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Dual GPU dual display support in Debian?

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  Dual GPU dual display support in Debian? Anssi Saari <as@sci.fi> - 2021-09-15 09:20 +0200
    Re: Dual GPU dual display support in Debian? Felix Miata <mrmazda@earthlink.net> - 2021-09-15 09:50 +0200
    Re: Dual GPU dual display support in Debian? Linux-Fan <Ma_Sys.ma@web.de> - 2021-09-15 12:00 +0200
      Re: Dual GPU dual display support in Debian? Anssi Saari <as@sci.fi> - 2021-09-15 13:30 +0200
        Re: Dual GPU dual display support in Debian? Linux-Fan <Ma_Sys.ma@web.de> - 2021-09-15 16:30 +0200

#239998 — Dual GPU dual display support in Debian?

I was wondering, since I didn't really find anything definite via Google
but is dual GPU dual display actually a supported configuration in
Debian 11?

So basically for a while I ran this kind of setup:

Display 1 connected to CPU's integrated GPU (Core i7-4790K, Intel HD
Graphics 4600).

Display 2 connected to Nvidia RTX3070Ti.

The two displays setup as a single wide display, i.e. windows
movable/draggable from one display to the other. 

I have a triple boot setup, Windows 10 worked fine, Arch Linux with KDE
was hit or miss, Debian didn't work, no image on one display and xrandr
saw only one display. Which one seemed to depend on which GPU was set as
primary in the UEFI setup. No xorg.conf but I fiddled with that too.

Each OS used Nvidia's proprietary driver since there isn't much anything
else for such a new GPU. My minimal video card support is accelerated 2D
and 3D and video decoding so wasn't looking for just any video output.

The reason for this setup was that Debian 10 has no drivers for the
RTX3070Ti so I just used one display there and since it worked in Arch
(at least sometimes) I figured it should just start working in Debian 11
after the upgrade but it didn't.

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#240000

Anssi Saari composed on 2021-09-15 10:15 (UTC+0300):
 
> I was wondering, since I didn't really find anything definite via Google
> but is dual GPU dual display actually a supported configuration in
> Debian 11?
 
> So basically for a while I ran this kind of setup:
 
> Display 1 connected to CPU's integrated GPU (Core i7-4790K, Intel HD
> Graphics 4600).
 
> Display 2 connected to Nvidia RTX3070Ti.
 
> The two displays setup as a single wide display, i.e. windows
> movable/draggable from one display to the other. 
											
Why aren't you plugging all displays into the NVidia? Even IGPs can support
3 displays as one screen right out of the box.

# inxi -SGayz
System:
  Kernel: 5.10.0-8-amd64 x86_64 bits: 64 compiler: gcc v: 10.2.1...
  Desktop: Trinity R14.0.11 tk: Qt 3.5.0 info: kicker wm: Twin 3.0 vt: 7
  dm: TDM Distro: Debian GNU/Linux 11 (bullseye)
Graphics:
  Device-1: Intel HD Graphics 630 vendor: Gigabyte driver: i915 v: kernel
  bus-ID: 00:02.0 chip-ID: 8086:5912 class-ID: 0300
  Display: x11 server: X.Org 1.20.11 driver: loaded: modesetting
  unloaded: fbdev,vesa display-ID: :0 screens: 1
  Screen-1: 0 s-res: 2560x3720 s-dpi: 120 s-size: 541x787mm (21.3x31.0")
  s-diag: 955mm (37.6")
  Monitor-1: HDMI-1 res: 2560x1080 hz: 60 dpi: 97 size: 673x284mm (26.5x11.2")
  diag: 730mm (28.8")
  Monitor-2: HDMI-2 res: 1920x1200 hz: 60 dpi: 94 size: 519x324mm (20.4x12.8")
  diag: 612mm (24.1")
  Monitor-3: DP-1 res: 2560x1440 hz: 60 dpi: 109 size: 598x336mm (23.5x13.2")
  diag: 686mm (27")
  OpenGL: renderer: Mesa Intel HD Graphics 630 (KBL GT2) v: 4.6 Mesa 20.3.5
  direct render: Yes
# xrandr | egrep 'onnect|creen|\*' | grep -v disconn | sort -r
Screen 0: minimum 320 x 200,

        current 2560 x 3720, maximum 16384 x 16384

HDMI-2 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 519mm x 324mm
HDMI-1 connected 2560x1080+0+1200 (normal left inverted right x axis y axis) 673mm x 284mm
DP-1 connected primary 2560x1440+0+2280 (normal left inverted right x axis y axis) 598mm x 336mm
   2560x1440     59.95*+  74.92
   2560x1080     60.00*+
   1920x1200     59.95*+
-- 
Evolution as taught in public schools is, like religion,
	based on faith, not based on science.

