linux-kernel - [PATCH 6/7] arm64: dts: juno: Add cpu dynamic-power-coefficient information

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Date:   Mon, 28 Jan 2019 16:55:21 +0000
From:   Quentin Perret <quentin.perret@....com>
To:     rjw@...ysocki.net, viresh.kumar@...aro.org, sudeep.holla@....com,
        liviu.dudau@....com, lorenzo.pieralisi@....com, robh+dt@...nel.org,
        mark.rutland@....com, nm@...com, sboyd@...nel.org
Cc:     linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        dietmar.eggemann@....com, mka@...omium.org, quentin.perret@....com
Subject: [PATCH 6/7] arm64: dts: juno: Add cpu dynamic-power-coefficient information

From: Dietmar Eggemann <dietmar.eggemann@....com>

A CPUfreq driver, like the scpi driver used on Juno boards, which
provide the Energy Model with power cost information via the PM_OPP
of_dev_pm_opp_get_cpu_power() function, do need the
dynamic-power-coefficient (C) in the device tree.

Method used to obtain the C value:
C is computed by measuring energy (E) consumption of a frequency domain
(FD) over a 10s runtime (t) sysbench workload running at each Operating
Performance Point (OPP) affine to 1 or 2 CPUs of that FD while the other
CPUs of the system are hotplugged out.
By definition all CPUs of a FD have the the same micro-architecture. An
OPP is characterized by a certain frequency (f) and voltage (V) value.
The corresponding power values (P) are calculated by dividing the delta
of the E values between the runs with 2 and 1 CPUs by t.

With n data tuples (P, f, V), n equal to number of OPPs for this
frequency domain, we can solve C by:

P = Pstat + Pdyn

P = Pstat + CV²f

Cx = (Px - P1)/(Vx²fx - V1²f1) with x = {2, ..., n}

The C value is the arithmetic mean out of {C2, ..., Cn}.

Since DVFS is broken on Juno r1, no dynamic-power-coefficient
information has been added to its dts file.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
Signed-off-by: Quentin Perret <quentin.perret@....com>
---
 arch/arm64/boot/dts/arm/juno-r2.dts | 6 ++++++
 arch/arm64/boot/dts/arm/juno.dts    | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/arm64/boot/dts/arm/juno-r2.dts b/arch/arm64/boot/dts/arm/juno-r2.dts
index ab77adb4f3c2..66f0ec79c864 100644
--- a/arch/arm64/boot/dts/arm/juno-r2.dts
+++ b/arch/arm64/boot/dts/arm/juno-r2.dts
@@ -99,6 +99,7 @@
 			clocks = <&scpi_dvfs 0>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <1024>;
+			dynamic-power-coefficient = <450>;
 		};
 
 		A72_1: cpu@1 {
@@ -116,6 +117,7 @@
 			clocks = <&scpi_dvfs 0>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <1024>;
+			dynamic-power-coefficient = <450>;
 		};
 
 		A53_0: cpu@100 {
@@ -133,6 +135,7 @@
 			clocks = <&scpi_dvfs 1>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <485>;
+			dynamic-power-coefficient = <140>;
 		};
 
 		A53_1: cpu@101 {
@@ -150,6 +153,7 @@
 			clocks = <&scpi_dvfs 1>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <485>;
+			dynamic-power-coefficient = <140>;
 		};
 
 		A53_2: cpu@102 {
@@ -167,6 +171,7 @@
 			clocks = <&scpi_dvfs 1>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <485>;
+			dynamic-power-coefficient = <140>;
 		};
 
 		A53_3: cpu@103 {
@@ -184,6 +189,7 @@
 			clocks = <&scpi_dvfs 1>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <485>;
+			dynamic-power-coefficient = <140>;
 		};
 
 		A72_L2: l2-cache0 {
diff --git a/arch/arm64/boot/dts/arm/juno.dts b/arch/arm64/boot/dts/arm/juno.dts
index 08d4ba1716c3..9890afdda77b 100644
--- a/arch/arm64/boot/dts/arm/juno.dts
+++ b/arch/arm64/boot/dts/arm/juno.dts
@@ -98,6 +98,7 @@
 			clocks = <&scpi_dvfs 0>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <1024>;
+			dynamic-power-coefficient = <530>;
 		};
 
 		A57_1: cpu@1 {
@@ -115,6 +116,7 @@
 			clocks = <&scpi_dvfs 0>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <1024>;
+			dynamic-power-coefficient = <530>;
 		};
 
 		A53_0: cpu@100 {
@@ -132,6 +134,7 @@
 			clocks = <&scpi_dvfs 1>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <578>;
+			dynamic-power-coefficient = <140>;
 		};
 
 		A53_1: cpu@101 {
@@ -149,6 +152,7 @@
 			clocks = <&scpi_dvfs 1>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <578>;
+			dynamic-power-coefficient = <140>;
 		};
 
 		A53_2: cpu@102 {
@@ -166,6 +170,7 @@
 			clocks = <&scpi_dvfs 1>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <578>;
+			dynamic-power-coefficient = <140>;
 		};
 
 		A53_3: cpu@103 {
@@ -183,6 +188,7 @@
 			clocks = <&scpi_dvfs 1>;
 			cpu-idle-states = <&CPU_SLEEP_0 &CLUSTER_SLEEP_0>;
 			capacity-dmips-mhz = <578>;
+			dynamic-power-coefficient = <140>;
 		};
 
 		A57_L2: l2-cache0 {
-- 
2.20.1