[PATCH 1/2] drm/dp_mst: Revise broadcast msg lct & lcr

[Wayne Lin]

[Why & How]
According to DP spec, broadcast message LCT equals to 1 and LCR equals
to 6. Current implementation is incorrect. Fix it.

Signed-off-by: Wayne Lin <Wayne.Lin at amd.com>
Cc: stable at vger.kernel.org
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 17dbed0a9800..713ef3b42054 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2727,8 +2727,14 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr,
 	else
 		hdr->broadcast = 0;
 	hdr->path_msg = txmsg->path_msg;
-	hdr->lct = mstb->lct;
-	hdr->lcr = mstb->lct - 1;
+	if (hdr->broadcast) {
+		hdr->lct = 1;
+		hdr->lcr = 6;
+	} else {
+		hdr->lct = mstb->lct;
+		hdr->lcr = mstb->lct - 1;
+	}
+
 	if (mstb->lct > 1)
 		memcpy(hdr->rad, mstb->rad, mstb->lct / 2);
 
-- 
2.17.1