wayland: wrong tiling with wl_drm on Vivante GC2000

[Lucas Stach]

Hi Christian,

Am Donnerstag, dem 30.03.2023 um 19:54 +0000 schrieb Christian Gudrian:
> Hi, Daniel!
> 
> Thanks for your reply.
> 
> > You need to force QtWayland to use the wp-linux-dmabuf-v1 platform
> > integration for the compositor.
> 
> Yes. I've did that before and that indeed solves the tiling problem.
> However the CPU usage is much higher and the FPS drops from 60 to 30
> (I can see a similar behavior with Weston).

etnaviv simply does not have any sideband channel to communicate the
the tiling information, which would be required to make wl_drm work
with tiled buffers. Falling back to linear buffers is also not an
option for performance reasons. etnaviv requires a modifier enabled
interface to get the tiling correct, which in the wayland case is the
linux dmabuf protocol.

If you see a big difference in CPU usage between the two interfaces, it
would be good to investigate where this increased overhead is coming
from to see if we can just fix that.

Regards,
Lucas