modesetting: Disable pageflipping when using a swcursor

The miPointerSpriteFunc swcursor code expects there to only be a single
framebuffer and when the cursor moves it will undo the damage of the
previous draw, potentially overwriting what ever is there in a new
framebuffer installed after a flip.

This leads to all kind of artifacts, so we need to disable pageflipping
when a swcursor is used.

The code for this has shamelessly been copied from the xf86-video-amdgpu

Fixes: xorg/xserver#828

Reviewed-by: Michel Dänzer <>
Signed-off-by: Hans de Goede <>
(cherry picked from commit 0aaac8d7)
Signed-off-by: Łukasz Spintzyk <>
3 jobs for lspintzyk/sw_cursor_support_merge in 4 minutes and 43 seconds (queued for 1 second)