On 26/10/2018 06:11, Viresh Kumar wrote: > On 25-10-18, 14:04, Daniel Lezcano wrote: >> I think it is actually correct. The example is confusing on what the >> numbers are. IIUC, it is: >> >> (after normalizing) >> >> dhrystone result on big CPU is 1024 at 1100MHz >> dhrystone result on little CPU is 446 at 850MHz >> >> We have to scale the result of the little for 1100MHz in order to compare. >> >> 1100/850 = 1.294 >> >> dhrystone result on little CPU is 446 * 1.294 = 577 at 1100MHz >> >> So we put the normalized values 1024 and 577. The arch_topology will >> scale 577 back to 446 as it will compute the max capacity based on the >> max freq which is 850MHz. >> >> The *final* capacities are 1024 for cluster0 and 446 for cluster1 (read >> the cpu max capacity, the ones showed in the sysfs). >> >> Did I miss something ? > > No. What about making it more clear in the example to save the next idiot (like > me) from wasting time :) > > diff --git a/Documentation/devicetree/bindings/arm/cpu-capacity.txt b/Documentation/devicetree/bindings/arm/cpu-capacity.txt > index 9b5685a1d15d..d061e6575bde 100644 > --- a/Documentation/devicetree/bindings/arm/cpu-capacity.txt > +++ b/Documentation/devicetree/bindings/arm/cpu-capacity.txt > @@ -61,7 +61,10 @@ mhz values (normalized w.r.t. the highest value found while parsing the DT). > Example 1 (ARM 64-bit, 6-cpu system, two clusters): > capacities-dmips-mhz are scaled w.r.t. 1024 (cpu@0 and cpu@1) > supposing cluster0@max-freq=1100 and custer1@max-freq=850, > -final capacities are 1024 for cluster0 and 446 for cluster1 > +final capacities are 1024 for cluster0 and 446 for cluster1. > +Note that the values mentioned below in the example (1024 and 578) > +aren't normalized based on max frequency of each cluster and that is > +left for the operating system to do. Yes, it will help but if you want to make things even more clear, I suggest to elaborate the text a bit and give the numbers above to explain (1100/850=1.294, 446 * 1.294 = 577, ...) -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
