From: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
A CPUfreq driver, like the ARM big.LITTLE driver used on the TC2 board,
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}.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Signed-off-by: Quentin Perret <quentin.perret@xxxxxxx>
---
arch/arm/boot/dts/vexpress-v2p-ca15_a7.dts | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/arm/boot/dts/vexpress-v2p-ca15_a7.dts b/arch/arm/boot/dts/vexpress-v2p-ca15_a7.dts
index a2ccacd07f4f..00cd9f5bef2e 100644
--- a/arch/arm/boot/dts/vexpress-v2p-ca15_a7.dts
+++ b/arch/arm/boot/dts/vexpress-v2p-ca15_a7.dts
@@ -42,6 +42,7 @@
cci-control-port = <&cci_control1>;
cpu-idle-states = <&CLUSTER_SLEEP_BIG>;
capacity-dmips-mhz = <1024>;
+ dynamic-power-coefficient = <990>;
};
cpu1: cpu@1 {
@@ -51,6 +52,7 @@
cci-control-port = <&cci_control1>;
cpu-idle-states = <&CLUSTER_SLEEP_BIG>;
capacity-dmips-mhz = <1024>;
+ dynamic-power-coefficient = <990>;
};
cpu2: cpu@2 {
@@ -60,6 +62,7 @@
cci-control-port = <&cci_control2>;
cpu-idle-states = <&CLUSTER_SLEEP_LITTLE>;
capacity-dmips-mhz = <516>;
+ dynamic-power-coefficient = <133>;
};
cpu3: cpu@3 {
@@ -69,6 +72,7 @@
cci-control-port = <&cci_control2>;
cpu-idle-states = <&CLUSTER_SLEEP_LITTLE>;
capacity-dmips-mhz = <516>;
+ dynamic-power-coefficient = <133>;
};
cpu4: cpu@4 {
@@ -78,6 +82,7 @@
cci-control-port = <&cci_control2>;
cpu-idle-states = <&CLUSTER_SLEEP_LITTLE>;
capacity-dmips-mhz = <516>;
+ dynamic-power-coefficient = <133>;
};
idle-states {
--
2.20.1
