1 files changed, 77 insertions, 18 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index ea5d5ffd5522..2fa521812d23 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -469,6 +469,13 @@ static void link_disconnect_sink(struct dc_link *link)
         link->dpcd_sink_count = 0;
 }
 
+static void link_disconnect_remap(struct dc_sink *prev_sink, struct dc_link *link)
+{
+        dc_sink_release(link->local_sink);
+        link->local_sink = prev_sink;
+}
+
+
 static bool detect_dp(
         struct dc_link *link,
         struct display_sink_capability *sink_caps,
@@ -551,6 +558,17 @@ static bool detect_dp(
         return true;
 }
 
+static bool is_same_edid(struct dc_edid *old_edid, struct dc_edid *new_edid)
+{
+        if (old_edid->length != new_edid->length)
+                return false;
+
+        if (new_edid->length == 0)
+                return false;
+
+        return (memcmp(old_edid->raw_edid, new_edid->raw_edid, new_edid->length) == 0);
+}
+
 bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
 {
         struct dc_sink_init_data sink_init_data = { 0 };
@@ -558,9 +576,13 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
         uint8_t i;
         bool converter_disable_audio = false;
         struct audio_support *aud_support = &link->dc->res_pool->audio_support;
+        bool same_edid = false;
         enum dc_edid_status edid_status;
         struct dc_context *dc_ctx = link->ctx;
         struct dc_sink *sink = NULL;
+        struct dc_sink *prev_sink = NULL;
+        struct dpcd_caps prev_dpcd_caps;
+        bool same_dpcd = true;
         enum dc_connection_type new_connection_type = dc_connection_none;
         DC_LOGGER_INIT(link->ctx->logger);
         if (link->connector_signal == SIGNAL_TYPE_VIRTUAL)
@@ -575,6 +597,11 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
                         link->local_sink)
                 return true;
 
+        prev_sink = link->local_sink;
+        if (prev_sink != NULL) {
+                dc_sink_retain(prev_sink);
+                memcpy(&prev_dpcd_caps, &link->dpcd_caps, sizeof(struct dpcd_caps));
+        }
         link_disconnect_sink(link);
 
         if (new_connection_type != dc_connection_none) {
@@ -616,14 +643,25 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
                                 link,
                                 &sink_caps,
                                 &converter_disable_audio,
-                                aud_support, reason))
+                                aud_support, reason)) {
+                                if (prev_sink != NULL)
+                                        dc_sink_release(prev_sink);
                                 return false;
+                        }
 
+                        // Check if dpcp block is the same
+                        if (prev_sink != NULL) {
+                                if (memcmp(&link->dpcd_caps, &prev_dpcd_caps, sizeof(struct dpcd_caps)))
+                                        same_dpcd = false;
+                        }
                         /* Active dongle downstream unplug */
                         if (link->type == dc_connection_active_dongle
                                         && link->dpcd_caps.sink_count.
-                                        bits.SINK_COUNT == 0)
+                                        bits.SINK_COUNT == 0) {
+                                if (prev_sink != NULL)
+                                        dc_sink_release(prev_sink);
                                 return true;
+                        }
 
                         if (link->type == dc_connection_mst_branch) {
                                 LINK_INFO("link=%d, mst branch is now Connected\n",
@@ -634,6 +672,8 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
                                  * pbn_per_slot value leading to exception on dc_fixpt_div()
                                  */
                                 link->verified_link_cap = link->reported_link_cap;
+                                if (prev_sink != NULL)
+                                        dc_sink_release(prev_sink);
                                 return false;
                         }
 
@@ -643,6 +683,8 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
                 default:
                         DC_ERROR("Invalid connector type! signal:%d\n",
                                 link->connector_signal);
+                        if (prev_sink != NULL)
+                                dc_sink_release(prev_sink);
                         return false;
                 } /* switch() */
 
@@ -665,6 +707,8 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
                 sink = dc_sink_create(&sink_init_data);
                 if (!sink) {
                         DC_ERROR("Failed to create sink!\n");
+                        if (prev_sink != NULL)
+                                dc_sink_release(prev_sink);
                         return false;
                 }
 
@@ -688,22 +732,33 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
                         break;
                 }
 
-                if (link->connector_signal == SIGNAL_TYPE_DISPLAY_PORT &&
-                        sink_caps.transaction_type ==
-                        DDC_TRANSACTION_TYPE_I2C_OVER_AUX) {
-                        /*
-                         * TODO debug why Dell 2413 doesn't like
-                         *  two link trainings
-                         */
+                // Check if edid is the same
+                if ((prev_sink != NULL) && ((edid_status == EDID_THE_SAME) || (edid_status == EDID_OK)))
+                        same_edid = is_same_edid(&prev_sink->dc_edid, &sink->dc_edid);
 
-                        /* deal with non-mst cases */
-                        dp_hbr_verify_link_cap(link, &link->reported_link_cap);
-                }
+                // If both edid and dpcd are the same, then discard new sink and revert back to original sink
+                if ((same_edid) && (same_dpcd)) {
+                        link_disconnect_remap(prev_sink, link);
+                        sink = prev_sink;
+                        prev_sink = NULL;
+                } else {
+                        if (link->connector_signal == SIGNAL_TYPE_DISPLAY_PORT &&
+                                        sink_caps.transaction_type ==
+                                                DDC_TRANSACTION_TYPE_I2C_OVER_AUX) {
+                                /*
+                                 * TODO debug why Dell 2413 doesn't like
+                                 *  two link trainings
+                                 */
+
+                                /* deal with non-mst cases */
+                                dp_hbr_verify_link_cap(link, &link->reported_link_cap);
+                        }
 
-                /* HDMI-DVI Dongle */
-                if (sink->sink_signal == SIGNAL_TYPE_HDMI_TYPE_A &&
-                                !sink->edid_caps.edid_hdmi)
-                        sink->sink_signal = SIGNAL_TYPE_DVI_SINGLE_LINK;
+                        /* HDMI-DVI Dongle */
+                        if (sink->sink_signal == SIGNAL_TYPE_HDMI_TYPE_A &&
+                                        !sink->edid_caps.edid_hdmi)
+                                sink->sink_signal = SIGNAL_TYPE_DVI_SINGLE_LINK;
+                }
 
                 /* Connectivity log: detection */
                 for (i = 0; i < sink->dc_edid.length / EDID_BLOCK_SIZE; i++) {
@@ -762,10 +817,14 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
                 sink_caps.signal = SIGNAL_TYPE_NONE;
         }
 
-        LINK_INFO("link=%d, dc_sink_in=%p is now %s\n",
+        LINK_INFO("link=%d, dc_sink_in=%p is now %s prev_sink=%p dpcd same=%d edid same=%d\n",
                 link->link_index, sink,
                 (sink_caps.signal == SIGNAL_TYPE_NONE ?
-                        "Disconnected":"Connected"));
+                        "Disconnected":"Connected"), prev_sink,
+                        same_dpcd, same_edid);
+
+        if (prev_sink != NULL)
+                dc_sink_release(prev_sink);
 
         return true;
 }