Re: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency invariance
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: 2021-06-22 06:53:06
Also in:
linux-acpi, lkml
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