drm/i915: Fix the IBX transcoder B workarounds

Currently the IBX transcoder B workarounds are not working correctly.
Well, the HDMI one seems to be working somewhat, but the DP one is
definitely busted.

After a bit of experimentation it looks like the best way to make this
work is first disable the port on transcoder B, and then re-enable it
transcoder A, and immediately disable it again.

We can also clean up the code by noting that we can't be called without
a valid crtc. And also note that port A on ILK does not need the
workaround, so let's check for that one too.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 21 insertions, 16 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index d86e1f951666..abd442af4127 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3843,6 +3843,7 @@ static void
 intel_dp_link_down(struct intel_dp *intel_dp)
 {
 	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+	struct intel_crtc *crtc = to_intel_crtc(intel_dig_port->base.base.crtc);
 	enum port port = intel_dig_port->port;
 	struct drm_device *dev = intel_dig_port->base.base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -3859,34 +3860,38 @@ intel_dp_link_down(struct intel_dp *intel_dp)
 	if ((IS_GEN7(dev) && port == PORT_A) ||
 	    (HAS_PCH_CPT(dev) && port != PORT_A)) {
 		DP &= ~DP_LINK_TRAIN_MASK_CPT;
-		I915_WRITE(intel_dp->output_reg, DP | DP_LINK_TRAIN_PAT_IDLE_CPT);
+		DP |= DP_LINK_TRAIN_PAT_IDLE_CPT;
 	} else {
 		if (IS_CHERRYVIEW(dev))
 			DP &= ~DP_LINK_TRAIN_MASK_CHV;
 		else
 			DP &= ~DP_LINK_TRAIN_MASK;
-		I915_WRITE(intel_dp->output_reg, DP | DP_LINK_TRAIN_PAT_IDLE);
+		DP |= DP_LINK_TRAIN_PAT_IDLE;
 	}
+	I915_WRITE(intel_dp->output_reg, DP);
 	POSTING_READ(intel_dp->output_reg);
 
-	if (HAS_PCH_IBX(dev) &&
-	    I915_READ(intel_dp->output_reg) & DP_PIPEB_SELECT) {
-		/* Hardware workaround: leaving our transcoder select
-		 * set to transcoder B while it's off will prevent the
-		 * corresponding HDMI output on transcoder A.
-		 *
-		 * Combine this with another hardware workaround:
-		 * transcoder select bit can only be cleared while the
-		 * port is enabled.
-		 */
-		DP &= ~DP_PIPEB_SELECT;
+	DP &= ~(DP_PORT_EN | DP_AUDIO_OUTPUT_ENABLE);
+	I915_WRITE(intel_dp->output_reg, DP);
+	POSTING_READ(intel_dp->output_reg);
+
+	/*
+	 * HW workaround for IBX, we need to move the port
+	 * to transcoder A after disabling it to allow the
+	 * matching HDMI port to be enabled on transcoder A.
+	 */
+	if (HAS_PCH_IBX(dev) && crtc->pipe == PIPE_B && port != PORT_A) {
+		/* always enable with pattern 1 (as per spec) */
+		DP &= ~(DP_PIPEB_SELECT | DP_LINK_TRAIN_MASK);
+		DP |= DP_PORT_EN | DP_LINK_TRAIN_PAT_1;
+		I915_WRITE(intel_dp->output_reg, DP);
+		POSTING_READ(intel_dp->output_reg);
+
+		DP &= ~DP_PORT_EN;
 		I915_WRITE(intel_dp->output_reg, DP);
 		POSTING_READ(intel_dp->output_reg);
 	}
 
-	DP &= ~DP_AUDIO_OUTPUT_ENABLE;
-	I915_WRITE(intel_dp->output_reg, DP & ~DP_PORT_EN);
-	POSTING_READ(intel_dp->output_reg);
 	msleep(intel_dp->panel_power_down_delay);
 }