[Bug 219110] amd-pstate's balance_performance energy_performance_preference doesn't survive suspend resume

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=219110

--- Comment #8 from Mario Limonciello (AMD) (mario.limonciello@amd.com) ---
To me this sounds like a firmware bug.  I can't seem to reproduce it.

I just had a try on an AMD reference system with a "AMD Ryzen 5 7640U w/ Radeon
760M Graphics" running PhoenixPI-FP8-FP7 1.1.0.2a.

For my kernel I used 6.11-rc4.
For userspace it's Ubuntu 24.04 userspace.
I ran "mpv bbb_sunflower_2160p_60fps_normal.mp4".

I then SSH'ed in from another system and looked at the average PPT value
reported by 'sensors'.  It stay in the 8W range the whole time.  Here was a
snapshot:

amdgpu-pci-c200
Adapter: PCI adapter
vddgfx:      900.00 mV
vddnb:       759.00 mV
edge:         +39.0°C
PPT:           6.00 W  (avg =   8.14 W)

I then stopped the video, suspended and started it back up and looked again. 
Same ballpark.

You might look at the value for the MSR's that amd-pstate uses by using 'rdmsr
MSR' to see if they change in any notable way before or after suspend.

#define MSR_AMD_CPPC_CAP1               0xc00102b0
#define MSR_AMD_CPPC_ENABLE             0xc00102b1
#define MSR_AMD_CPPC_CAP2               0xc00102b2
#define MSR_AMD_CPPC_REQ                0xc00102b3
#define MSR_AMD_CPPC_STATUS             0xc00102b4

The most important one to check is MSR_AMD_CPPC_REQ.

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