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

[Jani Nikula]

On Fri, 16 Dec 2022, Imre Deak <imre.deak at intel.com> wrote:
> 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.

Hmm, with the drm-misc *not* cherry-picking patches from drm-misc-next
to drm-misc-fixes, these will only get backported to stable kernels
after they hit Linus' tree in the next (as opposed to current) merge
window after a full development cycle. Wonder if they should be
expedited.

BR,
Jani.

>
>> 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
>> 

-- 
Jani Nikula, Intel Open Source Graphics Center