This is a note to let you know that I've just added the patch titled
arm64: dts: qcom: sdm845: correct dynamic power coefficients
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-dts-qcom-sdm845-correct-dynamic-power-coefficients.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 44750f153699b6e4f851a399287e5c8df208d696 Mon Sep 17 00:00:00 2001
From: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Date: Fri, 6 Jan 2023 17:46:18 +0100
Subject: arm64: dts: qcom: sdm845: correct dynamic power coefficients
From: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
commit 44750f153699b6e4f851a399287e5c8df208d696 upstream.
While stressing EAS on my dragonboard RB3, I have noticed that LITTLE cores
where never selected as the most energy efficient CPU whatever the
utilization level of waking task.
energy model framework uses its cost field to estimate the energy with
the formula:
nrg = cost of the selected OPP * utilization / CPU's max capacity
which ends up selecting the CPU with lowest cost / max capacity ration
as long as the utilization fits in the OPP's capacity.
If we compare the cost of a little OPP with similar capacity of a big OPP
like :
OPP(kHz) OPP capacity cost max capacity cost/max capacity
LITTLE 1766400 407 351114 407 863
big 1056000 408 520267 1024 508
This can be interpreted as the LITTLE core consumes 70% more than big core
for the same compute capacity.
According to [1], LITTLE consumes 10% less than big core for Coremark
benchmark at those OPPs. If we consider that everything else stays
unchanged, the dynamic-power-coefficient of LITTLE core should be
only 53% of the current value: 290 * 53% = 154
Set the dynamic-power-coefficient of CPU0-3 to 154 to fix the energy model.
[1] https://github.com/kdrag0n/freqbench/tree/master/results/sdm845/main
Fixes: 0e0a8e35d725 ("arm64: dts: qcom: sdm845: correct dynamic power coefficients")
Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Bjorn Andersson <andersson@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230106164618.1845281-1-vincent.guittot@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/boot/dts/qcom/sdm845.dtsi | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
+++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
@@ -197,7 +197,7 @@
&LITTLE_CPU_SLEEP_1
&CLUSTER_SLEEP_0>;
capacity-dmips-mhz = <611>;
- dynamic-power-coefficient = <290>;
+ dynamic-power-coefficient = <154>;
qcom,freq-domain = <&cpufreq_hw 0>;
operating-points-v2 = <&cpu0_opp_table>;
interconnects = <&gladiator_noc MASTER_APPSS_PROC 3 &mem_noc SLAVE_EBI1 3>,
@@ -222,7 +222,7 @@
&LITTLE_CPU_SLEEP_1
&CLUSTER_SLEEP_0>;
capacity-dmips-mhz = <611>;
- dynamic-power-coefficient = <290>;
+ dynamic-power-coefficient = <154>;
qcom,freq-domain = <&cpufreq_hw 0>;
operating-points-v2 = <&cpu0_opp_table>;
interconnects = <&gladiator_noc MASTER_APPSS_PROC 3 &mem_noc SLAVE_EBI1 3>,
@@ -244,7 +244,7 @@
&LITTLE_CPU_SLEEP_1
&CLUSTER_SLEEP_0>;
capacity-dmips-mhz = <611>;
- dynamic-power-coefficient = <290>;
+ dynamic-power-coefficient = <154>;
qcom,freq-domain = <&cpufreq_hw 0>;
operating-points-v2 = <&cpu0_opp_table>;
interconnects = <&gladiator_noc MASTER_APPSS_PROC 3 &mem_noc SLAVE_EBI1 3>,
@@ -266,7 +266,7 @@
&LITTLE_CPU_SLEEP_1
&CLUSTER_SLEEP_0>;
capacity-dmips-mhz = <611>;
- dynamic-power-coefficient = <290>;
+ dynamic-power-coefficient = <154>;
qcom,freq-domain = <&cpufreq_hw 0>;
operating-points-v2 = <&cpu0_opp_table>;
interconnects = <&gladiator_noc MASTER_APPSS_PROC 3 &mem_noc SLAVE_EBI1 3>,
Patches currently in stable-queue which might be from vincent.guittot@xxxxxxxxxx are
queue-5.15/arm64-dts-qcom-sdm845-correct-dynamic-power-coefficients.patch
