AMDGPU without display output

[Deucher, Alexander]

> -----Original Message-----
> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf
> Of Dennis Schridde
> Sent: Thursday, April 13, 2017 10:32 AM
> To: amd-gfx at 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