From: Imre Deak <
[hidden email]>
BugLink:
https://bugs.launchpad.net/bugs/1910211
Signed-off-by: Imre Deak <
[hidden email]>
Reference:
https://gitlab.freedesktop.org/drm/intel/-/issues/2801#note_740352Signed-off-by: Koba Ko <
[hidden email]>
---
.../drm/i915/display/intel_dp_link_training.c | 36 ++++++++-----------
1 file changed, 15 insertions(+), 21 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 91d3979902d0..db4862760011 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -34,18 +34,6 @@ intel_dp_dump_link_status(const u8 link_status[DP_LINK_STATUS_SIZE])
link_status[3], link_status[4], link_status[5]);
}
-static int intel_dp_lttpr_count(struct intel_dp *intel_dp)
-{
- int count = drm_dp_lttpr_count(intel_dp->lttpr_common_caps);
-
- /*
- * Pretend no LTTPRs in case of LTTPR detection error, or
- * if too many (>8) LTTPRs are detected. This translates to link
- * training in transparent mode.
- */
- return count <= 0 ? 0 : count;
-}
-
static void intel_dp_reset_lttpr_count(struct intel_dp *intel_dp)
{
intel_dp->lttpr_common_caps[DP_PHY_REPEATER_CNT -
@@ -142,6 +130,17 @@ int intel_dp_lttpr_init(struct intel_dp *intel_dp)
return 0;
ret = intel_dp_read_lttpr_common_caps(intel_dp);
+ if (!ret)
+ return 0;
+
+ lttpr_count = drm_dp_lttpr_count(intel_dp->lttpr_common_caps);
+ /*
+ * Prevent setting LTTPR transparent mode explicitly if no LTTPRs are
+ * detected as this breaks link training at least on the Dell WD19TB
+ * dock.
+ */
+ if (lttpr_count == 0)
+ return 0;
/*
* See DP Standard v2.0 3.6.6.1. about the explicit disabling of
@@ -150,17 +149,12 @@ int intel_dp_lttpr_init(struct intel_dp *intel_dp)
*/
intel_dp_set_lttpr_transparent_mode(intel_dp, true);
- if (!ret)
- return 0;
-
- lttpr_count = intel_dp_lttpr_count(intel_dp);
-
/*
* In case of unsupported number of LTTPRs or failing to switch to
* non-transparent mode fall-back to transparent link training mode,
* still taking into account any LTTPR common lane- rate/count limits.
*/
- if (lttpr_count == 0)
+ if (lttpr_count < 0)
return 0;
if (!intel_dp_set_lttpr_transparent_mode(intel_dp, false)) {
@@ -222,11 +216,11 @@ intel_dp_phy_is_downstream_of_source(struct intel_dp *intel_dp,
enum drm_dp_phy dp_phy)
{
struct drm_i915_private *i915 = dp_to_i915(intel_dp);
- int lttpr_count = intel_dp_lttpr_count(intel_dp);
+ int lttpr_count = drm_dp_lttpr_count(intel_dp->lttpr_common_caps);
- drm_WARN_ON_ONCE(&i915->drm, lttpr_count == 0 && dp_phy != DP_PHY_DPRX);
+ drm_WARN_ON_ONCE(&i915->drm, lttpr_count <= 0 && dp_phy != DP_PHY_DPRX);
- return lttpr_count == 0 || dp_phy == DP_PHY_LTTPR(lttpr_count - 1);
+ return lttpr_count <= 0 || dp_phy == DP_PHY_LTTPR(lttpr_count - 1);
}
static u8 intel_dp_phy_voltage_max(struct intel_dp *intel_dp,
--
2.25.1
--
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