Re: [PATCH 0/4] Restore big.LITTLE cpuidle driver for Exynos

Marek Szyprowski
2020-06-17T09:48:42Z

Hi Anand,

On 16.06.2020 22:58, Anand Moon wrote:
> On Tue, 16 Jun 2020 at 13:44, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
>> The ARM big.LITTLE cpuidle driver has been enabled and tested on Samsung
>> Exynos 5420/5800 based Peach Pit/Pi Chromebooks and in fact it worked
>> only on those boards.
>>
>> However, support for it was broken by the commit 833b5794e330 ("ARM:
>> EXYNOS: reset Little cores when cpu is up") and then never enabled in the
>> exynos_defconfig. This patchset provides the needed fix to the common
>> code and restores support for it. Thanks to Lukasz Luba who motivated me
>> to take a look into this issue.
>>
> Thanks for this updates.
>
> But I feel some DTS changes are missing for example
> d2e5c871ed8a drivers: cpuidle: initialize big.LITTLE driver through DT

This is not strictly needed. The bl-cpuidle matches also to the A7/A15
CPU product ids and it is properly instantiated on the Peach Pit/Pi
Chromebooks. Those CPU DT properties were added as a future-proof
generic solution. I won't hurt to add them though.

> But I feel that this feature is not working as desired since
> still some missing code changes for cluster idle states are missing.
> like clock PWR_CTR and PWR_CTRL2.

I cannot judge now. All I can test now is a that the boards enters those
idle states and system works stable. I cannot measure power consumption,
because currently I have only remote access to the boards.

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland