modesetting hooked up vblank support for DRI2, but was missing support
for vblanks in Present.
This is mostly copy and pasted from Keith's code in the intel driver.
v2: Use ms_crtc_msc_to_kernel_msc in ms_present_queue_vblank to hook
up the vblank_offset workaround for bogus MSC values (which the
DRI2 code already did).
Also simplify the ms_present_get_crtc function. vblank.c already
implements the functionality; we just need to convert types.
v3: Fix ms_flush_drm_events return code. I'd copied code where 0 meant
success into a function that returned a boolean, so the return code
was always backwards.
Also add DebugPresent calls in ms_present_vblank_{handler,abort}.
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Keith Packard <keithp@keithp.com>
Tested-by: Jason Ekstrand <jason.ekstrand@intel.com>
Signed-off-by: Keith Packard <keithp@keithp.com>
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