1 files changed, 33 insertions, 8 deletions

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index bfd237c15e76..ae5f06895562 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -330,6 +330,13 @@ static bool drm_dp_sideband_msg_build(struct drm_dp_sideband_msg_rx *msg,
                         return false;
                 }
 
+                /*
+                 * ignore out-of-order messages or messages that are part of a
+                 * failed transaction
+                 */
+                if (!recv_hdr.somt && !msg->have_somt)
+                        return false;
+
                 /* get length contained in this portion */
                 msg->curchunk_len = recv_hdr.msg_len;
                 msg->curchunk_hdrlen = hdrlen;
@@ -2164,7 +2171,7 @@ out_unlock:
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume);
 
-static void drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
+static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
 {
         int len;
         u8 replyblock[32];
@@ -2179,12 +2186,12 @@ static void drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
                                replyblock, len);
         if (ret != len) {
                 DRM_DEBUG_KMS("failed to read DPCD down rep %d %d\n", len, ret);
-                return;
+                return false;
         }
         ret = drm_dp_sideband_msg_build(msg, replyblock, len, true);
         if (!ret) {
                 DRM_DEBUG_KMS("sideband msg build failed %d\n", replyblock[0]);
-                return;
+                return false;
         }
         replylen = msg->curchunk_len + msg->curchunk_hdrlen;
 
@@ -2196,21 +2203,32 @@ static void drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
                 ret = drm_dp_dpcd_read(mgr->aux, basereg + curreply,
                                     replyblock, len);
                 if (ret != len) {
-                        DRM_DEBUG_KMS("failed to read a chunk\n");
+                        DRM_DEBUG_KMS("failed to read a chunk (len %d, ret %d)\n",
+                                      len, ret);
+                        return false;
                 }
+
                 ret = drm_dp_sideband_msg_build(msg, replyblock, len, false);
-                if (ret == false)
+                if (!ret) {
                         DRM_DEBUG_KMS("failed to build sideband msg\n");
+                        return false;
+                }
+
                 curreply += len;
                 replylen -= len;
         }
+        return true;
 }
 
 static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr)
 {
         int ret = 0;
 
-        drm_dp_get_one_sb_msg(mgr, false);
+        if (!drm_dp_get_one_sb_msg(mgr, false)) {
+                memset(&mgr->down_rep_recv, 0,
+                       sizeof(struct drm_dp_sideband_msg_rx));
+                return 0;
+        }
 
         if (mgr->down_rep_recv.have_eomt) {
                 struct drm_dp_sideband_msg_tx *txmsg;
@@ -2266,7 +2284,12 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr)
 static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
 {
         int ret = 0;
-        drm_dp_get_one_sb_msg(mgr, true);
+
+        if (!drm_dp_get_one_sb_msg(mgr, true)) {
+                memset(&mgr->up_req_recv, 0,
+                       sizeof(struct drm_dp_sideband_msg_rx));
+                return 0;
+        }
 
         if (mgr->up_req_recv.have_eomt) {
                 struct drm_dp_sideband_msg_req_body msg;
@@ -2318,7 +2341,9 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
                         DRM_DEBUG_KMS("Got RSN: pn: %d avail_pbn %d\n", msg.u.resource_stat.port_number, msg.u.resource_stat.available_pbn);
                 }
 
-                drm_dp_put_mst_branch_device(mstb);
+                if (mstb)
+                        drm_dp_put_mst_branch_device(mstb);
+
                 memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
         }
         return ret;