disp: msm: dp: skip mst display enable if payload is empty

During MST display enablement, the time slots for the display are
calculated during mst atomic check, which is then used in the
enable path. But if for some reason the payload wasn't allocated
successfully, then the enable path will have the time slots set to
0 which causes a send video timeout and also the missing payload
could result in null pointer dereferencing in step2 of mst payload
addition.

This change checks for this situation during pre-enable and returns
an error so the enable does not continue ahead.

Change-Id: If139707537b7a6dba169841ac82841851b4c09cb
Signed-off-by: Rajkumar Subbiah <[email protected]>

msm/dp/dp_mst_drm.c

@@ -600,7 +600,7 @@ static void _dp_mst_update_single_timeslot(struct dp_mst_private *mst,
 	}
 }
 
-static void _dp_mst_bridge_pre_enable_part1(struct dp_mst_bridge *dp_bridge)
+static int _dp_mst_bridge_pre_enable_part1(struct dp_mst_bridge *dp_bridge)
 {
 	struct dp_display *dp_display = dp_bridge->display;
 	struct sde_connector *c_conn =
@@ -613,6 +613,7 @@ static void _dp_mst_bridge_pre_enable_part1(struct dp_mst_bridge *dp_bridge)
 #endif
 	bool ret;
 	int pbn, slots;
+	int rc = 0;
 
 	DP_MST_DEBUG_V("enter\n");
 	SDE_EVT32_EXTERNAL(SDE_EVTLOG_FUNC_ENTRY, DP_MST_CONN_ID(dp_bridge));
@@ -623,7 +624,7 @@ static void _dp_mst_bridge_pre_enable_part1(struct dp_mst_bridge *dp_bridge)
 		drm_dp_send_power_updown_phy(&mst->mst_mgr, port, true);
 		dp_display->wakeup_phy_layer(dp_display, false);
 		_dp_mst_update_single_timeslot(mst, dp_bridge);
-		return;
+		return rc;
 	}
 
 	pbn = mst->mst_fw_cbs->calc_pbn_mode(&dp_bridge->dp_mode);
@@ -636,6 +637,11 @@ static void _dp_mst_bridge_pre_enable_part1(struct dp_mst_bridge *dp_bridge)
 #if (KERNEL_VERSION(6, 1, 0) <= LINUX_VERSION_CODE)
 	mst_state = to_drm_dp_mst_topology_state(mst->mst_mgr.base.state);
 	payload = drm_atomic_get_mst_payload_state(mst_state, port);
+	if (payload->time_slots <= 0) {
+		DP_ERR("time slots not allocated for conn:%d\n", DP_MST_CONN_ID(dp_bridge));
+		rc = -EINVAL;
+		goto end;
+	}
 
 	drm_dp_mst_update_slots(mst_state, DP_CAP_ANSI_8B10B);
 	mst->mst_fw_cbs->update_payload_part1(&mst->mst_mgr, mst_state, payload);
@@ -643,13 +649,17 @@ static void _dp_mst_bridge_pre_enable_part1(struct dp_mst_bridge *dp_bridge)
 	ret = mst->mst_fw_cbs->allocate_vcpi(&mst->mst_mgr, port, pbn, slots);
 	if (!ret) {
 		DP_ERR("mst: failed to allocate vcpi. bridge:%d\n", dp_bridge->id);
-		return;
+		rc = -EINVAL;
+		goto end;
 	}
 
 	dp_bridge->vcpi = port->vcpi.vcpi;
 	dp_bridge->pbn = pbn;
 #endif
 	_dp_mst_update_timeslots(mst, dp_bridge, port);
+
+end:
+	return rc;
 }
 
 static void _dp_mst_bridge_pre_enable_part2(struct dp_mst_bridge *dp_bridge)
@@ -793,7 +803,12 @@ static void dp_mst_bridge_pre_enable(struct drm_bridge *drm_bridge)
 		goto end;
 	}
 
-	_dp_mst_bridge_pre_enable_part1(bridge);
+	rc = _dp_mst_bridge_pre_enable_part1(bridge);
+	if (rc) {
+		DP_ERR("[%d] DP display pre-enable failed, rc=%d\n", bridge->id, rc);
+		dp->unprepare(dp, bridge->dp_panel);
+		goto end;
+	}
 
 	rc = dp->enable(dp, bridge->dp_panel);
 	if (rc) {