On Thu, 01 Oct 2026, FNU VISHWANATHA <[email protected]> wrote:
> After resume from warm boot/G3, immediately force a topology link address
> reprobe to ensure all MST ports are properly detected. This works around a
> race condition where some MST hubs incorrectly report port status bits before
> their internal state is fully initialized.
>
> By forcing the reprobe immediately after resume, combined with the fix in
> drm_dp_mst_handle_link_address_port() that detects input->output port
> transitions, we ensure that all displays are reliably detected even if the
> hub initially reports incorrect port status.
>
> Signed-off-by: FNU VISHWANATHA <[email protected]>
Is there a bug report about this with logs?
> ---
> drivers/gpu/drm/i915/display/intel_dp.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 3a67990411b3..fceda523efa3 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -7088,6 +7088,7 @@ void intel_dp_mst_resume(struct intel_display *display)
>
> for_each_intel_encoder(display->drm, encoder) {
> struct intel_dp *intel_dp;
> + struct drm_dp_mst_branch *mstb;
> int ret;
>
> if (encoder->type != INTEL_OUTPUT_DDI)
> @@ -7102,6 +7103,23 @@ void intel_dp_mst_resume(struct intel_display *display)
> if (ret) {
> intel_dp->is_mst = false;
> drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst.mgr,
> false);
> + continue;
> + }
> +
> + /* After resume, force a link address reprobe to ensure all
> ports
> + * are properly detected. This works around a race condition
> where
> + * some MST hubs incorrectly report port status bits during
> warm boot/G3.
> + * Ref: Sporadic second display not detected after warm
> boot/G3
> + */
> + if (intel_dp->is_mst) {
> + mutex_lock(&intel_dp->mst.mgr.lock);
> + mstb = intel_dp->mst.mgr.mst_primary;
> + if (mstb) {
> + drm_dp_mst_topology_get_mstb(mstb);
> + mstb->link_address_sent = false;
> + drm_dp_mst_topology_put_mstb(mstb);
> + }
> + mutex_unlock(&intel_dp->mst.mgr.lock);
> }
> }
> }
--
Jani Nikula, Intel
