Comment 9 for bug 1420290

FWIW: I searched for "[drm:intel_pipe_update_end [i915]] *ERROR* Atomic update failure on pipe A (start=76355 end=76356)" and found this source code on http://lists.freedesktop.org/archives/intel-gfx/2014-February/040161.html doing the "Atomic update failure on pipe":

115 static void intel_pipe_update_end(struct intel_crtc *crtc, u32 start_vbl_count)
116 {
117 struct drm_device *dev = crtc->base.dev;
118 enum pipe pipe = crtc->pipe;
119 u32 end_vbl_count = dev->driver->get_vblank_counter(dev, pipe);
120
121 trace_i915_pipe_update_end(crtc, end_vbl_count);
122
123 local_irq_enable();
124
125 if (start_vbl_count != end_vbl_count)
126 DRM_ERROR("Atomic update failure on pipe %c (start=%u end=%u)\n",
127 pipe_name(pipe), start_vbl_count, end_vbl_count);
128 }

So because start_vbl_count != end_vbl_count I get that message in dmesg.

NB: I'm not sure the message "[drm:intel_pipe_update_end [i915]] *ERROR* Atomic update failure on pipe A (start=76355 end=76356)" has to do with the error message 12 seconds later "WARNING: CPU: 0 PID: 0 at /home/kernel/COD/linux/drivers/gpu/drm/i915/intel_display.c:9698 intel_check_page_flip+0xe6/0xf0 [i915]()"