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

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Date: Sat, 10 Feb 2024 00:28:06 +0300
From: Dmitry Rokosov <ddrokosov@...utedevices.com>
To: <neil.armstrong@...aro.org>, <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>, Dmitry Rokosov
	<ddrokosov@...utedevices.com>
Subject: [PATCH v1 2/2] arm64: dts: amlogic: axg: initialize default SoC capacitance

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>;
 		};
 
-- 
2.43.0