How to force the kernel boot messages on a given output on a GPU (or on all outputs)?

by Nico   Last Updated February 04, 2017 15:00 PM - source

I use 2 GPUs on a machine (GTX770), and I have 2 screens connected to the 2 outputs (DVI1 and DVI2). I CANNOT decide to plug a screen on one GPU and the other on the other GPU (for good reasons... ;-) ).

Let's name MS the main screen: the end-user interact with it. Let's name TS the other screen (technical screen, which is used by our system for technical stuff).

My issue: when the system boot (Linux version 3.1.9-1.4-desktop ([email protected]) (gcc version 4.6.2 (SUSE Linux) ), sometime the kernel boot messages are displayed on MS, some other time, they are displayed on TS.

I want they are always displayed on MS, because when the boot fails, I can't afford the user being in front of a black screen (the emergency mode is display on TS, not visible by end-user).

Some additional information: - I speak about the messages of the kernel, before X is started. - When the boot messages are displayed on TS, I have that in Xorg log:

[ 17.203] (--) NVIDIA(0): Valid display device(s) on GPU-0 at PCI:2:0:0
[ 17.203] (--) NVIDIA(0): CRT-0
[ 17.203] (--) NVIDIA(0): DFP-0
[ 17.203] (--) NVIDIA(0): DFP-1
[ 17.203] (--) NVIDIA(0): DFP-2
[ 17.203] (--) NVIDIA(0): DFP-3 (boot)
[ 17.203] (--) NVIDIA(0): DFP-4

and I have check that DFP-3 is the TS (through nvidia-settings: if I change color curves of DFP-3, TS is impacted). - When the boot messages are displayed on MS, I have that in Xorg log:

[ 17.203] (--) NVIDIA(0): Valid display device(s) on GPU-0 at PCI:2:0:0
[ 17.203] (--) NVIDIA(0): CRT-0
[ 17.203] (--) NVIDIA(0): DFP-0
[ 17.203] (--) NVIDIA(0): DFP-1
[ 17.203] (--) NVIDIA(0): DFP-2
[ 17.203] (--) NVIDIA(0): DFP-3 (boot)
[ 17.203] (--) NVIDIA(0): DFP-4

=> THE SAME I'm not sure but I believe that the motherboard splash screen was displayed on TS in both cases above. But sometime its is displayed on MS (I don't have the Xorg logs of that case).

In both above cases, DFP-3 is the same screen (TS):

[ 17.888] (--) NVIDIA(0): DFP-3 Name Aliases:
[ 17.888] (--) NVIDIA(0): DFP
[ 17.888] (--) NVIDIA(0): DFP-3
[ 17.888] (--) NVIDIA(0): DPY-10
[ 17.888] (--) NVIDIA(0): DVI-D-0
[ 17.888] (--) NVIDIA(0): DVI-D-0

Here I am lost: I would say that, because NVIDIA naming seems stable, it may be the BIOS that send a parameters different ... but I don't know. Maybe the screens "hello i'm here, my name is... and my edid is..." messages order is not stable, and the NVIDIA device select the first output receiving the "hello" as "boot output"...

What I'd like to achieve: - either be able to fix a given output for boot messages (DVI-D-0) - or display the boot messages on both screens.

Thanks if you read me until here. Thanks 1000x if you have a solution!!

I tried some kernel options (for instance video=DVI-D-0:d) but in vain.

Of course if you need more configuration details I'm available!



Answers 1


I am getting something similar.

I have two NVidia cards:

  1. GeForce GTX 960, with two monitors plugged in:
    • DP-4: ASUS PB287Q
    • HDMI-0: Samsung (KS-8000)
  2. GeForce GTX 560 Ti, with no monitors plugged in. It is also disabled in X (/etc/X11/xorg.conf), and doesn't invervene.

During boot, I am not getting any display signal to the main monitor (PB287Q, plugged into Displayport-4). I need to use the Samsung TV to observe the boot sequence.

Additionally, when the X window manager (lightdm, as I am on Ubuntu 16.04) starts, it always defaults to the Samsung TV, despite my attempts to force the Asus Monitor as primary (in xorg.conf, and with nvidia-settings configuration tool), and have both displays mirror each other indifferently.

The Asus monitor has an option to select between "DisplayPort Stream" 1.1 or 1.2. I thought that selecting 1.2 would help to identify it as the primary monitor. Unfortunately, this doesn't work at all.

The boot sequence display is sent to the DisplayPort if, and only if, the HDMI is unplugged (even if the screen is not powered).

Dan0
Dan0
January 27, 2017 02:14 AM

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