linux-kernel - [PATCH] arm64: dts: meson: Add capacity-dmips-mhz attributes to GXM

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Date:   Tue, 24 Nov 2020 12:17:40 +0000
From:   Christian Hewitt <christianshewitt@...il.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Kevin Hilman <khilman@...libre.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Christian Hewitt <christianshewitt@...il.com>
Subject: [PATCH] arm64: dts: meson: Add capacity-dmips-mhz attributes to GXM

GXM (S912) is a big-little design with CPUs 0-3 clocked at 1.5GHz
and CPUs 4-7 at 1.0GHz. Adding capacity-dmips-mhz attributes allows
the scheduler to factor the different clock speeds into capacity
calculations and prefer the higher-clocked cluster to improve
overall performance.

This was inspired by the similar change for G12B [0] boards. The
diference here is that all cores are A53's so the same dmips-mhz
value is used.

VIM2:~ # cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq
1512000
1512000
1512000
1512000
1000000
1000000
1000000
1000000

before:

VIM2:~ # cat /sys/devices/system/cpu/cpu*/cpu_capacity
1024
1024
1024
1024
1024
1024
1024
1024

after:

VIM2:~ # cat /sys/devices/system/cpu/cpu*/cpu_capacity
1024
1024
1024
1024
677
677
677
677

The after value matches my table-napkin calculation:

(1000000 / 1512000 = 0.661) * 1024 = 677

[0] https://github.com/torvalds/linux/commit/6eeaf4d2452ec8b1ece58776812140734fc2e088

Signed-off-by: Christian Hewitt <christianshewitt@...il.com>
---
 arch/arm64/boot/dts/amlogic/meson-gxm.dtsi | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/arm64/boot/dts/amlogic/meson-gxm.dtsi b/arch/arm64/boot/dts/amlogic/meson-gxm.dtsi
index fe4145112295..411cc312fc62 100644
--- a/arch/arm64/boot/dts/amlogic/meson-gxm.dtsi
+++ b/arch/arm64/boot/dts/amlogic/meson-gxm.dtsi
@@ -42,11 +42,28 @@
 			};
 		};
 
+		cpu0: cpu@0 {
+			capacity-dmips-mhz = <1024>;
+		};
+
+		cpu1: cpu@1 {
+			capacity-dmips-mhz = <1024>;
+		};
+
+		cpu2: cpu@2 {
+			capacity-dmips-mhz = <1024>;
+		};
+
+		cpu3: cpu@3 {
+			capacity-dmips-mhz = <1024>;
+		};
+
 		cpu4: cpu@100 {
 			device_type = "cpu";
 			compatible = "arm,cortex-a53";
 			reg = <0x0 0x100>;
 			enable-method = "psci";
+			capacity-dmips-mhz = <1024>;
 			next-level-cache = <&l2>;
 			clocks = <&scpi_dvfs 1>;
 			#cooling-cells = <2>;
@@ -57,6 +74,7 @@
 			compatible = "arm,cortex-a53";
 			reg = <0x0 0x101>;
 			enable-method = "psci";
+			capacity-dmips-mhz = <1024>;
 			next-level-cache = <&l2>;
 			clocks = <&scpi_dvfs 1>;
 			#cooling-cells = <2>;
@@ -67,6 +85,7 @@
 			compatible = "arm,cortex-a53";
 			reg = <0x0 0x102>;
 			enable-method = "psci";
+			capacity-dmips-mhz = <1024>;
 			next-level-cache = <&l2>;
 			clocks = <&scpi_dvfs 1>;
 			#cooling-cells = <2>;
@@ -77,6 +96,7 @@
 			compatible = "arm,cortex-a53";
 			reg = <0x0 0x103>;
 			enable-method = "psci";
+			capacity-dmips-mhz = <1024>;
 			next-level-cache = <&l2>;
 			clocks = <&scpi_dvfs 1>;
 			#cooling-cells = <2>;
-- 
2.17.1