On Tue, Jun 14, 2022 at 03:32:59PM +0300, Jani Nikula wrote: > On Tue, 14 Jun 2022, Imre Deak <imre.deak@xxxxxxxxx> wrote: > > The WD22TB4 Thunderbolt dock at least will revert its DP_MAX_LINK_RATE > > from HBR3 to HBR2 after system suspend/resume if the DP_DP13_DPCD_REV > > registers are not read subsequently also as required. > > Does it actually change the behaviour depending on whether the dpcd is > read or not, or is this just about the resume path overwriting mgr->dpcd > with stuff from DP_DPCD_REV? Yes, the reading out DP_DP13_DPCD_REV has a side-effect, see https://gitlab.freedesktop.org/drm/intel/-/issues/5292#note_1343399 > drm_dp_mst_topology_mgr_set_mst() does use drm_dp_read_dpcd_caps() for > reading the caps, which would normally set mgr->dpcd from > DP_DP13_DPCD_REV. Right, but at that point DP_DP13_DPCD_REV returns HBR2 w/o this change. > BR, > Jani. > > > > > Fix this by reading DP_DP13_DPCD_REV registers as well, matching what is > > done during connector detection. While at it also fix up the same call > > in drm_dp_mst_dump_topology(). > > > > Cc: Lyude Paul <lyude@xxxxxxxxxx> > > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5292 > > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> > > --- > > drivers/gpu/drm/display/drm_dp_mst_topology.c | 7 ++----- > > 1 file changed, 2 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c > > index 67b3b9697da7f..18f2b6075b780 100644 > > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c > > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c > > @@ -3860,9 +3860,7 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr, > > if (!mgr->mst_primary) > > goto out_fail; > > > > - ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, > > - DP_RECEIVER_CAP_SIZE); > > - if (ret != DP_RECEIVER_CAP_SIZE) { > > + if (drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd) < 0) { > > drm_dbg_kms(mgr->dev, "dpcd read failed - undocked during suspend?\n"); > > goto out_fail; > > } > > @@ -4911,8 +4909,7 @@ void drm_dp_mst_dump_topology(struct seq_file *m, > > u8 buf[DP_PAYLOAD_TABLE_SIZE]; > > int ret; > > > > - ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, buf, DP_RECEIVER_CAP_SIZE); > > - if (ret) { > > + if (drm_dp_read_dpcd_caps(mgr->aux, buf) < 0) { > > seq_printf(m, "dpcd read failed\n"); > > goto out; > > } > > -- > Jani Nikula, Intel Open Source Graphics Center
