[Bug 200695] Blank screen on RX 580 with amdgpu.dc=1 enabled (no displays detected)

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=200695

Lukas Fink (lukas.fink1 at gmail.com) changed:

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                 CC|                            |lukas.fink1 at gmail.com

--- Comment #43 from Lukas Fink (lukas.fink1 at gmail.com) ---
(In reply to babgozd from comment #38)
> I am following this thread since it has created. My R9 380 with DVI-I output
> is connected to my VGA monitor with DVI-I male to VGA female adapter and I
> am getting black/blank screen while booting with amdgpu.dc=1 which is
> default since kernel 4.17. It is fine with amdgpu.dc=0. I can provide logs
> too if any kernel contributor wants to investigate the problem any further.

To me it seems, as if the DVI-I port is somehow misdetected/misconfigured as a
DVI-D port. With dc=0 I find the files "card1-DVI-I-1" and "card1-DVI-D-1" in
"/sys/class/drm/card1". With dc=1 there are "card1-DVI-D-1" and
"card1-DVI-D-2".

It appears to correctly negotiate resolution and refresh rate over DDC, but
because it only outputs the digital signal, a display connected over VGA
receives nothing and turns off.

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