drm/i915: wait for actual vblank, not just 20ms

Waiting for a hard coded 20ms isn't always enough to make sure a vblank
period has actually occurred, so add code to make sure we really have
passed through a vblank period (or that the pipe is off when disabling).

This prevents problems with mode setting and link training, and seems to
fix a bug like https://bugs.freedesktop.org/show_bug.cgi?id=29278, but
on an HP 8440p instead.  Hopefully also fixes
https://bugs.freedesktop.org/show_bug.cgi?id=29141.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index 5c765bb0845d..093e914e8a41 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -1218,6 +1218,7 @@ static void intel_sdvo_dpms(struct drm_encoder *encoder, int mode)
         struct drm_device *dev = encoder->dev;
         struct drm_i915_private *dev_priv = dev->dev_private;
         struct intel_sdvo *intel_sdvo = enc_to_intel_sdvo(encoder);
+        struct intel_crtc *intel_crtc = to_intel_crtc(encoder->crtc);
         u32 temp;
 
         if (mode != DRM_MODE_DPMS_ON) {
@@ -1240,7 +1241,7 @@ static void intel_sdvo_dpms(struct drm_encoder *encoder, int mode)
                 if ((temp & SDVO_ENABLE) == 0)
                         intel_sdvo_write_sdvox(intel_sdvo, temp | SDVO_ENABLE);
                 for (i = 0; i < 2; i++)
-                  intel_wait_for_vblank(dev);
+                        intel_wait_for_vblank(dev, intel_crtc->pipe);
 
                 status = intel_sdvo_get_trained_inputs(intel_sdvo, &input1, &input2);
                 /* Warn if the device reported failure to sync.