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* [PATCH] drm/i915/dp_mst: Fix MST state after a sink reset
@ 2024-07-24 16:12 Imre Deak
  2024-07-24 16:21 ` Jani Nikula
                   ` (7 more replies)
  0 siblings, 8 replies; 18+ messages in thread
From: Imre Deak @ 2024-07-24 16:12 UTC (permalink / raw)
  To: intel-gfx

In some cases the sink can reset itself after it was configured into MST
mode, without the driver noticing the disconnected state. For instance
the reset may happen in the middle of a modeset, or the (long) HPD pulse
generated may be not long enough for the encoder detect handler to
observe the HPD's deasserted state. In this case the sink's DPCD
register programmed to enable MST will be reset, while the driver still
assumes MST is still enabled. Detect this condition, which will tear
down and recreate/re-enable the MST topology.

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11195
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c     |  3 +++
 drivers/gpu/drm/i915/display/intel_dp_mst.c | 30 +++++++++++++++++++++
 drivers/gpu/drm/i915/display/intel_dp_mst.h |  1 +
 3 files changed, 34 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 1e43e32e05199..c621f6daf8235 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -5878,6 +5878,9 @@ intel_dp_detect(struct drm_connector *connector,
 	else
 		status = connector_status_disconnected;
 
+	if (!intel_dp_mst_verify_dpcd_state(intel_dp))
+		status = connector_status_disconnected;
+
 	if (status == connector_status_disconnected) {
 		memset(&intel_dp->compliance, 0, sizeof(intel_dp->compliance));
 		memset(intel_connector->dp.dsc_dpcd, 0, sizeof(intel_connector->dp.dsc_dpcd));
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 27ce5c3f5951e..89b147e37b400 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -1998,3 +1998,33 @@ bool intel_dp_mst_crtc_needs_modeset(struct intel_atomic_state *state,
 
 	return false;
 }
+
+/**
+ * intel_dp_mst_verify_dpcd_state - verify the MST SW enabled state wrt. the DPCD
+ * @intel_dp: DP port object
+ *
+ * Verify if @intel_dp's MST enabled SW state matches the corresponding DPCD
+ * state. A long HPD pulse -not long enough to be detected as a disconnected
+ * state - could've reset the DPCD state, which requires tearing
+ * down/recreating the MST topology.
+ *
+ * Returns %true if the SW MST enabled and DPCD states match, %false
+ * otherwise.
+ */
+bool intel_dp_mst_verify_dpcd_state(struct intel_dp *intel_dp)
+{
+	int ret;
+	u8 val;
+
+	if (!intel_dp->is_mst)
+		return true;
+
+	ret = drm_dp_dpcd_readb(intel_dp->mst_mgr.aux, DP_MSTM_CTRL, &val);
+	if (ret < 0)
+		return false;
+
+	if (val != (DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC))
+		return false;
+
+	return true;
+}
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.h b/drivers/gpu/drm/i915/display/intel_dp_mst.h
index 8ca1d599091c6..9e4c7679f1c3a 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.h
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.h
@@ -27,5 +27,6 @@ int intel_dp_mst_atomic_check_link(struct intel_atomic_state *state,
 				   struct intel_link_bw_limits *limits);
 bool intel_dp_mst_crtc_needs_modeset(struct intel_atomic_state *state,
 				     struct intel_crtc *crtc);
+bool intel_dp_mst_verify_dpcd_state(struct intel_dp *intel_dp);
 
 #endif /* __INTEL_DP_MST_H__ */
-- 
2.44.2


^ permalink raw reply related	[flat|nested] 18+ messages in thread

end of thread, other threads:[~2024-08-26 13:33 UTC | newest]

Thread overview: 18+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2024-07-24 16:12 [PATCH] drm/i915/dp_mst: Fix MST state after a sink reset Imre Deak
2024-07-24 16:21 ` Jani Nikula
2024-07-24 16:40   ` Imre Deak
2024-08-22  9:38     ` Kandpal, Suraj
2024-08-23 13:03       ` Imre Deak
2024-07-24 16:49 ` ✗ Fi.CI.BAT: failure for " Patchwork
2024-08-07 13:44 ` ✗ Fi.CI.BUILD: failure for drm/i915/dp_mst: Fix MST state after a sink reset (rev2) Patchwork
2024-08-21 14:19 ` [PATCH] drm/i915/dp_mst: Fix MST state after a sink reset Jani Nikula
2024-08-21 14:25   ` Imre Deak
2024-08-22 10:00     ` Jani Nikula
2024-08-22 10:07       ` Imre Deak
2024-08-22 14:53         ` Jani Nikula
2024-08-23 13:09           ` Imre Deak
2024-08-23 16:29 ` [PATCH v2] " Imre Deak
2024-08-23 16:58 ` ✗ Fi.CI.CHECKPATCH: warning for drm/i915/dp_mst: Fix MST state after a sink reset (rev3) Patchwork
2024-08-23 17:06 ` ✓ Fi.CI.BAT: success " Patchwork
2024-08-24 17:23 ` ✗ Fi.CI.IGT: failure " Patchwork
2024-08-26 13:34   ` Imre Deak

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