[Intel-gfx] [PATCH 3/9] drm/i915: use wait_for_vblank instead of msleep(17)

[Daniel Vetter]

17 ms is eerily close to 60 Hz ^-1

Unfortunately this goes back to the original DP enabling for ilk, and
unfortunately does not come with a reason for it's existance attached.

Some closer inspection of the code and DP specs shows that we set the
idle link pattern before we disable the port. And it seems like that
the DP spec (or at least our hw) only switch to the idle pattern on
the next vblank. Hence a vblank wait at this spot makes _much_ more
sense than a really long wait.

v2: Rebase fixup.

Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/intel_dp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index b2aa666..b782094 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1988,6 +1988,8 @@ intel_dp_link_down(struct intel_dp *intel_dp)
 	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
 	struct drm_device *dev = intel_dig_port->base.base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_crtc *intel_crtc =
+		to_intel_crtc(intel_dig_port->base.base.crtc);
 	uint32_t DP = intel_dp->DP;
 
 	/*
@@ -2022,7 +2024,7 @@ intel_dp_link_down(struct intel_dp *intel_dp)
 	}
 	POSTING_READ(intel_dp->output_reg);
 
-	msleep(17);
+	intel_wait_for_vblank(dev, intel_crtc->pipe);
 
 	if (HAS_PCH_IBX(dev) &&
 	    I915_READ(intel_dp->output_reg) & DP_PIPEB_SELECT) {
@@ -2054,7 +2056,7 @@ intel_dp_link_down(struct intel_dp *intel_dp)
 			POSTING_READ(intel_dp->output_reg);
 			msleep(50);
 		} else
-			intel_wait_for_vblank(dev, to_intel_crtc(crtc)->pipe);
+			intel_wait_for_vblank(dev, intel_crtc->pipe);
 	}
 
 	DP &= ~DP_AUDIO_OUTPUT_ENABLE;
-- 
1.7.11.7