linux-kernel - [PATCH] Revert "drm/dp_mst: Retrieve extended DPCD caps for topology manager"

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Date:   Tue,  3 Nov 2020 11:49:07 +0800
From:   Koba Ko <koba.ko@...onical.com>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Lyude Paul <lyude@...hat.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH] Revert "drm/dp_mst: Retrieve extended DPCD caps for topology manager"

This reverts commit ad44c03208e46b83e4ae3269e32c9e524aa71cf8.

Currently DRM driver assume the source device caps is higher than the MST device
caps. With this commit, this statement would be broken.

e.g. the source device only support DP1.2 and the mst device support DP1.4.

Signed-off-by: Koba Ko <koba.ko@...onical.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 153b6065ba29..e87542533640 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3686,10 +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_read_dpcd_caps(mgr->aux, mgr->dpcd);
-		if (ret < 0) {
-			drm_dbg_kms(mgr->dev, "%s: failed to read DPCD, ret %d\n",
-				    mgr->aux->name, ret);
+		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");
 			goto out_unlock;
 		}
 
-- 
2.17.1