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

[Tomasz Figa <t.figa@samsung.com>]

On 25.08.2014 17:32, Kevin Hilman wrote:
> Hi Chander,
> 
> Chander Kashyap <k.chander@samsung.com> writes:
> 
> [...]
> 
>>>> 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.
> 
> Can you clarify how you're setting the voltages to ensure stability?
> 
> Tomasz, I didn't mean to suggest this isn't ready for mainline.

I haven't said that either. I'd just like to know in what state this
series is in case of those SoCs. However, if there are stability issues
on them, there is also a chance that the same is true for other boards.

Anyway, we're early in releasy cycle, so probably we could get better
test coverage with this series in linux-next.

Kukjin, Viresh, how would you want to proceed with merging it? It
touches mach-exynos, cpufreq and samsung-clk, so it is non-trivial to
merge. However as far as I can see the cpufreq-related changes are just
a number of full file deletes and minor Makefile/Kconfig updates. It
will be more difficult with mach-exynos changes, as they are more likely
to produce conflict.

The only solution that comes to my mind is that I first apply patches 1
and 2, create a stable branch for Kukjin, then he applies patches 3, 4,
and 5 and creates a stable branch for me, on top of which I apply patch 6.

Best regards,
Tomasz