From: Wayne Lin <Wayne.Lin@xxxxxxx> commit 419e91ea3143bf26991442465ac64d9461e98d96 upstream. [Why & How] According to DP spec, broadcast message LCT equals to 1 and LCR equals to 6. Current implementation is incorrect. Fix it. In addition, revise a bit the hdr->rad handling to include broadcast case. Signed-off-by: Wayne Lin <Wayne.Lin@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx> Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20210224101521.6713-2-Wayne.Lin@xxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/drm_dp_mst_topology.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2829,10 +2829,15 @@ static int set_hdr_from_dst_qlock(struct else hdr->broadcast = 0; hdr->path_msg = txmsg->path_msg; - hdr->lct = mstb->lct; - hdr->lcr = mstb->lct - 1; - if (mstb->lct > 1) - memcpy(hdr->rad, mstb->rad, mstb->lct / 2); + if (hdr->broadcast) { + hdr->lct = 1; + hdr->lcr = 6; + } else { + hdr->lct = mstb->lct; + hdr->lcr = mstb->lct - 1; + } + + memcpy(hdr->rad, mstb->rad, hdr->lct / 2); return 0; }
