[PATCH 1/3] drm/display/dp_mst: Fix down/up message handling after sink disconnect

[Imre Deak]

On Wed, Dec 14, 2022 at 04:41:42PM -0500, Lyude Paul wrote:
> For the whole series:
> 
> Reviewed-by: Lyude Paul <lyude at redhat.com>

Thanks for the review, pushed it to drm-misc-next.

> Thanks!
> 
> On Wed, 2022-12-14 at 20:42 +0200, Imre Deak wrote:
> > If the sink gets disconnected during receiving a multi-packet DP MST AUX
> > down-reply/up-request sideband message, the state keeping track of which
> > packets have been received already is not reset. This results in a failed
> > sanity check for the subsequent message packet received after a sink is
> > reconnected (due to the pending message not yet completed with an
> > end-of-message-transfer packet), indicated by the
> > 
> > "sideband msg set header failed"
> > 
> > error.
> > 
> > Fix the above by resetting the up/down message reception state after a
> > disconnect event.
> > 
> > Cc: Lyude Paul <lyude at redhat.com>
> > Cc: <stable at vger.kernel.org> # v3.17+
> > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > ---
> >  drivers/gpu/drm/display/drm_dp_mst_topology.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > index 51a46689cda70..90819fff2c9ba 100644
> > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > @@ -3641,6 +3641,9 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
> >  		drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0);
> >  		ret = 0;
> >  		mgr->payload_id_table_cleared = false;
> > +
> > +		memset(&mgr->down_rep_recv, 0, sizeof(mgr->down_rep_recv));
> > +		memset(&mgr->up_req_recv, 0, sizeof(mgr->up_req_recv));
> >  	}
> >  
> >  out_unlock:
> 
> -- 
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
>