drm_vblank_count() has an u32 type returning what is a 64-bit vblank count.
The effect of this is when drm_wait_vblank_ioctl() tries to widen the user
space requested vblank sequence using this clipped 32-bit count(when the
value is >= 2^32) as reference, the requested sequence remains a 32-bit
value and gets queued like that. However, the code that checks if the
requested sequence has passed compares this against the 64-bit vblank
count.

With drm_vblank_count() returning all bits of the vblank count, update
drm_crtc_accurate_vblank_count() so that drm_crtc_arm_vblank_event() queues
the correct sequence. Otherwise, this leads to prolonged waits for a vblank
sequence when the current count is >=2^32.

Finally, fix drm_wait_one_vblank() too.

v2: Commit message fix (Keith)
    Squash commits (Rodrigo)

Fixes: 570e8696 ("drm: Widen vblank count to 64-bits [v3]")
Cc: Keith Packard <keithp@keithp.com>
Cc: Michel Dänzer <michel@daenzer.net>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180203051302.9974-1-dhinakaran.pandiyan@intel.com