 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata

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#240003

[Multipart message — attachments visible in raw view] — view raw

Anssi Saari writes:

> I was wondering, since I didn't really find anything definite via Google
> but is dual GPU dual display actually a supported configuration in
> Debian 11?

I would be interested in knowing about that, too.

> So basically for a while I ran this kind of setup:
>
> Display 1 connected to CPU's integrated GPU (Core i7-4790K, Intel HD
> Graphics 4600).
>
> Display 2 connected to Nvidia RTX3070Ti.
>
> The two displays setup as a single wide display, i.e. windows
> movable/draggable from one display to the other.
>
> I have a triple boot setup, Windows 10 worked fine, Arch Linux with KDE
> was hit or miss, Debian didn't work, no image on one display and xrandr
> saw only one display. Which one seemed to depend on which GPU was set as
> primary in the UEFI setup. No xorg.conf but I fiddled with that too.

[...]

> The reason for this setup was that Debian 10 has no drivers for the
> RTX3070Ti so I just used one display there and since it worked in Arch
> (at least sometimes) I figured it should just start working in Debian 11
> after the upgrade but it didn't.

I believe it might be easier to fix the problem by attaching all displays to  
the NVidia GPU. Here are some hints about what you might check to make the  
NVidia GPU work under Debian 11:

https://forums.developer.nvidia.com/t/linux-460-driver-kubuntu-20-04-rtx-3070-not-booting/171085

About doing a "dual GPU dual display" my experience is as follows (from  
Debian 10 oldstable/buster with purely X11 and no Wayland):

First, I never got it to work properly.

Closest I could get was to run two different window managers on the  
respective displays all under the same X server. This allowed the mouse and  
clipboard to move across the screens but the windows needed to remain on the  
GPU they were started on. Additionally, one cannot combine arbitrary window  
managers this way - I used i3 and IceWM. The trick is to not have them  
compete for "focus". The `.xsession` looked as follows:

	DISPLAY=:0.1 icewm &
	exec i3

IIRC there were also some approaches like starting an X-server on top of the  
two X11 displays (:0.1 etc.) but I cannot seem to find them right now. Back  
when I tried that setup, it seemed these would be unable to provide graphics  
accelleration, hence I opted for the more convoluted variant with two window  
managers and full performance.

HTH
Linux-Fan

öö

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#240007

Linux-Fan <Ma_Sys.ma@web.de> writes:

> Anssi Saari writes:
>
>> I was wondering, since I didn't really find anything definite via Google
>> but is dual GPU dual display actually a supported configuration in
>> Debian 11?
>
> I would be interested in knowing about that, too.

I wonder if this is a kernel space problem or user space or both? So
does it work in Arch Linux because the Nvidia drivers and Linux kernel
are much newer? Or is there some user space component too that matters?

>> So basically for a while I ran this kind of setup:

> I believe it might be easier to fix the problem by attaching all
> displays to the NVidia GPU. Here are some hints about what you might
> check to make the NVidia GPU work under Debian 11:

Thanks, but a hint to you and Felix: "for a while I ran..." indicates
something happening in the past which has now ended. I have no current
issues for basic use. I haven't actually tried to do accelerated video
encode with the new video card which I count as advanced use but I need
it so rarely it hasn't come up.

> https://forums.developer.nvidia.com/t/linux-460-driver-kubuntu-20-04-rtx-3070-not-booting/171085

I think that specific issue was fixed earlier, at least I remember
reading a long thread that was specifically related to DP outputs and
from last spring.

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#240014

[Multipart message — attachments visible in raw view] — view raw

Anssi Saari writes:

> Linux-Fan <Ma_Sys.ma@web.de> writes:
>
> > Anssi Saari writes:
> >
> >> I was wondering, since I didn't really find anything definite via Google
> >> but is dual GPU dual display actually a supported configuration in
> >> Debian 11?
> >
> > I would be interested in knowing about that, too.
>
> I wonder if this is a kernel space problem or user space or both? So
> does it work in Arch Linux because the Nvidia drivers and Linux kernel
> are much newer? Or is there some user space component too that matters?

AFAIK there are at least these components involved:

 * Kernel
 * Proprietary graphics driver (kernel- and userspace parts, NVidia)
 * Mesa (userspace)

I am not sure how much "cooperation" from the X server itself is required  
i.e. if it might be enough to build a newer Mesa but keep running an old X 
server.

> >> So basically for a while I ran this kind of setup:
>
> > I believe it might be easier to fix the problem by attaching all
> > displays to the NVidia GPU. Here are some hints about what you might
> > check to make the NVidia GPU work under Debian 11:
>
> Thanks, but a hint to you and Felix: "for a while I ran..." indicates
> something happening in the past which has now ended. I have no current
> issues for basic use. I haven't actually tried to do accelerated video
> encode with the new video card which I count as advanced use but I need
> it so rarely it hasn't come up.

OK

[...]

Linux-Fan
öö

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