[Intel-gfx] [PATCH v2 10/10] drm/i915: Leave FDI running after failed link training on LPT-H

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Currently we disable some parts of FDI setup after a failed link
training. But despite that we continue with the modeset as if everything
is fine. This results in tons of noise from the state checker, and
it means we're not following the proper modeset sequence for the rest of
crtc enabling, nor for crtc disabling.

Ideally we should abort the modeset and follow the proper disable
sequence to shut off everything we enabled so far, but that would
require a big rework of the modeset code. So instead just leave FDI
up and running in its untrained state, and log an error. This is
what we do on older platforms too.

v2: Fix a typo in the commit message

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/i915/intel_ddi.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 7f618cf5289c..5d20c64d8566 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -675,15 +675,16 @@ void hsw_fdi_link_train(struct drm_crtc *crtc)
 		temp = I915_READ(DP_TP_STATUS(PORT_E));
 		if (temp & DP_TP_STATUS_AUTOTRAIN_DONE) {
 			DRM_DEBUG_KMS("FDI link training done on step %d\n", i);
+			break;
+		}
 
-			/* Enable normal pixel sending for FDI */
-			I915_WRITE(DP_TP_CTL(PORT_E),
-				   DP_TP_CTL_FDI_AUTOTRAIN |
-				   DP_TP_CTL_LINK_TRAIN_NORMAL |
-				   DP_TP_CTL_ENHANCED_FRAME_ENABLE |
-				   DP_TP_CTL_ENABLE);
-
-			return;
+		/*
+		 * Leave things enabled even if we failed to train FDI.
+		 * Results in less fireworks from the state checker.
+		 */
+		if (i == ARRAY_SIZE(hsw_ddi_translations_fdi) * 2 - 1) {
+			DRM_ERROR("FDI link training failed!\n");
+			break;
 		}
 
 		temp = I915_READ(DDI_BUF_CTL(PORT_E));
@@ -712,7 +713,12 @@ void hsw_fdi_link_train(struct drm_crtc *crtc)
 		POSTING_READ(FDI_RX_MISC(PIPE_A));
 	}
 
-	DRM_ERROR("FDI link training failed!\n");
+	/* Enable normal pixel sending for FDI */
+	I915_WRITE(DP_TP_CTL(PORT_E),
+		   DP_TP_CTL_FDI_AUTOTRAIN |
+		   DP_TP_CTL_LINK_TRAIN_NORMAL |
+		   DP_TP_CTL_ENHANCED_FRAME_ENABLE |
+		   DP_TP_CTL_ENABLE);
 }
 
 void intel_ddi_init_dp_buf_reg(struct intel_encoder *encoder)
-- 
2.4.10