linux-kernel - Re: [PATCH v2 2/4] arm64: dts: allwinner: h6: Add cooling map for GPU

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Message-ID: <a45abb3d-b765-c87b-df2c-85a03b5634cd@sholland.org>
Date:   Sat, 3 Sep 2022 22:24:38 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Clément Péron <peron.clem@...il.com>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-sunxi@...ts.linux.dev,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] arm64: dts: allwinner: h6: Add cooling map for GPU

On 8/27/22 11:49 AM, Clément Péron wrote:
> Hi Samuel,
> 
> On Tue, 23 Aug 2022 at 05:16, Samuel Holland <samuel@...lland.org> wrote:
>>
>> On 8/21/22 12:30 PM, Clément Péron wrote:
>>> Add a simple cooling map for the GPU.
>>
>> It would be good to document where the trip point temperatures came from.
> 
> If I remember correctly, I got those when getting the dtb from my
> Beelink GS1 when it was running vendor Android with the oldest
> Allwinner kernel.
> 
> But now that you ask I double check with the "new" vendor kernel source:
> https://github.com/Allwinner-Homlet/H6-BSP4.9-linux/blob/master/arch/arm64/boot/dts/sunxi/sun50iw6p1.dtsi#L2034-L2053
> 
> And It's different from what I got in the past.
> The throttling starts when the GPU is already very hot (95, 100 and
> 105°C) and seems to only disable the highest frequency (756, 624 and
> 576MHz).
> Which let the GPU running at 0.91V @ 540MHz.
> 
> Which is far to be the lowest possible consumption for the GPU (0.81V
> @ 336MHz would be better in the hottest situation)
> 
> I'm not an expert but either I could just try to copy/paste the same
> behavior or try to have a more smooth cooling map (70, 85, 100°C).
> 
> What do you think?

I would generally prefer something conservative, to be appropriate for most
boards. But I do not have any strong opinion on the exact trip points used; I am
fine with adjusting them.

Mostly I want to know the source of the cooling map -- where the numbers came
from, and what changes were made. That provides context if we want to change the
map in the future, or if we run in to issues on some other board.

Regards,
Samuel