linux-kernel - Re: [PATCH v1 2/2] arm64: dts: amlogic: axg: initialize default SoC capacitance

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Message-ID: <34ee9676-567f-4c07-83b0-f3b8b1e08db9@linaro.org>
Date: Mon, 12 Feb 2024 16:02:49 +0100
From: neil.armstrong@...aro.org
To: Dmitry Rokosov <ddrokosov@...utedevices.com>, jbrunet@...libre.com,
 mturquette@...libre.com, adeep@...ina.in, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, khilman@...libre.com,
 martin.blumenstingl@...glemail.com, conor+dt@...nel.org
Cc: kernel@...rdevices.ru, sdfw_system_team@...rdevices.ru,
 rockosov@...il.com, linux-amlogic@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 2/2] arm64: dts: amlogic: axg: initialize default SoC
 capacitance

On 09/02/2024 22:28, Dmitry Rokosov wrote:
> The capacitance value is required for the usage of the cpufreq cooling
> device and power_allocator thermal governor in the appropriate energy
> model.
> 
> It helps to compute the power estimated by the SoC at the appropriate
> frequency. If it is the frequency of an existing OPP, or at the
> frequency of the first OPP above the requested value otherwise.
> 
> The power is estimated as P = C * V^2 * f, with C being the SoC's
> capacitance and V and f respectively representing the voltage and
> frequency of the OPP.
> 
> Since AXG SoC doesn't have SCMI protocol support, we need to initialize
> capacitance using the 'dynamic-power-coefficient' DT entry. Its value is
> retrieved from the vendor kernel, and it gives us the following
> freq2power mapping:
>      +-----------+--------+
>      | frequency,| power, |
>      |    MHz    |   uW   |
>      +-----------+--------+
>      |     100   |  10354 |
>      +-----------+--------+
>      |     250   |  27104 |
>      +-----------+--------+
>      |     500   |  55447 |
>      +-----------+--------+
>      |     667   |  77327 |
>      +-----------+--------+
>      |    1000   | 129024 |
>      +-----------+--------+
>      |    1200   | 164656 |
>      +-----------+--------+
>      |    1296   | 192489 |
>      +-----------+--------+
>      |    1416   | 239870 |
>      +-----------+--------+
> 
> Signed-off-by: Dmitry Rokosov <ddrokosov@...utedevices.com>
> ---
>   arch/arm64/boot/dts/amlogic/meson-axg.dtsi | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/amlogic/meson-axg.dtsi b/arch/arm64/boot/dts/amlogic/meson-axg.dtsi
> index ea96fef328e8..6d12b760b90f 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-axg.dtsi
> +++ b/arch/arm64/boot/dts/amlogic/meson-axg.dtsi
> @@ -74,6 +74,7 @@ cpu0: cpu@0 {
>   			enable-method = "psci";
>   			next-level-cache = <&l2>;
>   			clocks = <&scpi_dvfs 0>;
> +			dynamic-power-coefficient = <140>;
>   			#cooling-cells = <2>;
>   		};
>   
> @@ -84,6 +85,7 @@ cpu1: cpu@1 {
>   			enable-method = "psci";
>   			next-level-cache = <&l2>;
>   			clocks = <&scpi_dvfs 0>;
> +			dynamic-power-coefficient = <140>;
>   			#cooling-cells = <2>;
>   		};
>   
> @@ -94,6 +96,7 @@ cpu2: cpu@2 {
>   			enable-method = "psci";
>   			next-level-cache = <&l2>;
>   			clocks = <&scpi_dvfs 0>;
> +			dynamic-power-coefficient = <140>;
>   			#cooling-cells = <2>;
>   		};
>   
> @@ -104,6 +107,7 @@ cpu3: cpu@3 {
>   			enable-method = "psci";
>   			next-level-cache = <&l2>;
>   			clocks = <&scpi_dvfs 0>;
> +			dynamic-power-coefficient = <140>;
>   			#cooling-cells = <2>;
>   		};
>   

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>