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

From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Anand Moon <linux.amoon@gmail.com>
Cc: Linux PM list <linux-pm@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	linux-samsung-soc@vger.kernel.org,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Lukasz Luba <lukasz.luba@arm.com>
Subject: Re: [PATCH 0/4] Restore big.LITTLE cpuidle driver for Exynos
Date: Wed, 17 Jun 2020 11:48:37 +0200	[thread overview]
Message-ID: <3e6b5dbb-a8a2-e3db-d740-53e13676455c@samsung.com> (raw)
In-Reply-To: <CANAwSgStsYP5fBB7z7-Reo2BP4ZQPT6RN4s8QdLGVGhKCDA_Ng@mail.gmail.com>

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