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

[Ville Syrjälä]

On Mon, Feb 22, 2021 at 07:02:03PM +0200, Ville Syrjälä wrote:
> 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?

Just skip the RAD stuff by s/mstb->lct/hdr->lct/ here I guess?

-- 
Ville Syrjälä
Intel