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.
Do you have any plans to fix it?
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
