drm/i915/dp_mst: Fix configuring TUs for a disconnected stream

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During an atomic commit after all the MST stream CRTC state is computed
the driver ensures that the sum of TUs of all the streams on a given MST
topology link is within limits (63 for 8b10 and 64 for 128b132b). For a
disconnected stream the DRM MST core's BW verification doesn't ensure
this, because the topology state it uses for this is destroyed as soon
as the stream (i.e. MST connector/port) is disconnected. The driver
should keep the link state valid even for such disconnected streams, as
userspace may disable them one-by-one only in a deferred way. Ensure the
link's sum of TUs stays within limits in this case by simply reusing the
maximum link BPP limit from the stream's (i.e. CRTC's) old state.

The disconnection can happen either via the whole topology getting
disconnected or via only the given stream's port getting disconnected.
Check for both of these conditions separately, as a connector gets
unregistered after a link disconnect event only in a deferred way.

Cc: stable@vger.kernel.org # v6.10+
Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/16073
Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/16384
Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260907174413.741851-2-imre.deak@intel.com

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This commit is contained in:

Imre Deak 2026-09-07 20:44:13 +03:00

parent 270681fbff

commit ee00f8fbb2

3 changed files with 25 additions and 1 deletions

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21

drivers/gpu/drm/i915/display/intel_dp_mst.c

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2

drivers/gpu/drm/i915/display/intel_dp_mst.h

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3

drivers/gpu/drm/i915/display/intel_link_bw.c

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