On Sun, 2016-12-04 at 19:31 -0600, Pierre-Louis Bossart wrote: > 100% reproducible issue found on SKL SkullCanyon NUC with two external > DP daisy-chained monitors in DP/MST mode. When turning off or changing > the input of the second monitor the machine stops with a kernel > oops. This issue happened with 4.8.8 as well as drm/drm-intel-nightly. > > This issue is traced to an inconsistent control flow in > drm_dp_update_payload_part1(): the 'port' pointer is set to NULL at > the same time as'req_payload.num_slots' is set to zero, but the pointer > is dereferenced even when req_payload.num_slot is zero. > > Fix by adding test condition to make sure both variables > are used consistently. This removes the kernel oops. > > There are still annoying cases where the primary display goes black > when the secondary display is turned off but it can be recovered from > by playing with the monitor inputs and power buttons. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98990 > Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx> > --- > drivers/gpu/drm/drm_dp_mst_topology.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c > index aa64448..5481fde 100644 > --- a/drivers/gpu/drm/drm_dp_mst_topology.c > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c > @@ -1815,7 +1815,7 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr) > drm_dp_create_payload_step1(mgr, mgr->proposed_vcpis[i]->vcpi, &req_payload); > mgr->payloads[i].num_slots = req_payload.num_slots; > mgr->payloads[i].vcpi = req_payload.vcpi; > - } else if (mgr->payloads[i].num_slots) { > + } else if (mgr->payloads[i].num_slots && port != NULL) { > mgr->payloads[i].num_slots = 0; > drm_dp_destroy_payload_step1(mgr, port, port->vcpi.vcpi, &mgr->payloads[i]); > req_payload.payload_state = mgr->payloads[i].payload_state; Or port shouldn't have been set to NULL in the first place. By adding, (port != NULL), you are not updating the payload state. -DK _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
