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[v2,0/2] AMD Pstate driver fixes

Message ID 20240702081413.5688-1-Dhananjay.Ugwekar@amd.com
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Series AMD Pstate driver fixes | expand

Message

Dhananjay Ugwekar July 2, 2024, 8:14 a.m. UTC 
1. Handle the nominal freq units inconsistency in amd-pstate-ut, which was
leading to the below error on inserting the amd-pstate-ut module.

[ 4982.498864] amd_pstate_ut: 1    amd_pstate_ut_acpi_cpc_valid  success!
[ 4982.498873] amd_pstate_ut: 2    amd_pstate_ut_check_enabled   success!
[ 4982.509151] amd_pstate_ut: 3    amd_pstate_ut_check_perf      success!
[ 4982.509155] amd_pstate_ut: amd_pstate_ut_check_freq cpu0 max=3709000  >= nominal=2401 > lowest_nonlinear=1903000 > min=400000 > 0, the formula is incorrect!
[ 4982.509157] amd_pstate_ut: 4    amd_pstate_ut_check_freq      fail!

2. Setting the scaling_max_freq on shared memory CPPC systems was
broken in amd-pstate-epp driver(amd_pstate=active mode). The
scaling_max_freq value was not being propagated to the shared memory area, 
so the frequency capping was not being honored.

Tested on a AMD Zen3 Milan machine(shared memory CPPC): 

stress-ng is running on the system to keep the CPU utilization at 100%
to test the scaling_max_freq capping.

Before the patch:
We can see below, setting the scaling_max_freq is not taking effect.
 
linux/tools/power/x86/turbostat# ./turbostat --Summary
turbostat version 2023.11.07 - Len Brown <lenb@kernel.org>
[Snip]
cpu0: cpufreq driver: amd-pstate-epp
cpu0: cpufreq governor: performance
[Snip]
Avg_MHz Busy%   Bzy_MHz TSC_MHz IPC     IRQ     POLL    C1      C2      POLL%   C1%     C2%     CorWatt PkgWatt
2620    100.00  2620    2026    0.80    164935  0       0       0       0.00    0.00    0.00    176.07  249.18
2580    100.00  2580    1995    0.80    162208  0       0       0       0.00    0.00    0.00    173.27  245.37
2584    100.00  2584    1998    0.79    162379  0       0       0       0.00    0.00    0.00    173.42  245.68
2577    100.00  2577    1996    0.79    162146  0       0       0       0.00    0.00    0.00    173.15  245.41
2578    100.00  2578    1996    0.80    162025  0       0       0       0.00    0.00    0.00    173.07  245.46
2575    100.00  2575    1996    0.80    162115  0       0       0       0.00    0.00    0.00    172.96  245.41
2576    100.00  2576    1996    0.79    161998  0       0       0       0.00    0.00    0.00    172.87  245.32
linux/tools/power/x86/turbostat# echo 2000000 | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq
2000000
linux/tools/power/x86/turbostat# cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq | uniq
2000000
linux/tools/power/x86/turbostat# ./turbostat --Summary
turbostat version 2023.11.07 - Len Brown <lenb@kernel.org>
[Snip]
cpu0: cpufreq driver: amd-pstate-epp
cpu0: cpufreq governor: performance
[Snip]
Avg_MHz Busy%   Bzy_MHz TSC_MHz IPC     IRQ     POLL    C1      C2      POLL%   C1%     C2%     CorWatt PkgWatt
2620    100.00  2620    2038    0.79    166103  0       0       2       0.00    0.00    0.00    175.44  250.96
2566    100.00  2566    1996    0.79    162038  0       0       0       0.00    0.00    0.00    171.79  245.23
2566    100.00  2566    1996    0.79    162289  0       0       0       0.00    0.00    0.00    171.76  245.59
2571    100.00  2571    1996    0.80    162034  0       0       0       0.00    0.00    0.00    171.69  245.44
2566    100.00  2566    1996    0.79    162179  0       0       0       0.00    0.00    0.00    171.62  245.41
2567    100.00  2567    1996    0.79    162028  0       0       0       0.00    0.00    0.00    171.57  245.46
2567    100.00  2567    1996    0.80    162037  0       0       0       0.00    0.00    0.00    171.53  245.41

After applying the patch:
On setting scaling_max_freq at 2GHz, the CPU frequency gets capped at 2GHz.

linux/tools/power/x86/turbostat# ./turbostat --Summary
turbostat version 2023.11.07 - Len Brown <lenb@kernel.org>
[Snip]
cpu0: cpufreq driver: amd-pstate-epp
cpu0: cpufreq governor: performance
[Snip]
Avg_MHz Busy%   Bzy_MHz TSC_MHz IPC     IRQ     POLL    C1      C2      POLL%   C1%     C2%     CorWatt PkgWatt
2551    100.00  2551    1956    0.80    165998  0       0       0       0.00    0.00    0.00    171.34  231.22
2713    100.00  2713    2078    0.79    175801  0       0       0       0.00    0.00    0.00    181.92  266.13
2594    100.00  2594    1991    0.79    162183  0       0       1       0.00    0.00    0.00    173.99  244.50
2606    100.00  2606    2003    0.79    162632  0       0       0       0.00    0.00    0.00    174.81  246.51
2599    100.00  2599    1996    0.79    162168  0       0       0       0.00    0.00    0.00    174.05  245.46
linux/tools/power/x86/turbostat# echo 2000000 | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq
2000000
linux/tools/power/x86/turbostat# cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq | uniq
2000000
linux/tools/power/x86/turbostat# ./turbostat --Summary
turbostat version 2023.11.07 - Len Brown <lenb@kernel.org>
[Snip]
cpu0: cpufreq driver: amd-pstate-epp
cpu0: cpufreq governor: performance
[Snip]
Avg_MHz Busy%   Bzy_MHz TSC_MHz IPC     IRQ     POLL    C1      C2      POLL%   C1%     C2%     CorWatt PkgWatt
2010    100.00  2010    2030    0.80    165565  0       0       0       0.00    0.00    0.00    101.22  173.52
1975    100.00  1975    1995    0.80    162042  0       0       0       0.00    0.00    0.00    99.03   169.88
1977    100.00  1977    1998    0.80    162559  0       0       0       0.00    0.00    0.00    99.16   170.20
1976    100.00  1976    1996    0.80    162243  0       0       0       0.00    0.00    0.00    99.09   170.08
1976    100.00  1976    1996    0.80    162490  0       0       0       0.00    0.00    0.00    99.17   170.16
1976    100.00  1976    1996    0.80    162056  0       0       0       0.00    0.00    0.00    99.11   170.17

Dhananjay Ugwekar (2):
  cpufreq/amd-pstate-ut: Convert nominal_freq to khz during comparisons
  cpufreq/amd-pstate: Fix the scaling_max_freq setting on shared memory
    CPPC systems

 drivers/cpufreq/amd-pstate-ut.c | 12 +++++----
 drivers/cpufreq/amd-pstate.c    | 43 ++++++++++++++++++---------------
 2 files changed, 30 insertions(+), 25 deletions(-)