-
Mario Kleiner authored
This fixes a regression introduced in Linux 4.4. This is a port of the same fix for radeon-kms in the patch "drm/radeon: Don't hang in radeon_flip_work_func on disabled crtc. (v2)" Limit the amount of time amdgpu_flip_work_func can delay programming a page flip, by both limiting the maximum amount of time per wait cycle and the maximum number of wait cycles. Continue the flip if the limit is exceeded, even if that may result in a visual or timing glitch. This is to prevent a hang of page flips, as reported in fdo bug #93746: Disconnecting a DisplayPort display in parallel to a kms pageflip getting queued can cause the following hang of page flips and thereby an unusable desktop: 1. kms pageflip ioctl() queues pageflip -> queues execution of amdgpu_flip_work_func. 2. Hotunplug of display causes the driver to DPMS OFF the unplugged display. Display engine shuts down, scanout no longer moves, but stays at its resting position at start line of vblank. 3. amdgpu_flip_work_func executes while crtc is off, and due to the non-moving scanout position, the new flip delay code introduced into Linux 4.4 by commit 8e36f9d3 ("drm/amdgpu: Fixup hw vblank counter/ts..") enters an infinite wait loop. 4. After reconnecting the display, the pageflip continues to hang in 3. and the display doesn't update its view of the desktop. This patch fixes the Linux 4.4 regression from fdo bug #93746 <https://bugs.freedesktop.org/show_bug.cgi?id=93746> Reported-by:
Bernd Steinhauser <linux@bernd-steinhauser.de> Signed-off-by:
Mario Kleiner <mario.kleiner.de@gmail.com> Cc: <stable@vger.kernel.org> # 4.4+ Cc: Michel Dänzer <michel.daenzer@amd.com> Cc: Alex Deucher <alexander.deucher@amd.com> Reviewed-by:
Michel Dänzer <michel.daenzer@amd.com> Signed-off-by:
Alex Deucher <alexander.deucher@amd.com>
e1d09dc0