drm/i915/dp: Fetch downstream port info if needed during DPCD fetch

v2: Fix parenthesis mismatch, spotted by Jani Nikula

Tested-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
[danvet: Fixup merge conflict and MAX_DOWNSTREAM #define as spotted by
Jani.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 19 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