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Message-ID: <cf835a26-1a76-4cf4-840a-c0bc6cb03452@amd.com>
Date: Tue, 2 Jul 2024 13:54:50 +0530
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: rafael@...nel.org, viresh.kumar@...aro.org, gautham.shenoy@....com,
 mario.limonciello@....com, perry.yuan@....com, skhan@...uxfoundation.org,
 li.meng@....com, ray.huang@....com
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] AMD Pstate driver fixes

Forgot to mention the v2 changes,

v2 changes:
* Add reported-by tags (Gautham)
* Modify patch 2 to use amd_pstate_update_perf (Mario) 
* Modify commit name for patch 1 (Gautham)
* Modify commit message for patch 2, from scaling_min/max_freq to 
  just scaling_max_freq, as scaling_min_freq still needs some debugging
  to work correctly with active mode.

Regards,
Dhananjay

On 7/2/2024 1:44 PM, Dhananjay Ugwekar wrote:
> 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@...nel.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@...nel.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@...nel.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@...nel.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(-)
> 

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