[Intel-gfx] [PATCH v5 00/12] Enable GPU switching on pre-retina?MacBook Pro

[Lukas Wunner]

Hi Bastien,

On Tue, Apr 05, 2016 at 06:59:40PM +0200, Bastien Nocera wrote:
> I tested the runtime patches for Radeon on top of 4.6.0-rc2, and
> writing DIGD failed. I also saw a number of messages with the
> vga_switcheroo core in the kernel trying to switch GPUs but failed
> because "client 1" was keeping it busy.
> 
> Is there any way to see what this "client 1" actually is? I'm guessing
> plymouth. In any case, once I'm logged in, the "DIS" is powered and
> used, and the IGD is powered as well.

Client 1 is the discrete GPU, see enum vga_switcheroo_client_id in
include/linux/vga_switcheroo.h:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/linux/vga_switcheroo.h#n75

The vga_switcheroo documentation explains how to find out which
user space process is blocking the switch:
https://01.org/linuxgraphics/gfx-docs/drm/modes_of_use.html

"Prerequisite is that no user space processes (e.g. Xorg, alsactl)
have opened device files of the GPUs or the audio client. If the
switch fails, the user may invoke lsof(8) or fuser(1) on /dev/dri/
and /dev/snd/controlC1 to identify processes blocking the switch."

HTH,

Lukas