(release/25.1) modesetting: fix PRESENT_FLIP_REASON_BUFFER_FORMAT gets overwritten#2285
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When dmabuf_capable is enabled, ms_present_check_unflip may return with reason PRESENT_FLIP_REASON_BUFFER_FORMAT to be reported back to client by PresentCompleteModeSuboptimalCopy. We should not overwrite it by page flip reasons anyway when exit. This fix also avoid changing vblank->exec_msc in present_scmd_pixmap() which caused by page flip reasons to prevent a present to be executed immediatly. So that we can cancel pending vblanks when new vblanks with same msc arrive. This happens when application just starts. This problem can be observed at least using radeonsi OGL driver, start xserver with dmabuf_capable enabled, no window manager, glxgears will stuck for the first several seconds. If using a composite window manager like Mutter, we can't observe the glxgears stuck, but the prensent complete event still shows unexpected Copy mode instead of PresentCompleteModeSuboptimalCopy or Skip mode. glxgears window msc is 0 at the beginning, it will send present request with target msc = 1, 2, 3, ... N before server send back the complete event for target msc = 1. But server side window msc is way bigger than N, so it will think all these present requests are outdated and just show the Nth request at the next vblank. [1 .. N-1] requests should be skipped. But without this fix, all [1 .. N] presents will be executed with Copy mode which causes stuck. Fixes: a94dd95 ("modesetting: add support for TearFree page flips") Reviewed-by: Sultan Alsawaf <sultan@kerneltoast.com> Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2091> Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
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When dmabuf_capable is enabled, ms_present_check_unflip may return
with reason PRESENT_FLIP_REASON_BUFFER_FORMAT to be reported back
to client by PresentCompleteModeSuboptimalCopy. We should not
overwrite it by page flip reasons anyway when exit.
This fix also avoid changing vblank->exec_msc in present_scmd_pixmap()
which caused by page flip reasons to prevent a present to be executed
immediatly. So that we can cancel pending vblanks when new vblanks with
same msc arrive. This happens when application just starts.
This problem can be observed at least using radeonsi OGL driver, start
xserver with dmabuf_capable enabled, no window manager, glxgears will
stuck for the first several seconds. If using a composite window manager
like Mutter, we can't observe the glxgears stuck, but the prensent
complete event still shows unexpected Copy mode instead of
PresentCompleteModeSuboptimalCopy or Skip mode.
glxgears window msc is 0 at the beginning, it will send present request
with target msc = 1, 2, 3, ... N before server send back the complete
event for target msc = 1. But server side window msc is way bigger than N,
so it will think all these present requests are outdated and just show the
Nth request at the next vblank. [1 .. N-1] requests should be skipped.
But without this fix, all [1 .. N] presents will be executed with Copy
mode which causes stuck.
Fixes: a94dd95 ("modesetting: add support for TearFree page flips")
Reviewed-by: Sultan Alsawaf sultan@kerneltoast.com
Part-of: https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2091