2 files changed, 21 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 1474f84fdbd0..42bdca47c5d6 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -37,6 +37,7 @@
 #include "i915_drm.h"
 #include "i915_drv.h"
 
+#define DP_RECEIVER_CAP_SIZE    0xf
 #define DP_LINK_STATUS_SIZE     6
 #define DP_LINK_CHECK_TIMEOUT   (10 * 1000)
 
@@ -1964,12 +1965,25 @@ static bool
 intel_dp_get_dpcd(struct intel_dp *intel_dp)
 {
         if (intel_dp_aux_native_read_retry(intel_dp, 0x000, intel_dp->dpcd,
-                                           sizeof(intel_dp->dpcd)) &&
-            (intel_dp->dpcd[DP_DPCD_REV] != 0)) {
-                return true;
-        }
+                                           sizeof(intel_dp->dpcd)) == 0)
+                return false; /* aux transfer failed */
 
-        return false;
+        if (intel_dp->dpcd[DP_DPCD_REV] == 0)
+                return false; /* DPCD not present */
+
+        if (!(intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] &
+              DP_DWN_STRM_PORT_PRESENT))
+                return true; /* native DP sink */
+
+        if (intel_dp->dpcd[DP_DPCD_REV] == 0x10)
+                return true; /* no per-port downstream info */
+
+        if (intel_dp_aux_native_read_retry(intel_dp, DP_DOWNSTREAM_PORT_0,
+                                           intel_dp->downstream_ports,
+                                           DP_MAX_DOWNSTREAM_PORTS) == 0)
+                return false; /* downstream port status fetch failed */
+
+        return true;
 }
 
 static void
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 351fd7179cd7..79f8ed66574e 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -332,6 +332,7 @@ struct intel_hdmi {
 };
 
 #define DP_RECEIVER_CAP_SIZE            0xf
+#define DP_MAX_DOWNSTREAM_PORTS         0x10
 #define DP_LINK_CONFIGURATION_SIZE      9
 
 struct intel_dp {
@@ -346,6 +347,7 @@ struct intel_dp {
         uint8_t link_bw;
         uint8_t lane_count;
         uint8_t dpcd[DP_RECEIVER_CAP_SIZE];
+        uint8_t downstream_ports[DP_MAX_DOWNSTREAM_PORTS];
         struct i2c_adapter adapter;
         struct i2c_algo_dp_aux_data algo;
         bool is_pch_edp;