linux-6.6.y regression on amd-pstate

[Mario Limonciello]

+ stable
+ regressions
New subject

Great news.

Greg, Sasha,

Can you please pull in these 3 commits specifically to 6.6.y to fix a 
regression that was reported by Morgan in 6.6.y:

commit 12753d71e8c5 ("ACPI: CPPC: Add helper to get the highest 
performance value")
commit ed429c686b79 ("cpufreq: amd-pstate: Enable amd-pstate preferred 
core support")
commit 3d291fe47fe1 ("cpufreq: amd-pstate: fix the highest frequency 
issue which limits performance")

Further details are below.

Thanks!

On 9/5/2024 16:09, Jones, Morgan wrote:
> Mario,
>
> Confirmed. Thank you for the help! Slightly different refs on my end:
>
> Remotes:
>
> next    https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git (fetch)
> next    https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git (push)
> origin  git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git (fetch)
> origin  git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git (push)
> superm1 https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git/ (fetch)
> superm1 https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git/ (push)
> torvalds        git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git (fetch)
> torvalds        git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git (push)
>
> Patches:
>
> git format-patch 12753d71e8c5^..12753d71e8c5
> git format-patch f3a052391822b772b4e27f2594526cf1eb103cab^..f3a052391822b772b4e27f2594526cf1eb103cab
> git format-patch bf202e654bfa57fb8cf9d93d4c6855890b70b9c4^..bf202e654bfa57fb8cf9d93d4c6855890b70b9c4
>
> Results:
>
> Linux redact 6.6.48 #1-NixOS SMP PREEMPT_DYNAMIC Tue Jan  1 00:00:00 UTC 1980 x86_64 GNU/Linux
>
> analyzing CPU 56:
>    driver: amd-pstate-epp
>    CPUs which run at the same hardware frequency: 56
>    CPUs which need to have their frequency coordinated by software: 56
>    maximum transition latency:  Cannot determine or is not supported.
>    hardware limits: 400 MHz - 3.35 GHz
>    available cpufreq governors: performance powersave
>    current policy: frequency should be within 400 MHz and 3.35 GHz.
>                    The governor "performance" may decide which speed to use
>                    within this range.
>    current CPU frequency: Unable to call hardware
>    current CPU frequency: 2.09 GHz (asserted by call to kernel)
>    boost state support:
>      Supported: yes
>      Active: yes
>      AMD PSTATE Highest Performance: 255. Maximum Frequency: 3.35 GHz.
>      AMD PSTATE Nominal Performance: 152. Nominal Frequency: 2.00 GHz.
>      AMD PSTATE Lowest Non-linear Performance: 115. Lowest Non-linear Frequency: 1.51 GHz.
>      AMD PSTATE Lowest Performance: 31. Lowest Frequency: 400 MHz.
>
> And our builds are back to being fast with `amd_pstate=active amd_prefcore=enable amd_pstate.shared_mem=1`.
>
> Morgan
>
> -----Original Message-----
> From: Mario Limonciello <mario.limonciello@xxxxxxx>
> Sent: Thursday, September 5, 2024 8:12 AM
> To: Jones, Morgan <Morgan.Jones@xxxxxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; David Arcari <darcari@xxxxxxxxxx>; Dhananjay Ugwekar <Dhananjay.Ugwekar@xxxxxxx>; rafael@xxxxxxxxxx; viresh.kumar@xxxxxxxxxx; gautham.shenoy@xxxxxxx; perry.yuan@xxxxxxx; skhan@xxxxxxxxxxxxxxxxxxx; li.meng@xxxxxxx; ray.huang@xxxxxxx
> Subject: Re: [EXTERNAL] Re: [PATCH v2 2/2] cpufreq/amd-pstate: Fix the scaling_max_freq setting on shared memory CPPC systems
>
> Hi Morgan,
>
> Please apply these 3 commits:
>
> commit 12753d71e8c5 ("ACPI: CPPC: Add helper to get the highest performance value") commit ed429c686b79 ("cpufreq: amd-pstate: Enable amd-pstate preferred core support") commit 3d291fe47fe1 ("cpufreq: amd-pstate: fix the highest frequency issue which limits performance")
>
> The first two should help your system, the third will prevent introducing a regression on a different one.
>
> Assuming that works we should ask @stable to pull all 3 in to fix this regression.
>
> Thanks,
>
> On 9/4/2024 08:57, Mario Limonciello wrote:
> > Morgan,
> >
> > I was referring specfiically to the version that landed in Linus' tree:
> > https://urldefense.us/v3/__https://git.kernel.org/torvalds/c/8164f7433
> > 264__;!!C5Asm8uRnZQmlRln!aIZEDEbIUKD7OrxN0b0KjoqKYDL2yMkwk4EK7x_oSnyHQ
> > 6MEq7yt6JHjd0TD9DgEYEWDcF58OKL8c7G11bT3dSqL8eM$
> >
> > But yeah it's effectively the same thing.  In any case, it's not the
> > solution.
> >
> > We had some internal discussion and suspect this is due to missing
> > prefcore patches in 6.6 as that feature landed in 6.9.  We'll try to
> > reproduce this on a Rome system and come back with our findings and
> > suggestions what to do.
> >
> > Thanks,