[Intel-gfx] [PATCH 3/4] drm/dp: Clarify clock recovery and channel equalization failures

[Dhinakaran Pandiyan]

The causes of clock recovery and channel equalization failures are not
explicitly printed in debug messages. Help debugging link training
failures by printing why it failed.

Doing this in the driver would mean re-implementing some of the drm static
functions that decode link status. Let's avoid that with these debug
messages in drm.

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 091053e..d763b57 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -64,12 +64,16 @@ bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
 
 	lane_align = dp_link_status(link_status,
 				    DP_LANE_ALIGN_STATUS_UPDATED);
-	if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0)
+	if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0) {
+		DRM_DEBUG_KMS("Inter-lane alignment not done\n");
 		return false;
+	}
 	for (lane = 0; lane < lane_count; lane++) {
 		lane_status = dp_get_lane_status(link_status, lane);
-		if ((lane_status & DP_CHANNEL_EQ_BITS) != DP_CHANNEL_EQ_BITS)
+		if ((lane_status & DP_CHANNEL_EQ_BITS) != DP_CHANNEL_EQ_BITS) {
+			DRM_DEBUG_KMS("Channel equalization not done for lane %d\n", lane);
 			return false;
+		}
 	}
 	return true;
 }
@@ -83,8 +87,10 @@ bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
 
 	for (lane = 0; lane < lane_count; lane++) {
 		lane_status = dp_get_lane_status(link_status, lane);
-		if ((lane_status & DP_LANE_CR_DONE) == 0)
+		if ((lane_status & DP_LANE_CR_DONE) == 0) {
+			DRM_DEBUG_KMS("Clock recovery not done for lane %d\n", lane);
 			return false;
+		}
 	}
 	return true;
 }
-- 
2.5.0