a76dfe350c
drm_atomic_helper_setup_commit expects that flipping of previous commits
has happened when it is called to set up a new commit. This can be violated
by commits where userspace doesn't get a flip completion event to
synchronize against i.e. legacy modesets and property changes.
The expectation is that those are done by blocking commits, which wait for
completion. Most drivers call drm_atomic_helper_wait_for_vblanks in the
commit_tail to ensure completion, but the wait for next vblank might not
actually happen if the commit didn't change any planes.
Make the wait more agressive by also waiting if no planes changed. This
is the minimal regression fix for the 4.15 kernel series. Long term
drivers should switch away from drm_atomic_helper_wait_for_vblanks and
use drm_atomic_helper_wait_for_flip_done instead.
Fixes: de39bec1a0c4 ("drm/atomic: Remove waits in drm_atomic_helper_commit_cleanup_done, v2.")
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171129110431.6300-1-l.stach@pengutronix.de
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.