Messages in this thread | | | Date | Tue, 22 Jun 2021 12:22:59 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency invariance |
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On 21-06-21, 16:48, Qian Cai wrote: > Viresh, this series works fine on my quick tests so far.
Thanks for testing.
> BTW, I > noticed some strange things even with the series applied mentioned > below when reading acpi_cppc vs cpufreq sysfs. Do you happen to know > are those just hardware/firmware issues because Linux just > faithfully exported the register values?
The values are exported by drivers/acpi/cppc_acpi.c I believe and they look to be based on simple register reads.
> == Arm64 server Foo == > CPU max MHz: 3000.0000 > CPU min MHz: 1000.0000 > > /sys/devices/system/cpu/cpu0/acpi_cppc/highest_perf > 300 > /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_freq > 1000 > /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_nonlinear_perf > 200 > /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_perf > 100 > /sys/devices/system/cpu/cpu0/acpi_cppc/nominal_freq <--- should be 3000? > 2800 > /sys/devices/system/cpu/cpu0/acpi_cppc/nominal_perf <--- should be 300? > 280
nominal-perf is max perf, and highest-perf is boost-perf. Same goes with nominal-freq (i.e. policy->max).
So 280 and 2800 look to be the correct values, 300 and 3000 come with boost enabled. Look at the first entry, highest_perf.
> /sys/devices/system/cpu/cpu0/acpi_cppc/reference_perf > 100 > > == Arm64 server Bar == > CPU max MHz: 3000.0000 > CPU min MHz: 375.0000 > > /sys/devices/system/cpu/cpu0/acpi_cppc/highest_perf <--- should be 3000? There is no cpufreq boost. > 3300
This isn't exported by cpufreq driver but acpi, and it just exports hardware values of highest_perf (with boost i.e.). cpufreq may or may not use this to support boost.
> /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_freq <--- don't understand why 0. > 0
Because corresponding hardware registers aren't implemented for your platform, this is the function that reads these registers:
int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps) { ...
/* Read optional lowest and nominal frequencies if present */ if (CPC_SUPPORTED(low_freq_reg)) cpc_read(cpunum, low_freq_reg, &low_f);
if (CPC_SUPPORTED(nom_freq_reg)) cpc_read(cpunum, nom_freq_reg, &nom_f);
perf_caps->lowest_freq = low_f; perf_caps->nominal_freq = nom_f; }
> /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_nonlinear_perf > 375 > /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_perf > 375 > /sys/devices/system/cpu/cpu0/acpi_cppc/nominal_freq <--- ditto > 0 > /sys/devices/system/cpu/cpu0/acpi_cppc/nominal_perf > 3000 > /sys/devices/system/cpu/cpu0/acpi_cppc/reference_perf > 100
-- viresh
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