On Mon, Sep 14, 2015 at 10:43:51PM +0300, ville.syrjala@linux.intel.com wrote: [...]
@@ -167,7 +238,7 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe, if (!rc) t_vblank = (struct timeval) {0, 0};
- store_vblank(dev, pipe, diff, &t_vblank);
- store_vblank(dev, pipe, diff, &t_vblank, cur_vblank);
I think clearing the t_vblank is now wrong here. This breaks weston on Tegra (and I think all other drivers that don't implement hardware VBLANK timestamps). The reason is that if ->get_vblank_timestamp() isn't implemented, rc will always be false at this point, hence resulting in a zero VBLANK timestamp being reported to userspace.
In fact the comment, reproduced here because it's not in the patch context:
/* * Only reinitialize corresponding vblank timestamp if high-precision query * available and didn't fail. Otherwise reinitialize delayed at next vblank * interrupt and assign 0 for now, to mark the vblanktimestamp as invalid. */
is no longer accurate because this function is now called at the VBLANK interrupt. If you want to keep invalidating timestamps for drivers that implement VBLANK timestamp queries I think the condition needs to be changed to something like:
if (dev->get_vblank_timestamp && !rc)
and the comment updated to reflect the truth. Alternatively this code can be removed, though I guess having the monotonic timestamp fallback would be kind of missing the point.
I've tested either change and they both restore weston on Tegra.
Thierry