[PATCH v2] drm/i915/dp_mst: Work around Thunderbolt sink disconnect after SINK_COUNT_ESI read

[Mika Westerberg]

On Mon, May 19, 2025 at 04:34:17PM +0300, Imre Deak wrote:
> 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 at linux.intel.com>

Reviewed-by: Mika Westerberg <mika.westerberg at linux.intel.com>