On Wed, 2019-12-25 at 06:45 +0000, Lin, Wayne wrote: > > -----Original Message----- > > From: Lyude Paul <lyude@xxxxxxxxxx> > > Sent: Saturday, December 21, 2019 8:12 AM > > To: Lin, Wayne <Wayne.Lin@xxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx; > > amd-gfx@xxxxxxxxxxxxxxxxxxxxx > > Cc: Kazlauskas, Nicholas <Nicholas.Kazlauskas@xxxxxxx>; Wentland, Harry > > <Harry.Wentland@xxxxxxx>; Zuo, Jerry <Jerry.Zuo@xxxxxxx>; > > stable@xxxxxxxxxxxxxxx > > Subject: Re: [PATCH] drm/dp_mst: clear time slots for ports invalid > > > > Mhh-I think I understand the problem you're trying to solve here but I > > think this > > solution might be a bit overkill. When I did the rework of topology > > references > > for ports, I made it so that we can guarantee memory access to a port > > without > > it needing to be a valid part of the topology. As well, all parents of the > > port are > > guaranteed to be accessible for as long as the child is. Take a look at: > > > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2F01.org% > > 2Flinuxgraphics%2Fgfx-docs%2Fdrm%2Fgpu%2Fdrm-kms-helpers.html%23refco > > unt-relationships-in-a-topology&data=02%7C01%7Cwayne.lin%40amd.co > > m%7C722655b546c049dc081908d785aa6758%7C3dd8961fe4884e608e11a82d > > 994e183d%7C0%7C0%7C637124839257213115&sdata=Ctha3ja8kleeFOp > > PpA7EwDV1is81RAMsjqd1P6463ak%3D&reserved=0 > > > > It's also worth noting that because of this there's a lot of > > get_port_validated()/put_port_validated() calls in the MST helpers that > > are > > now bogus and need to be removed once I get a chance. For new code we > > should limit the use of topology references to sections of code where we > > need > > a guarantee that resources on the port/branch (such as a drm connector, dp > > aux port, etc.) won't go away for as long as we need to use them. > > > > Do you think we could change this patch so instead of removing it from the > > proposed payloads on the CONNECTION_STATUS_NOTIFY, we keep the port's > > memory allocation around until it's been removed from the proposed > > payloads > > table and clean it up there on the next payload update? > > > Really appreciate for your time and comments in detail. > > In this patch, I wanted to just set the proposed_vcpi->num_slots to 0 for > those > ports which are no longer in the topology due to there is no need to > allocate time > slots for these port. And expect those vcpi will be updated during next > update of > payload ID table by drm_dp_update_payload_part1(). > > I tried to use drm_dp_mst_topology_get_port_validated() as a helper to > decide whether a port is in the topology or not. Use this function to > iterate over > all ports that all proposed_vcpi[] drive to. If one port is not in the > topology, set the > num_slots of the proposed_vcpi for this port to 0. With num_slots as 0, > these > proposed_vcpi will be clean up in next payload table update by > drm_dp_update_payload_part1(). If a port is still in the topology, then > release > the reference count which was acquired previously from > drm_dp_mst_topology_get_port_validated() and do nothing. > > I didn't mean to kill invalid ports on receiving CONNECTION_STATUS_NOTIFY. > Sorry if I misuse or misunderstand something here? Ahh, it seems I made the mistake here then because from your explanation you're using the API exactly as intended :). All of this has me wondering if some day we should try to get rid of the payload tracking we have and move it into atomic. But, that's a problem for another day. Anyway-one small change below: > > > On Fri, 2019-12-06 at 16:39 +0800, Wayne Lin wrote: > > > [Why] > > > When change the connection status in a MST topology, mst device which > > > detect the event will send out CONNECTION_STATUS_NOTIFY messgae. > > > > > > e.g. src-mst-mst-sst => src-mst (unplug) mst-sst > > > > > > Currently, under the above case of unplugging device, ports which have > > > been allocated payloads and are no longer in the topology still occupy > > > time slots and recorded in proposed_vcpi[] of topology manager. > > > > > > If we don't clean up the proposed_vcpi[], when code flow goes to try > > > to update payload table by calling drm_dp_update_payload_part1(), we > > > will fail at checking port validation due to there are ports with > > > proposed time slots but no longer in the mst topology. As the result > > > of that, we will also stop updating the DPCD payload table of down > > > stream > > port. > > > [How] > > > While handling the CONNECTION_STATUS_NOTIFY message, add a detection > > > to see if the event indicates that a device is unplugged to an output > > > port. > > > If the detection is true, then iterrate over all proposed_vcpi[] to > > > see whether a port of the proposed_vcpi[] is still in the topology or > > > not. If the port is invalid, set its num_slots to 0. > > > > > > Thereafter, when try to update payload table by calling > > > drm_dp_update_payload_part1(), we can successfully update the DPCD > > > payload table of down stream port and clear the proposed_vcpi[] to NULL. > > > > > > Signed-off-by: Wayne Lin <Wayne.Lin@xxxxxxx> > > > Cc: stable@xxxxxxxxxxxxxxx > > > --- > > > drivers/gpu/drm/drm_dp_mst_topology.c | 24 > > +++++++++++++++++++++++- > > > 1 file changed, 23 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c > > > b/drivers/gpu/drm/drm_dp_mst_topology.c > > > index 5306c47dc820..2e236b6275c4 100644 > > > --- a/drivers/gpu/drm/drm_dp_mst_topology.c > > > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c > > > @@ -2318,7 +2318,7 @@ drm_dp_mst_handle_conn_stat(struct > > > drm_dp_mst_branch *mstb, { > > > struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; > > > struct drm_dp_mst_port *port; > > > - int old_ddps, ret; > > > + int old_ddps, old_input, ret, i; > > > u8 new_pdt; > > > bool dowork = false, create_connector = false; > > > > > > @@ -2349,6 +2349,7 @@ drm_dp_mst_handle_conn_stat(struct > > > drm_dp_mst_branch *mstb, > > > } > > > > > > old_ddps = port->ddps; > > > + old_input = port->input; > > > port->input = conn_stat->input_port; > > > port->mcs = conn_stat->message_capability_status; > > > port->ldps = conn_stat->legacy_device_plug_status; > > > @@ -2373,6 +2374,27 @@ drm_dp_mst_handle_conn_stat(struct > > > drm_dp_mst_branch *mstb, > > > dowork = false; > > > } > > > > > > + if (!old_input && old_ddps != port->ddps && !port->ddps) { > > > + for (i = 0; i < mgr->max_payloads; i++) { > > > + struct drm_dp_vcpi *vcpi = mgr->proposed_vcpis[i]; > > > + struct drm_dp_mst_port *port_validated; > > > + > > > + if (vcpi) { Let's invert this conditional to reduce the indenting here a bit if (!vcpi) continue; With that change this is: Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx> > > > + port_validated = > > > + container_of(vcpi, struct > > > drm_dp_mst_port, vcpi); > > > + port_validated = > > > + drm_dp_mst_topology_get_port_validated > > > (mgr, port_validated); > > > + if (!port_validated) { > > > + mutex_lock(&mgr->payload_lock); > > > + vcpi->num_slots = 0; > > > + mutex_unlock(&mgr->payload_lock); > > > + } else { > > > + drm_dp_mst_topology_put_port(port_vali > > > dated); > > > + } > > > + } > > > + } > > > + } > > > + > > > if (port->connector) > > > drm_modeset_unlock(&mgr->base.lock); > > > else if (create_connector) > > -- > > Cheers, > > Lyude Paul > -- > Best regards, > Wayne Lin -- Cheers, Lyude Paul _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
