[PATCH] drm/dp: Power cycle display if LINK_ADDRESS fails.

Dhinakaran Pandiyan dhinakaran.pandiyan at intel.com
Thu Dec 21 06:36:24 UTC 2017

Occasionally there are LINK_ADDRESS sideband messages timing out with the
Lenovo MST dock + Dell MST monitor(w/ in-built branch) setup I have. These
failures lead to the display not coming up on boot. Power cycling the port
corresponding to the MST monitor's branch device and resending the message
fixes the issue. I am not entirely sure if this is specific to my setup.
However, as the power state is toggled conditionally on LINK_ADDRESS
timeouts, this should not affect the working cases.

Cc: Lyude <lyude at redhat.com>
Cc: Dave Airlie <airlied at redhat.com>
Cc: Jani Nikula <jani.nikula at intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
 drivers/gpu/drm/drm_dp_mst_topology.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 70dcfa58d3c2..e06defcdcf18 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1596,8 +1596,9 @@ static void drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 	int len;
 	struct drm_dp_sideband_msg_tx *txmsg;
 	int ret;
+	int attempts = 5;
-	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
+retry:	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
 	if (!txmsg)
@@ -1635,9 +1636,17 @@ static void drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
+	} else if (attempts--) {
+		kfree(txmsg);
+		drm_dp_send_power_updown_phy(mstb->mgr, mstb->port_parent,
+					     false);
+		drm_dp_send_power_updown_phy(mstb->mgr, mstb->port_parent,
+					     true);
+		DRM_DEBUG_KMS("link address failed %d, retrying\n", ret);
+		goto retry;
 	} else {
 		mstb->link_address_sent = false;
-		DRM_DEBUG_KMS("link address failed %d\n", ret);
+		DRM_DEBUG_KMS("link address failed %d, giving up\n", ret);

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