Re: [PATCH] arm64: dts: hisilicon: Add hi3660 cpu capacity-dmips-mhz information

[Valentin Schneider <valentin.schneider@xxxxxxx>]

Hi Leo,


On 12/13/2017 02:53 PM, Leo Yan wrote:
> Hi Valentin,
>
> On Wed, Dec 13, 2017 at 02:21:06PM +0000, Valentin Schneider wrote:
> > The following dt entries are added:
> >   cpus [0-3] (Cortex A53):
> >     - capacity-dmips-mhz = <592>;
> >
> >   cpus [4-7] (Cortex A73):
> >     - capacity-dmips-mhz = <1024>;
> >
> > Those values were obtained by running dhrystone 2.1 on a
> > HiKey960 with the following procedure:
> > - Offline all CPUs but CPU0 (A53)
> > - Set CPU0 frequency to maximum
> > - Run Dhrystone 2.1 for 20 seconds
> >
> > - Offline all CPUs but CPU4 (A73)
> > - set CPU4 frequency to maximum
> > - Run Dhrystone 2.1 for 20 seconds
> >
> > The results are as follows:
> > A53: 129633887 loops
> > A73: 287034147 loops
> Seems to me the capacity-dmips-mhz should be:
>
> CA53: 129633887 / 20 / 1844 = 3515
> CA73: 287034147 / 20 / 2362 = 6076
>
> After normalized to range [0..1024], we could get:
>
> CA53:  592
> CA73: 1024

Yes, that's the "direct approach". I wanted to underline the fact that 
there are two different max frequencies so what I followed would be:

1) Computing the performance ratio:
(129633887 / 287034147) * 1024 = 462.47

2) Scaling that to the same frequency scale:
462.47 * (2362/1844) = 592.38

Which gives the same end result (it's the same equation but split in two 
steps). Also it makes it easy to check that the cpu_capacity sysfs entry 
for the A53s gets correctly set (to 462).

> Reviewed-by: Leo Yan <leo.yan@xxxxxxxxxx>
>
> > By scaling those values so that the A73s use 1024, we end up with 462
> > for the A53s. However, they have different maximum frequencies:
> > 1.844GHz for A53s and 2.362GHz for A73s. Thus, we can scale the A53
> > value to truly represent dmips per MHz, and we end up with 592.
> >
> > The impact of this change can be verified on HiKey960:
> >
> > $ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq
> > 1844000
> > 1844000
> > 1844000
> > 1844000
> > 2362000
> > 2362000
> > 2362000
> > 2362000
> >
> > $ cat /sys/devices/system/cpu/cpu*/cpu_capacity
> > 462
> > 462
> > 462
> > 462
> > 1024
> > 1024
> > 1024
> > 1024
> >
> > Signed-off-by: Valentin Schneider <valentin.schneider@xxxxxxx>
> > ---
> >   arch/arm64/boot/dts/hisilicon/hi3660.dtsi | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/hisilicon/hi3660.dtsi b/arch/arm64/boot/dts/hisilicon/hi3660.dtsi
> > index ab0b95b..04a8d28 100644
> > --- a/arch/arm64/boot/dts/hisilicon/hi3660.dtsi
> > +++ b/arch/arm64/boot/dts/hisilicon/hi3660.dtsi
> > @@ -61,6 +61,7 @@
> >   			enable-method = "psci";
> >   			next-level-cache = <&A53_L2>;
> >   			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP_0>;
> > +			capacity-dmips-mhz = <592>;
> >   		};
> >   
> >   		cpu1: cpu@1 {
> > @@ -70,6 +71,7 @@
> >   			enable-method = "psci";
> >   			next-level-cache = <&A53_L2>;
> >   			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP_0>;
> > +			capacity-dmips-mhz = <592>;
> >   		};
> >   
> >   		cpu2: cpu@2 {
> > @@ -79,6 +81,7 @@
> >   			enable-method = "psci";
> >   			next-level-cache = <&A53_L2>;
> >   			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP_0>;
> > +			capacity-dmips-mhz = <592>;
> >   		};
> >   
> >   		cpu3: cpu@3 {
> > @@ -88,6 +91,7 @@
> >   			enable-method = "psci";
> >   			next-level-cache = <&A53_L2>;
> >   			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP_0>;
> > +			capacity-dmips-mhz = <592>;
> >   		};
> >   
> >   		cpu4: cpu@100 {
> > @@ -101,6 +105,7 @@
> >   					&CPU_SLEEP
> >   					&CLUSTER_SLEEP_1
> >   			>;
> > +			capacity-dmips-mhz = <1024>;
> >   		};
> >   
> >   		cpu5: cpu@101 {
> > @@ -114,6 +119,7 @@
> >   					&CPU_SLEEP
> >   					&CLUSTER_SLEEP_1
> >   			>;
> > +			capacity-dmips-mhz = <1024>;
> >   		};
> >   
> >   		cpu6: cpu@102 {
> > @@ -127,6 +133,7 @@
> >   					&CPU_SLEEP
> >   					&CLUSTER_SLEEP_1
> >   			>;
> > +			capacity-dmips-mhz = <1024>;
> >   		};
> >   
> >   		cpu7: cpu@103 {
> > @@ -140,6 +147,7 @@
> >   					&CPU_SLEEP
> >   					&CLUSTER_SLEEP_1
> >   			>;
> > +			capacity-dmips-mhz = <1024>;
> >   		};
> >   
> >   		idle-states {
> > --
> > 2.7.4

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