Re: Question about Odroid XU4 cpuidle

[Lukasz Luba <lukasz.luba@arm.com>]

On 6/15/20 1:45 PM, Marek Szyprowski wrote:
> Hi Lukasz
> 
> On 10.06.2020 16:30, Lukasz Luba wrote:
>> On 6/10/20 3:09 PM, Marek Szyprowski wrote:
>>> On 10.06.2020 16:02, Krzysztof Kozlowski wrote:
>>>> On Wed, Jun 10, 2020 at 02:18:12PM +0100, Lukasz Luba wrote:
>>>>> Hi Krzysztof, Bartek,
>>>>>
>>>>> I recall that you have been working on some cpuidle code for
>>>>> Exynos(4?).
>>>>>
>>>>> I have a question regarding CPUIdle driver for Odroid XU4.
>>>>> I use the board with LISA tests for EAS, but missing at
>>>>> least idle state 0 cause errors (please see the log below).
>>>>>
>>>>> Currently the system does not report any idle driver and the state 0
>>>>> is missing in: /sys/devices/system/cpu/cpu0/cpuidle/state0/
>>>> The state 0 long time ago was WFI. It was kind of meaningless so it it
>>>> was dropped.
>>>>
>>>>> I am using driver CONFIG_ARM_BIG_LITTLE_CPUIDLE but the
>>>>> boot stops silently while trying to init the cpu idle devices in
>>>>> there.
>>>>> I carry on with a workaround that just removes idle state[1] and set
>>>>> state_count=1 in the big and little structures.
>>>> Try earlyprintk.
>>>>
>>>> In general, the big-little cpuidle driver should work... or rather:
>>>> long
>>>> time ago it was working.  It requires proper support from early stages
>>>> (BL1, secure monitor) but this should be already in standard Odroid.
>>>>
>>>> I just saw there:
>>>>      /* Start at index 1, index 0 standard WFI */
>>>> so maybe it was not updated properly to removal of WFI?
>>>>
>>>> I think no one uses this driver so it might be not well tested and not
>>>> that useful.
>>>
>>> I think it never worked on Odroid XU3/XU4. Afair it was developed on
>>> PeachPi Chromebook, which use different bootloader (and doesn't use
>>> trustzone).
>>
>> That would explain the compatibility string in that driver. Good to
>> know. Thank you for your response.
>>
> I've just digged a bit in the old kernels and indeed, the big-little
> cpuidle driver worked only on Samsung Exynos 5420/5800 Chromebooks
> (Peach Pit/Pi). The last release which worked fine (although it was
> still not enabled in the exynos_defconfig) is v4.2. Then it got broken
> by the commit 833b5794e330 ("ARM: EXYNOS: reset Little cores when cpu is
> up"). It never worked on the Odroid XU3/XU4.

Thank you Marek for your time to investigate it. In this case I think
there is no way to fix idle state 1 for Odroid xu3/xu4. I don't have
Peach Pit/Pi so I have to pass, but I can help you in reviewing
if you or someone else have time (and board) to work on it.

> 
> Do you have any plans to fix it?

I'm baking some patch internally which might help Odroid XU3/4 though.
If that won't be killed, I'll post it soon.
If failed internally, I will also let you know.

Regards,
Lukasz

> 
> Best regards
>