drm/i915/mst: Disable transcoder before deleting the payload

Bspec tells us that we should disable the transcoder before
deleting the payload. Looks like this has been reversed since
MST support was added.

I suppose this shouldn't matter in practice since the downstream
device shouldn't really do anything with the new payload until
we send the ACT. But I see no compelling reason to deviate from
the bspec sequence regardless.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231018154123.5479-3-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

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

@@ -587,10 +587,6 @@ static void intel_mst_disable_dp(struct intel_atomic_state *state,
 	struct intel_dp *intel_dp = &dig_port->dp;
 	struct intel_connector *connector =
 		to_intel_connector(old_conn_state->connector);
-	struct drm_dp_mst_topology_state *new_mst_state =
-		drm_atomic_get_new_mst_topology_state(&state->base, &intel_dp->mst_mgr);
-	struct drm_dp_mst_atomic_payload *new_payload =
-		drm_atomic_get_mst_payload_state(new_mst_state, connector->port);
 	struct drm_i915_private *i915 = to_i915(connector->base.dev);
 
 	drm_dbg_kms(&i915->drm, "active links %d\n",
@@ -598,8 +594,6 @@ static void intel_mst_disable_dp(struct intel_atomic_state *state,
 
 	intel_hdcp_disable(intel_mst->connector);
 
-	drm_dp_remove_payload_part1(&intel_dp->mst_mgr, new_mst_state, new_payload);
-
 	intel_audio_codec_disable(encoder, old_crtc_state, old_conn_state);
 }
 
@@ -634,6 +628,8 @@ static void intel_mst_post_disable_dp(struct intel_atomic_state *state,
 
 	intel_disable_transcoder(old_crtc_state);
 
+	drm_dp_remove_payload_part1(&intel_dp->mst_mgr, new_mst_state, new_payload);
+
 	clear_act_sent(encoder, old_crtc_state);
 
 	intel_de_rmw(dev_priv, TRANS_DDI_FUNC_CTL(old_crtc_state->cpu_transcoder),