> -----Original Message----- > From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Imre > Deak > Sent: Wednesday, July 24, 2024 10:10 PM > To: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> > Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH] drm/i915/dp_mst: Fix MST state after a sink reset > > On Wed, Jul 24, 2024 at 07:21:53PM +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> Does this require a TODO to remind us to remove this when we decouple MST SST Sideband messaging? Otherwise LGTM, Reviewed-by: Suraj Kandpal <suraj.kandpal@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; > > > + > > > 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)) > > > > Hmm. This is not comparing the value to any software state, but some > > hardcoded combo of values which may or may not match. > > The software state is intel_dp->is_mst. That's atm the way to check if MST > was enabled previously and correspondingly DP_MSTM_CTRL programmed > to the above value. There is also intel_dp->mst_detect, but that can't be > used here, since that's reset after MST gets enabled. > > > In particular, this makes it harder to untangle MST from > > SST-with-sideband, I think. > > After that's enabled this should be changed; there isn't a good way atm to > tell full MST and SST-with-sideband apart. I don't see that as a problem as > only full MST will be enabled. > > > > > BR, > > Jani. > > > > > + 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
