On Tue, 14 Jun 2022, Imre Deak <imre.deak@xxxxxxxxx> wrote: > 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 :o Okay, the commit message is fine as-is. > >> 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 -- Jani Nikula, Intel Open Source Graphics Center
