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
