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

[Ville Syrjälä]

On Mon, Feb 22, 2021 at 12:00:26PM +0800, Wayne Lin wrote:
> [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);

We should also do something about RAD no?

>  
> -- 
> 2.17.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Ville Syrjälä
Intel