> -----Original Message----- > From: Intel-gfx <[email protected]> On Behalf Of Imre > Deak > Sent: Monday, September 7, 2026 11:14 PM > To: [email protected]; [email protected] > Cc: [email protected] > Subject: [PATCH 1/2] drm/i915/dp_mst: Fix configuring FEC for a disconnected > stream > > During an atomic commit after all the MST stream CRTC state is computed the > driver ensures that the FEC is configured the same way (enabled or > disabled) for all the streams on a given MST topology's link. > drm_dp_mst_port_downstream_of_parent() used to determine if a stream is > downstream of an MST port will return false if the whole topology is > disconnected, since in that case it can't verify that the port/ parent_port > passed > to it is in the given MST topology. This is a problem during the above FEC > configuration check, since > intel_dp_mst_check_dsc_change()->get_pipes_downstream_of_mst_ports() > will not return all the stream CRTCs/pipes for the topology as expected. > Since passing parent_port==NULL to get_pipes_downstream_of_mst_port() > is meant to return all the streams for the given topology (i.e. mst_mgr) skip > checking if an MST port is downstream of a parent port in this case. > I already have a fix for this posted long back. https://patchwork.freedesktop.org/series/168570/
Thanks and Regards, Arun R Murthy -------------------- > This fixes a problem where the FEC configuration check explained above failed > to ensure that all streams' FEC is configured the same way if the topology was > disconnected, leading to a FEC state mismatch error. > > Cc: [email protected] # v6.10+ > Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/16073 > Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/16384 > Signed-off-by: Imre Deak <[email protected]> > --- > drivers/gpu/drm/i915/display/intel_dp_mst.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c > b/drivers/gpu/drm/i915/display/intel_dp_mst.c > index 6a869d0f6ffc0..20766b6c0bcfa 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c > @@ -856,7 +856,8 @@ static u8 get_pipes_downstream_of_mst_port(struct > intel_atomic_state *state, > if (&connector->mst.dp->mst.mgr != mst_mgr) > continue; > > - if (connector->mst.port != parent_port && > + if (parent_port && > + connector->mst.port != parent_port && > !drm_dp_mst_port_downstream_of_parent(mst_mgr, > connector->mst.port, > parent_port)) > -- > 2.49.1
