Can't get VGA video on Carrizo R7 gpu, only HDMI

[Alex Deucher]

On Mon, Oct 28, 2019 at 1:21 PM MONSSA <debian at monssa.com.ar> wrote:
>
> Hello. This is my first time trying to report a bug, I hope I'm in the
> right place.
>
> I have a PC with MSI A68HM-E33 V2 motherboard, and AMD A8-7680 CPU with
> Radeon R7.
>
> I'm running Debian 9 Stretch, Kernel~4.19.0-0.bpo.6-amd64, using amdgpu
> driver, and I get video only on the HDMI output.
>
> xrandr only lists the HDMI output as connected, and a DVI output
> disconnected. The motherboard doesn't have DVI connector, only VGA and HDMI.
>
> I tried forcing video output on the DVI interface, but I didn't get any
> video on VGA port, even though the desktop was arranged to spread across
> both screens.
>
> I tried several options for the kernel module, such as "exp_hw_support"
> and "cik_support" didn't fully knowing what they did, to no avail.
>
> Of course I have two monitors plugged in to both connectors, and I ruled
> out hardware problems (such as burned connector) because I changed the
> HDD and installed windows, with the official AMD windows drivers I get
> video working fine on both monitors, so monitors, cables and ports are
> working.

I would suggest opening a bug (https://bugs.freedesktop.org) and
attaching your dmesg output and Xorg log (if using X).  Please also
attach a copy of your vbios (sudo cat
/sys/kernel/debug/dri/0/amdgpu_vbios > /tmp/vbios.rom).  VGA is
usually implemented via a DP bridge chip since that chip does not
support analog outputs directly.

Alex