Re: [PATCHv2] ARM: EXYNOS: reset Little cores when cpu is up

[Javier Martinez Canillas <javier@osg.samsung.com>]

Hello Krzysztof,

On 09/02/2015 02:15 AM, Krzysztof Kozlowski wrote:
> On 01.09.2015 23:17, Chanho Park wrote:
>> The cpu booting of exynos5422 has been still broken since we discussed
>> it in last year[1]. This patch is inspired from Odroid XU3
>> code (Actually, it was from samsung exynos vendor kernel)[2]. This weird
>> reset code was founded exynos5420 octa cores series SoCs and only
>> required for the first boot core is the Little core (Cortex A7).
>> Some of the exynos5420 boards and all of the exynos5422 boards will require
>> this code.
>>
>> There is two ways to check the little core is the first cpu. One is
>> checking GPG2CON[1] GPIO value and the other is checking the cluster
>> number of the first cpu. I selected the latter because it's more easier
>> than the former.
>>
>> [1]:http://lists.infradead.org/pipermail/linux-arm-kernel/2015-June/350632.html
>> [2]:https://patchwork.kernel.org/patch/6782891/
>>
>> Cc: Kevin Hilman <khilman@kernel.org>
>> Cc: Javier Martinez Canillas <javier@osg.samsung.com>
>> Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
>> Tested-by: Kevin Hilman <khilman@linaro.org>
>> Signed-off-by: Chanho Park <parkch98@gmail.com>
>> ---
>> Changes from v1:
>>  .kfc to Little (Cortex A7) and eagle to big (Cortex A15)
>>  .append comments about waiting SPARE2 register
>>
>> Changes since RFC:
>>  .drop checking soc_is_exynos5800 to extend this codes to
>> exynos5420/5422 boards.
>>  .kfc cores will be reset only if the cpu0 is kfc core.
>>  .Rebase top of the kukjin's for-next branch
>>
>>  arch/arm/mach-exynos/mcpm-exynos.c | 25 ++++++++++++++++++++++++-
>>  arch/arm/mach-exynos/regs-pmu.h    |  6 ++++++
>>  2 files changed, 30 insertions(+), 1 deletion(-)
> 
> Thanks for updating the patch. Remaining minor nit about comment style
> (/* on first line) can be fixed while applying.
> 
> The patch works good, after disabling bL switcher I have 8 cores running:
> 
> Tested on Odroid XU4:
> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> Tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> 
> It's 4.3 merge window so the patch will go probably to v4.4.
> 

Isn't this material for the v4.3 -rc cycle since it's fixing a bug
(CPUs not booting)? So I don't think that's necessary to wait for v4.4.

But I was expecting another re-spin as from Abhilash's latest comments [0],
it seems the same workaround is needed in arch/arm/mach-exynos/platsmp.c
to avoid the CPU's not booting issue when CCI is disabled in DT and the
MCPM backend is bypassed.

Although I guess that could be also made as a follow up patch.

> Best regards,
> Krzysztof
> 
> 

[0]: http://www.spinics.net/lists/arm-kernel/msg442399.html

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America