On Wed, 21 Aug 2024, Imre Deak <imre.deak@xxxxxxxxx> wrote: > On Wed, Aug 21, 2024 at 05:19:11PM +0300, Jani Nikula wrote: >> 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? > > The detect in this case will be retried with a 1 sec delay, since the > mode changes back to SST and the connector state stays disconnected. What exactly triggers the retry? I don't see this triggering the INTEL_HOTPLUG_RETRY case. I'm just trying to understand, please bear with me. BR, Jani. > >> 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 -- Jani Nikula, Intel
