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* [PATCH V4] drm/dp_mst: Retrieve extended DPCD caps for topology manager
@ 2020-09-22  6:53 Koba Ko
  2020-09-22 18:01 ` Lyude Paul
  0 siblings, 1 reply; 4+ messages in thread
From: Koba Ko @ 2020-09-22  6:53 UTC (permalink / raw)
  To: Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann,
	David Airlie, Daniel Vetter, Lyude Paul, dri-devel, linux-kernel
  Cc: anthony.wong

As per DP-1.3, First check DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT.
If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 1,read the DP_DP13_DPCD_REV to
get the faster capability.
If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 0,read DP_DPCD_REV.

Signed-off-by: Koba Ko <koba.ko@canonical.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index e87542533640..63f8809b9aa4 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3686,9 +3686,9 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
 		WARN_ON(mgr->mst_primary);
 
 		/* get dpcd info */
-		ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, DP_RECEIVER_CAP_SIZE);
-		if (ret != DP_RECEIVER_CAP_SIZE) {
-			DRM_DEBUG_KMS("failed to read DPCD\n");
+		ret = drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd);
+		if (ret < 0) {
+			drm_dbg_kms(mgr->dev, "failed to read DPCD, ret %d\n", ret);
 			goto out_unlock;
 		}
 
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2020-09-23 14:18 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2020-09-22  6:53 [PATCH V4] drm/dp_mst: Retrieve extended DPCD caps for topology manager Koba Ko
2020-09-22 18:01 ` Lyude Paul
2020-09-23  2:16   ` Koba Ko
2020-09-23 14:17     ` Lyude Paul

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