AMDGPU without display output

AMDGPU without display output

[Dennis Schridde]

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Hello again!

I am trying to use a AMD FirePro S7150X2 with the AMDGPU driver of a Linux 
4.10.9 kernel (CoreOS Container Linux) and linux-firmware 
e39f0e3e6897ad865b3704f61218ae83f98a85da.

Since the card has no display output and I want to run remote applications 
only, I would like to prevent any interference with mode setting and the 
kernel console. Thus I set "nomodeset" on the kernel command line to prevent 
the kernel from trying to initialise anything but the rendering functions of 
the card. However, this leads to following error message:

[drm:init_module [amdgpu]] *ERROR* VGACON disables amdgpu kernel modesetting.

The result is that the AMDGPU module can not be loaded.

Is this generally the right approach to use this driver for rendering without 
display output, or can I safely leave KMS enabled and it will not interfere 
with my application's X servers and the OpenGL applications running on them?

Assuming I have to disable KMS, how would I get past this error, i.e. to 
initialise the card's rendering functions, but skipping initialisation of the 
output part of the driver?

Generally asking: How do people use this card for GPGPU compute (i.e. 
headless) tasks? Is there some documentation what I need to pay attention to?

Thanks,
Dennis

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RE: AMDGPU without display output

[Deucher, Alexander]

> -----Original Message-----
> From: amd-gfx [mailto:amd-gfx-bounces@lists.freedesktop.org] On Behalf
> Of Dennis Schridde
> Sent: Thursday, April 13, 2017 10:32 AM
> To: amd-gfx@lists.freedesktop.org
> Subject: AMDGPU without display output
> 
> Hello again!
> 
> I am trying to use a AMD FirePro S7150X2 with the AMDGPU driver of a Linux
> 4.10.9 kernel (CoreOS Container Linux) and linux-firmware
> e39f0e3e6897ad865b3704f61218ae83f98a85da.
> 
> Since the card has no display output and I want to run remote applications
> only, I would like to prevent any interference with mode setting and the
> kernel console. Thus I set "nomodeset" on the kernel command line to
> prevent
> the kernel from trying to initialise anything but the rendering functions of
> the card. However, this leads to following error message:
> 
> [drm:init_module [amdgpu]] *ERROR* VGACON disables amdgpu kernel
> modesetting.
> 
> The result is that the AMDGPU module can not be loaded.

nomodeset prevents the driver from loading.  It's a way to disable the KMS altogether.

> 
> Is this generally the right approach to use this driver for rendering without
> display output, or can I safely leave KMS enabled and it will not interfere
> with my application's X servers and the OpenGL applications running on
> them?
> 

The driver only exposes display connectors when they exist.

> Assuming I have to disable KMS, how would I get past this error, i.e. to
> initialise the card's rendering functions, but skipping initialisation of the
> output part of the driver?
> 

You don't have disable KMS.  there is no way to.  The driver will expose the hw that exists on the card.  If there are not display connectors, none will be exposed.  It's up to the user to configure X to use or not use specific cards.

> Generally asking: How do people use this card for GPGPU compute (i.e.
> headless) tasks? Is there some documentation what I need to pay attention
> to?

It should just work as long as the driver is loaded.

Alex

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Re: AMDGPU without display output

[Dennis Schridde]

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Thanks, Alex!

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Re: AMDGPU without display output

[Yu, Qiang]

PS. If you want to use X11/OGL on this no display output card, just add an option to
the amdgpu kernel module "virtual_display=all" which will fake a display output so that
the xserver can start with amdgpu DDX successfully. You can use remote desktop apps
like VNC to view the X screen.

Regards,
Qiang
________________________________________
From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> on behalf of Dennis Schridde <dennis.schridde@uni-heidelberg.de>
Sent: Thursday, April 13, 2017 11:20:22 PM
To: amd-gfx@lists.freedesktop.org
Cc: Deucher, Alexander
Subject: Re: AMDGPU without display output

Thanks, Alex!
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Re: AMDGPU without display output

[Dennis Schridde]

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On Freitag, 14. April 2017 03:50:30 CEST Yu, Qiang wrote:
> PS. If you want to use X11/OGL on this no display output card, just add an
> option to the amdgpu kernel module "virtual_display=all" which will fake a
> display output so that the xserver can start with amdgpu DDX successfully.
> You can use remote desktop apps like VNC to view the X screen.

Thanks a lot for that information! This will likely simplify several things, 
once we solve the "Fatal error during GPU init" (see my other email).

--Dennis

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