From f8ad028cc033f75fc479ca1c30e2ea4ba56e5269 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Wed, 6 Aug 2014 14:49:49 +0300 Subject: [PATCH] drm: Avoid random vblank counter jumps if the hardware counter has been reset MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When drm_vblank_on() is called the hardware vblank counter may have been reset, so we can't trust that the old values sampled prior to drm_vblank_off() have anything to do with the new values. So update the .last count in drm_vblank_on() to make the first drm_vblank_enable() consider that as the reference point. This will correct the user space visible counter to account for the time between drm_vblank_on() and the first drm_vblank_enable() calls. For extra safety subtract one from the .last count in drm_vblank_on() to make sure that user space will never see the same counter value before and after modeset. Reviewed-by: Matt Roper Reviewed-by: Daniel Vetter Signed-off-by: Ville Syrjälä Signed-off-by: Daniel Vetter --- Reading git-format-patch failed