>> I've applied your patch, and bootup shows vdd_arm and vdd_kfc at
>> 1500mV, but still when booting with cpuidle enabled (bL switcher
>> disabled), I'm seeing lockups with no kernel output.  With CPUidle
>> disabled, things are pretty stable.
>>
>> What tree are you using to test this out on 5420?  I'm using mainline
>> v3.17-rc1 + DT patch for CPUidle and this cpufreq series.  See my
>> wip/exynos/integ branch at
>> git://git.kernel.org/pub/scm/linux/kernel/git/khilman/linux.git.
>
> I mis-stated this.  Actually my tree is based on the v3.17-rc1 branch
> of the exynos-reference tree[1] + the above mentioned patches for
> cpuidle and cpufreq.
>
> Also, I've narrowed down the instability a bit, and it's not related
> to CPUidle.  I can now trigger a boot hang even without CPUidle
> enabled.  Here's a quick way to cause a boot lockup. With the switcher
> disabled, I enable CPUfreq and set the default governor to
> performance.  As soon as cpufreq driver loads, it tries to use the top
> frequences for both clusters, and it hangs.
>
> Selectively disabling frequencies, I narrowed it down to the 1.3GHz
> and 1.2GHz frequencies of the little cluster.  With these commented
> out in the DT, it will fully boot with the performance governor
> enabled.
>
> So that leads to the question.  Are all of the operating points in
> exynos5420.dtsi valid for exynos5800, and have they been validated?

I tried to recreate the boot lockup issue using the same steps you
listed above for the Exynos5800 peach-pi platform (Chromebook2), but I
do not see any issues. I can see both clusters with max clock speed
after boot (1.8GHz and 1.3GHz).

I am using v3.17-rc2 + CPUFreq Patches + max77802 regulator support
patches for Chromebook2 + temp hack to set A15 voltage to 1.35V and A7
voltage to 1.3V.

Sorry for the delaying in following up.

Thanks,
Thomas.

>
> Kevin
>
> [1]https://github.com/exynos-reference/kernel.git
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