disp: msm: dp: catch and propagate slot allocation failures

During atomic check for MST plugins, the driver is not catching and
propagating failures properly thereby incorrectly returning a
success even though the slot allocation had failed. This causes
invalid access of payload data in the MST topology manager.

This change checks the return code for slot allocation and atomic
check calls and propagates them to caller.

Change-Id: I383680c54feb826676965282e76bb3e5c3e17c4c
Signed-off-by: Rajkumar Subbiah <[email protected]>

msm/dp/dp_mst_drm.c

@@ -440,9 +440,9 @@ static int _dp_mst_compute_config(struct drm_atomic_state *state,
 {
 	int slots = 0, pbn;
 	struct sde_connector *c_conn = to_sde_connector(connector);
+	int rc = 0;
 #if (KERNEL_VERSION(6, 1, 0) <= LINUX_VERSION_CODE)
 	struct drm_dp_mst_topology_state *mst_state;
-	int rc;
 #endif
 
 	DP_MST_DEBUG_V("enter\n");
@@ -456,30 +456,37 @@ static int _dp_mst_compute_config(struct drm_atomic_state *state,
 	if (!mst_state->pbn_div)
 		mst_state->pbn_div = mst->dp_display->get_mst_pbn_div(mst->dp_display);
 
-	slots = mst->mst_fw_cbs->atomic_find_time_slots(state,
-			&mst->mst_mgr, c_conn->mst_port, pbn);
+	rc = mst->mst_fw_cbs->atomic_find_time_slots(state, &mst->mst_mgr, c_conn->mst_port, pbn);
+	if (rc < 0) {
+		DP_ERR("conn:%d failed to find vcpi slots. pbn:%d, rc:%d\n",
+				connector->base.id, pbn, rc);
+		goto end;
+	}
+
+	slots = rc;
 
 	rc = drm_dp_mst_atomic_check(state);
 	if (rc) {
-		DP_ERR("conn:%d mst atomic check failed\n", connector->base.id);
+		DP_ERR("conn:%d mst atomic check failed: rc=%d\n", connector->base.id, rc);
 		slots = 0;
+		goto end;
 	}
 #else
 	slots = mst->mst_fw_cbs->atomic_find_vcpi_slots(state,
 			&mst->mst_mgr, c_conn->mst_port, pbn, 0);
-#endif
 	if (slots < 0) {
 		DP_ERR("conn:%d failed to find vcpi slots. pbn:%d, slots:%d\n",
 				connector->base.id, pbn, slots);
-		return slots;
+		rc = slots;
+		slots = 0;
 	}
+#endif
 
-	DP_MST_DEBUG("conn:%d pbn:%d slots:%d\n", connector->base.id, pbn,
-			slots);
-	SDE_EVT32_EXTERNAL(SDE_EVTLOG_FUNC_EXIT, connector->base.id, pbn,
-			slots);
+end:
+	DP_MST_DEBUG("conn:%d pbn:%d slots:%d rc:%d\n", connector->base.id, pbn, slots, rc);
+	SDE_EVT32_EXTERNAL(SDE_EVTLOG_FUNC_EXIT, connector->base.id, pbn, slots, rc);
 
-	return slots;
+	return (rc < 0 ? rc : slots);
 }
 
 static void _dp_mst_update_timeslots(struct dp_mst_private *mst,
@@ -699,7 +706,6 @@ static void _dp_mst_bridge_pre_disable_part1(struct dp_mst_bridge *dp_bridge)
 #else
 	mst->mst_fw_cbs->reset_vcpi_slots(&mst->mst_mgr, port);
 #endif
-	pr_info("rsdbg: calling update after remove\n");
 	_dp_mst_update_timeslots(mst, dp_bridge, port);
 
 	DP_MST_DEBUG("mst bridge [%d] _pre disable part-1 complete\n",