Comment # 9 on bug 1177618 from Stefan Dirsch

Thanks.

Xorg.0.log:
[...]
[     9.990] (II) AMDGPU(0): EDID for output HDMI-A-0
[     9.990] (II) AMDGPU(0): Printing probed modes for output HDMI-A-0
[     9.991] (II) AMDGPU(0): Modeline "640x480"x59.9   25.18  640 656 752 800 
480 490 492 525 -hsync -vsync (31.5 kHz e)

dmesg:
[    4.170779] amdgpu 0000:05:00.0: HDMI-A-1: EDID is invalid:
[    4.170781]     [00] BAD  00 ff ff ff ff ff ff 00 04 69 d2 23 52 1d 01 00
[    4.170782]     [00] BAD  18 16 01 03 80 33 1d 78 2a d9 45 a2 55 4d a0 27
[    4.170782]     [00] BAD  00 50 54 b7 ef 00 d1 c0 81 40 81 80 95 00 b3 00
[    4.170782]     [00] BAD  71 4f 81 c0 81 00 02 3a 80 18 71 38 2d 40 58 2c
[    4.170783]     [00] BAD  45 00 fd 1e 11 00 00 1e 00 00 00 ff 00 43 36 4c
[    4.170783]     [00] BAD  4d 54 46 30 37 33 30 34 32 0a 00 00 00 fd 00 32
[    4.170783]     [00] BAD  4b 18 53 11 00 0a 20 20 20 20 20 20 00 00 00 fc
[    4.170784]     [00] BAD  00 41 53 55 53 20 56 53 32 33 39 0a 20 20 01 62
[    4.170910] [drm:dc_link_detect_helper [amdgpu]] *ERROR* EDID checksum
invalid.

No wonder, everything falls back to 640x480 resolution. Since this is working
with different Kernels and on other operating systems
my current guess is, that there exists workarounds for this monitor in
different Kernel/OSes.

Reassigning to kernel component. 

Indeed this is a rather new GPU, so things may improve in the future.

[     9.781] (--) AMDGPU(0): Chipset: "Unknown AMD Radeon GPU" (ChipID =
0x15d8)