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[ Upstream commit 9e4dde28e9cd34ee13a6b7247f0857fb49fd3f19 ] Someone on IRC once asked an innocent enough sounding question: Why with xf86-video-modesetting is es2gears limited at 120fps. So I broke out the perfetto tracing mesa MR and took a look. It turns out the problem was drm_atomic_helper_dirtyfb(), which would end up waiting for vblank.. es2gears would rapidly push two frames to Xorg, which would blit them to screen and in idle hook (I assume) call the DIRTYFB ioctl. Which in turn would do an atomic update to flush the dirty rects, which would stall until the next vblank. And then the whole process would repeat. But this is a bit silly, we only need dirtyfb for command mode DSI panels. So track in plane state whether dirtyfb is required, and track in the fb how many attached planes require dirtyfb so that we can skip it when not required. (Note, mdp4 does not actually have cmd mode support.) Signed-off-by: Rob Clark <robdclark@chromium.org> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> Link: https://lore.kernel.org/r/20220223191118.881321-1-robdclark@gmail.com Signed-off-by: Rob Clark <robdclark@chromium.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.