Merge branch 'linus' into timers/core

To update with the latest fixes.

1 files changed, 40 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 27ce5c3f5951..17978a1f9ab0 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -1998,3 +1998,43 @@ 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)
+{
+	struct intel_display *display = to_intel_display(intel_dp);
+	struct intel_connector *connector = intel_dp->attached_connector;
+	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
+	struct intel_encoder *encoder = &dig_port->base;
+	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);
+
+	/* Adjust the expected register value for SST + SideBand. */
+	if (ret < 0 || val != (DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC)) {
+		drm_dbg_kms(display->drm,
+			    "[CONNECTOR:%d:%s][ENCODER:%d:%s] MST mode got reset, removing topology (ret=%d, ctrl=0x%02x)\n",
+			    connector->base.base.id, connector->base.name,
+			    encoder->base.base.id, encoder->base.name,
+			    ret, val);
+
+		return false;
+	}
+
+	return true;
+}