On Wed, 24 Jul 2024, Imre Deak <imre.deak@xxxxxxxxx> wrote: > In some cases the sink can reset itself after it was configured into MST > mode, without the driver noticing the disconnected state. For instance > the reset may happen in the middle of a modeset, or the (long) HPD pulse > generated may be not long enough for the encoder detect handler to > observe the HPD's deasserted state. In this case the sink's DPCD > register programmed to enable MST will be reset, while the driver still > assumes MST is still enabled. Detect this condition, which will tear > down and recreate/re-enable the MST topology. > > Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11195 > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> > --- > drivers/gpu/drm/i915/display/intel_dp.c | 3 +++ > drivers/gpu/drm/i915/display/intel_dp_mst.c | 30 +++++++++++++++++++++ > drivers/gpu/drm/i915/display/intel_dp_mst.h | 1 + > 3 files changed, 34 insertions(+) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c > index 1e43e32e05199..c621f6daf8235 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp.c > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > @@ -5878,6 +5878,9 @@ intel_dp_detect(struct drm_connector *connector, > else > status = connector_status_disconnected; > > + if (!intel_dp_mst_verify_dpcd_state(intel_dp)) > + status = connector_status_disconnected; > + So I still don't understand. We've got a detect which we've determined is connected. But then we disconnect because the sink state has changed. How do we get another connect? BR, Jani. > if (status == connector_status_disconnected) { > memset(&intel_dp->compliance, 0, sizeof(intel_dp->compliance)); > memset(intel_connector->dp.dsc_dpcd, 0, sizeof(intel_connector->dp.dsc_dpcd)); > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c > index 27ce5c3f5951e..89b147e37b400 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c > @@ -1998,3 +1998,33 @@ bool intel_dp_mst_crtc_needs_modeset(struct intel_atomic_state *state, > > return false; > } > + > +/** > + * intel_dp_mst_verify_dpcd_state - verify the MST SW enabled state wrt. the DPCD > + * @intel_dp: DP port object > + * > + * Verify if @intel_dp's MST enabled SW state matches the corresponding DPCD > + * state. A long HPD pulse -not long enough to be detected as a disconnected > + * state - could've reset the DPCD state, which requires tearing > + * down/recreating the MST topology. > + * > + * Returns %true if the SW MST enabled and DPCD states match, %false > + * otherwise. > + */ > +bool intel_dp_mst_verify_dpcd_state(struct intel_dp *intel_dp) > +{ > + int ret; > + u8 val; > + > + if (!intel_dp->is_mst) > + return true; > + > + ret = drm_dp_dpcd_readb(intel_dp->mst_mgr.aux, DP_MSTM_CTRL, &val); > + if (ret < 0) > + return false; > + > + if (val != (DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC)) > + return false; > + > + return true; > +} > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.h b/drivers/gpu/drm/i915/display/intel_dp_mst.h > index 8ca1d599091c6..9e4c7679f1c3a 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.h > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.h > @@ -27,5 +27,6 @@ int intel_dp_mst_atomic_check_link(struct intel_atomic_state *state, > struct intel_link_bw_limits *limits); > bool intel_dp_mst_crtc_needs_modeset(struct intel_atomic_state *state, > struct intel_crtc *crtc); > +bool intel_dp_mst_verify_dpcd_state(struct intel_dp *intel_dp); > > #endif /* __INTEL_DP_MST_H__ */ -- Jani Nikula, Intel
