drm/i915/dp_mst: Work around Thunderbolt sink disconnect after SINK_COUNT_ESI read

[ Upstream commit 9cb15478 ]

Due to a problem in the iTBT DP-in adapter's firmware the sink on a TBT
link may get disconnected inadvertently if the SINK_COUNT_ESI and the
DP_LINK_SERVICE_IRQ_VECTOR_ESI0 registers are read in a single AUX
transaction. Work around the issue by reading these registers in
separate transactions.

The issue affects MTL+ platforms and will be fixed in the DP-in adapter
firmware, however releasing that firmware fix may take some time and is
not guaranteed to be available for all systems. Based on this apply the
workaround on affected platforms.

See HSD #13013007775.

v2: Cc'ing Mika Westerberg.

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13760
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14147


Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250519133417.1469181-1-imre.deak@intel.com


(cherry picked from commit c3a48363)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>