[Bug 206309] Experimental amdgpu w/ Dell E6540 with HD 8790M (MARS XTX), massive performance improvement after ACPI suspend

[bugzilla-daemon at kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=206309

--- Comment #5 from jerbear3.14159 at gmail.com ---
It's a Linux bug!

I finally set aside a day to waste on Windows installation to check whether it
behaves the same way. Windows 10 repeatedly crashed and bricked itself because
of course it did. It works perfectly on Windows 8.1 with the official graphics
driver on Dell's website.
https://dl.dell.com/FOLDER02868143M/5/AMD-FirePro-Graphics-Driver_CWRN6_WIN_14.502.1005_A02_02.EXE

Memory Clock (MHz)/Shader Clock (MHz):
Idle: 150/300
Battery: 600/400
AC: 1000/900

On Xubuntu 23.10 it's more like:
Idle: 150/300
Battery: 150/300
AC: 1000/900 (but it drops down to 150/300 after unplugging, and requires a
reboot to bring it back up)

I've gone through 2 official 130W Dell chargers and 2 90W Targus universal
chargers. Linux exhibits the power management bug regardless. I have never
tried a docking station.

uname -a gives:
Linux 6.5.0-44-generic #44-Ubuntu SMP PREEMPT_DYNAMIC Fri Jun  7 15:10:09 UTC
2024 x86_64 x86_64 x86_64 GNU/Linux

The only reprieve I've found is to follow these steps:
1. Boot with the laptop plugged in. If using a 90W charger and this is a cold
start (as opposed to a reboot), need to reboot as soon as it finishes booting.
2. echo -n high > /sys/class/drm/card1/device/power_dpm_force_performance_level
3. Pray
4. Unplug
5. Now for some reason, there's a small chance that the clock speeds stick high
and don't drop. If not, start over from step 1. If yes, then typically (but not
always) I can repeatedly unplug+plug safely up until it's time to shut down.

Problems I've encountered with this method include:
- Low success rate
- Runs hotter/harms battery life
- If I'm working unplugged, I need to manually lower the clock speeds down to
600/400. If I forget and leave it at 1000/900 and try to do anything
graphically intense, the battery can't provide enough power and the entire
laptop shuts down immediately. You can see that Windows does this automatically
when unplugged.

All in all, this is a nightmare for a game developer who needs maximum GPU
performance. I live in constant fear of bumping the power cord out or needing
to switch rooms. I'm happy to provide any additional information, but glancing
at the amdgpu source code it seems a little over my head!

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