Bug Report: [PowerPlay] MCLK can't be set above 1107MHz on Vega 64

[Yanik Yiannakis]

Hello,

I experience a bug that prevents me from setting the MCLK of my Vega 64 
LC above 1107MHz.

I am using Unigine Superposition 1.1 in "Game"-mode to check the 
performance by watching the FPS.


*Behaviour with a single monitor:*

First I set the MCLK to a known stable value below 1108MHz:

/$ echo "m 3 1100 950" > 
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/pp_od_clk_voltage 
/

In Unigine Superposition the FPS increase as expected.

pp_dpm_mclk also confirms the change.

/$ watch cat 
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/pp_dpm_mclk/

    0: 167Mhz
    1: 500Mhz
    2: 800Mhz
    3: 1100Mhz *


After that I set the MCLK to a stable value above 1107MHz:

/$ echo "m 3 1200 950" > 
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/pp_od_clk_voltage 
/

In Unigine Superposition the FPS drop drastically.

pp_dpm_mclk indicates that the MCLK is stuck in state 0 (167MHz):

    0: 167Mhz *
    1: 500Mhz
    2: 800Mhz
    3: 1200Mhz


*Behaviour with multiple monitors that have different refresh rates:*

My monitors have different refresh rates. This causes the MCLK to stay 
in state 3 (945MHz stock) which is the expected behaviour as I 
understand it.


Now I try to set the MCLK to a value above 1107MHz:

/$ echo "m 3 1200 950" > 
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/pp_od_clk_voltage 
/

The FPS in Unigine Superposition remain the same as they were with 945MHz.

pp_dpm_mclk shows however that the value was set:

    0: 167Mhz
    1: 500Mhz
    2: 800Mhz
    3: 1200Mhz *


Then I set the MCLK to a value of 1107MHz or lower:

/$ echo "m 3 1100 950" > 
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/pp_od_clk_voltage 
/

The FPS in Unigine Superposition *increase*.

pp_dpm_mclk again confirms the set value:

    0: 167Mhz
    1: 500Mhz
    2: 800Mhz
    3: 1100Mhz *


Finally I increase MCLK to a known unstable value:

/$ echo "m 3 1300 950" > 
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/pp_od_clk_voltage 
/

The FPS in Unigine Superposition remain the same. I therefore believe 
the value was not actually applied.

However pp_dpm_mclk shows that it was:

    0: 167Mhz
    1: 500Mhz
    2: 800Mhz
    3: 1300Mhz *


amdgpu_pm_info also claims that the value was set:

/$ sudo watch cat /sys/kernel/debug/dri/1/amdgpu_pm_info/

    GFX Clocks and Power:
             1300 MHz (MCLK)
             27 MHz (SCLK)
             1348 MHz (PSTATE_SCLK)
             800 MHz (PSTATE_MCLK)
             825 mV (VDDGFX)
             4.0 W (average GPU)

Again, I think the displayed MCLK is false and the memory still runs at 
1100MHz because the performance in Unigine Superposition indicates this 
and 1300MHz would cause a crash immediately.

A stable value (e.g. 1200MHz) causes the same behaviour. I just chose 
1300MHz to be sure.



Tested on these Kernels:

    Arch-Linux 5.0.9 (Arch)

    Linux 5.1-rc6 (Ubuntu)

    Linux 5.0 with amd-staging-drm-next (Ubuntu)
    (https://github.com/M-Bab/linux-kernel-amdgpu-binaries)

(Same behaviour on every kernel.)


Tested on this hardware:

    CPU: Intel i7-8700k

    Motherboard: MSI Z370 Gaming Pro Carbon

    GPU: Powercolor Vega 64 Liquid Cooled (Memory stable below 1220MHz,
    tested on Windows 10 with Wattman and Unigine Superposition)


Unigine Superposition "Game"-Mode settings:

    Preset: Custom

    Fullscreen: Disabled

    Resolution: 3840x2160 (4K UHD)

    Shaders Quality: Extreme

    Textures Quality: High

    Vsync: Off

    Depth of Field: On

    Motion Blur: On


I hope this helps.

Yanik Yiannakis

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