[Intel-gfx] [PATCH] drm: Return current vblank value for drmWaitVBlank queries

[Chris Wilson]

On Wed, Mar 18, 2015 at 11:53:16AM +0900, Michel Dänzer wrote:
> drm_vblank_count_and_time() doesn't return the correct sequence number
> while the vblank interrupt is disabled, does it? It returns the sequence
> number from the last time vblank_disable_and_save() was called (when the
> vblank interrupt was disabled). That's why drm_vblank_get() is needed here.

Ville enlightened me as well. I thought the value was cooked so that
time did not pass whilst the IRQ was disabled. Hopefully, I can impress
upon the Intel folks, at least, that enabling/disabling the interrupts
just to read the current hw counter is interesting to say the least and
sits at the top of the profiles when benchmarking Present.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre