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([2a01:e34:ed2f:f020:ddd7:1eb:a66:7a85]) by smtp.googlemail.com with ESMTPSA id l15sm6781389wme.43.2021.03.19.07.35.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 19 Mar 2021 07:35:14 -0700 (PDT) Subject: Re: [PATCH] dt: rockchip: rk3399: Add dynamic power coefficient for GPU To: Robin Murphy , heiko@sntech.de Cc: Rob Herring , Johan Jonker , Helen Koike , Shunqian Zheng , Jacob Chen , Chen-Yu Tsai , Markus Reichl , Boris Brezillon , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , "moderated list:ARM/Rockchip SoC support" , "open list:ARM/Rockchip SoC support" , open list References: <20210319110511.24787-1-daniel.lezcano@linaro.org> <5db868e4-5b86-7b32-51e0-665a2e1fc1ac@arm.com> From: Daniel Lezcano Message-ID: <9322db05-2cad-453c-ec1b-1fdb3df142fa@linaro.org> Date: Fri, 19 Mar 2021 15:35:13 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <5db868e4-5b86-7b32-51e0-665a2e1fc1ac@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Robin, On 19/03/2021 13:17, Robin Murphy wrote: > On 2021-03-19 11:05, Daniel Lezcano wrote: >> The DTPM framework is looking for upstream SoC candidates to share the >> power numbers. >> >> We can see around different numbers but the one which seems to be >> consistent with the initial post for the values on the CPUs can be >> found in the patch https://lore.kernel.org/patchwork/patch/810159/ > > The kernel hacker in me would be more inclined to trust the BSP that the > vendor actively supports than a 5-year-old patch that was never pursued > upstream. Apparently that was last updated more recently: > > https://github.com/rockchip-linux/kernel/commit/98d4505e1bd62ff028bd79fbd8284d64b6f468f8 Yes, I've seen this value also. > The ex-mathematician in me can't even comment either way without > evidence that whatever model expects to consume this value is even > comparable to whatever "arm,mali-simple-power-model" is. > > The way the > latter apparently needs an explicit "static" coefficient as well as a > "dynamic" one, and the value here being nearly 3 times that of a > similarly-named one in active use downstream (ChromeOS appears to still > be using the values from before the above commit), certainly incline me > to think they may not be... Sorry, I'm missing the point :/ We dropped in the kernel any static power computation because as there was no value, the resulting code was considered dead. So we rely on the dynamic power only. >> I don't know the precision of this value but it is better than >> nothing. > > But is it? If it leads to some throttling mechanism kicking in and > crippling GPU performance because it's massively overestimating power > consumption, that would be objectively worse for most users, no? No because there is no sustainable power specified for the thermal zones related to the GPU. -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog