Bug 203339

Summary:	AMDGPU: virtual_display disables physical outputs
Product:	Drivers	Reporter:	Parker Reed (parker.l.reed)
Component:	Video(DRI - non Intel)	Assignee:	drivers_video-dri
Status:	NEW ---
Severity:	normal	CC:	alexdeucher, jjmarr, kernel.org, stephen.searles, t.clastres, vita.amaro
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	5.0.7	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	Kernel log

Description Parker Reed 2019-04-16 22:51:52 UTC

Created attachment 282351 [details]
Kernel log

Unable to tell if this is intended or if caused by a crash.

I have a monitor connected via HDMI. When I use the virtual_display kernel parameter, only the virtual displays show up.

amdgpu.virtual_display=0000:07:00.0,2

Original patchset doesn't mention this usecase.

https://lists.freedesktop.org/archives/amd-gfx/2016-August/001058.html

Kernel log attached shows some crashes related to dce_virtual_crtc

Comment 1 Alex Deucher 2019-04-17 04:05:34 UTC

(In reply to Parker Reed from comment #0)
> 
> I have a monitor connected via HDMI. When I use the virtual_display kernel
> parameter, only the virtual displays show up.

When you enable the virtual display option the real displays are disabled.  That is the intended behavior.  It's not a crash just a warning.

Comment 2 Drath 2020-09-02 15:18:18 UTC

>When you enable the virtual display option the real displays are disabled. 
>That is the intended behavior.

Why, though? Is it necessary part of this functionality or is it just a failsafe?

Comment 3 Alex Deucher 2020-09-02 16:00:19 UTC

(In reply to Drath from comment #2)
> >When you enable the virtual display option the real displays are disabled. 
> >That is the intended behavior.
> 
> Why, though? Is it necessary part of this functionality or is it just a
> failsafe?

It's a lot of work to make them all work together and it has not been implemented.  Plus for he main uses of virtual displays (virtualized GPUs and early bring up and emulation), there is no physical display hardware available or it's not ready to be used.

Comment 4 vita.amaro@gmail.com 2020-10-21 08:57:56 UTC

But what if i need virtual display in order to use it as a second monitor via vnc? There is no way...

Comment 5 Alex Deucher 2020-10-21 12:47:00 UTC

(In reply to vita.amaro@gmail.com from comment #4)
> But what if i need virtual display in order to use it as a second monitor
> via vnc? There is no way...

Patches welcomed.