Re: CPUIdle for Exynos5422 Odroid-XU3/XU4 boards.

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

[Adding Przemyslaw Marczak who was working on porting Odroid BL1/BL2/SPL]

Hello,

On 08/21/2015 05:59 AM, Krzysztof Kozlowski wrote:
> On 21.08.2015 12:41, Anand Moon wrote:
>> Hi Krzysztof,
>>
>> On 21 August 2015 at 06:25, Krzysztof Kozlowski <k.kozlowski@samsung.com> wrote:
>>> On 21.08.2015 03:15, Anand Moon wrote:
>>>> Hi Daniel,
>>>>
>>>> On 20 August 2015 at 21:40, Daniel Lezcano <daniel.lezcano@free.fr> wrote:
>>>>> On 08/20/2015 12:54 PM, Anand Moon wrote:
>>>>>>
>>>>>> Hello Krzysztof/Kukjim,
>>>>>>
>>>>>> CPUIdle seen to be not working for Exynos5422 Odroid boards.
>>>>>>
>>>>>> Is their any way this feature will be implemented in the future.
>>>>>
>>>>>
>>>>> Yeah a good willing to fix the bl1. More than one year asking for that !
>>>>> nooo way !!
>>>>>
>>>>> Your answer is at the end of
>>>>> http://lists.infradead.org/pipermail/linux-arm-kernel/2015-June/350632.html
>>>>>
>>>>>
>>>>
>>>> Thanks for the explanation.
>>>>
>>>> I was just referring following the source code.
>>>>
>>>> https://github.com/hardkernel/linux/blob/odroidxu3-3.10.y/arch/arm/mach-exynos/cpuidle-exynos5422.c
>>>>
>>>> It seem that cpufreq and cpuidle go hand in hand.
>>>
>>> Bartlomiej was working on cpufreq for Exynos542x:
>>> http://lkml.iu.edu/hypermail/linux/kernel/1504.2/03139.html
>>>
>>> It would be nice to have also cpuidle and suspend features working on
>>> Exynos542x family but this depends on firmware. Some time ago I
>>> struggled with suspend on Arndale Octa (Exynos5420) and I failed. I
>>> think the firmware is the issue here.

There were a lot of Suspend-to-RAM bug fixes lately mostly related to
critical clocks being gated. It would be nice to give a try on recent
kernels and see if is still not working.

>>>
>>> Actually I am not sure what is your question Anand. You are asking if
>>> someone plans to do this?
>>
>> Yes I am asking are their plans to implement cpufreq and cpuidle simultaneously.
> 
> There are no obstacles for implementing them simultaneously so the
> question is rather who plans to do the cpuidle driver for Exynos542x? I

If the firmware is in a good shape (unfortunately as mentioned by Daniel,
the one in the Odroids are not) then the generic ARM big.LITTLE CPUidle
driver (CONFIG_ARM_BIG_LITTLE_CPUIDLE) should work.

It is at least working for me on the Exynos5800 based Peach Pi Chromebook:

$ cat /sys/devices/system/cpu/cpuidle/current_driver
big_idle

$ cat /sys/devices/system/cpu/cpu0/cpuidle/state*/name
WFI
C1

$ cat /sys/devices/system/cpu/cpu0/cpuidle/state*/usage
7745
10578

> don't... at least in nearby future. If I had some spare time then
> probably I would try to make suspend working.
>

Suspend-to-RAM is at least working on the Exynos5420 and Exynos5800
Chromebooks.

As you mentioned it may depend on the firmware so that does not hold
true for all the Exynos5420/5422/5800 boards but it would be good to
know what is the causing S2R to fail.

> Best regards,
> Krzysztof
> 

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