[PATCH 4/4] drm/i915: skip useless vblank wait on Haswell audio sequence

[Paulo Zanoni <przanoni@gmail.com>]

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

We call haswell_write_eld at mode_set time, not at crtc_enable time,
so the pipes are stopped, and it doesn't really make sense to wait for
a vblank: it just delays the modeset in 50ms.

Leave the code there (commented with FIXME) for now since maybe we
need a bigger rework.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 69e8bb6..b891a0c 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6662,7 +6662,6 @@ static void haswell_write_eld(struct drm_connector *connector,
 {
 	struct drm_i915_private *dev_priv = connector->dev->dev_private;
 	uint8_t *eld = connector->eld;
-	struct drm_device *dev = crtc->dev;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	uint32_t eldv;
 	uint32_t i;
@@ -6684,8 +6683,17 @@ static void haswell_write_eld(struct drm_connector *connector,
 	tmp |= (AUDIO_OUTPUT_ENABLE_A << (pipe * 4));
 	I915_WRITE(aud_cntrl_st2, tmp);
 
-	/* Wait for 1 vertical blank */
-	intel_wait_for_vblank(dev, pipe);
+	/*
+	 * Wait for 1 vertical blank
+	 *
+	 * FIXME: We call this function at mode_set time, when the pipes are all
+	 * stopped, so it doesn't really make any sense to wait for a vblank
+	 * here: it just delays the modeset in 50ms. I'll leave the code here
+	 * because since the wait doesn't make sense at this point, maybe we
+	 * need a bigger rework. We need an Audio authority to audit this code.
+	 *
+	 * intel_wait_for_vblank(dev_priv->dev, pipe);
+	 */
 
 	/* Set ELD valid state */
 	tmp = I915_READ(aud_cntrl_st2);
-- 
1.8.3.1