drm/display/dp_mst: Add helper for finding payloads in atomic MST state

We already open-code this quite often, and will be iterating through
payloads even more once we've moved all of the payload tracking into the
atomic state. So, let's add a helper for doing this.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Wayne Lin <Wayne.Lin@amd.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Fangzhi Zuo <Jerry.Zuo@amd.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sean Paul <sean@poorly.run>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220817193847.557945-8-lyude@redhat.com

drivers/gpu/drm/display/drm_dp_mst_topology.c

@@ -1738,6 +1738,19 @@ drm_dp_mst_dump_port_topology_history(struct drm_dp_mst_port *port) {}
 #define save_port_topology_ref(port, type)
 #endif
 
+static struct drm_dp_mst_atomic_payload *
+drm_atomic_get_mst_payload_state(struct drm_dp_mst_topology_state *state,
+				 struct drm_dp_mst_port *port)
+{
+	struct drm_dp_mst_atomic_payload *payload;
+
+	list_for_each_entry(payload, &state->payloads, next)
+		if (payload->port == port)
+			return payload;
+
+	return NULL;
+}
+
 static void drm_dp_destroy_mst_branch_device(struct kref *kref)
 {
 	struct drm_dp_mst_branch *mstb =
@@ -4370,39 +4383,31 @@ int drm_dp_atomic_find_time_slots(struct drm_atomic_state *state,
 				  int pbn_div)
 {
 	struct drm_dp_mst_topology_state *topology_state;
-	struct drm_dp_mst_atomic_payload *pos, *payload = NULL;
-	int prev_slots, prev_bw, req_slots;
+	struct drm_dp_mst_atomic_payload *payload = NULL;
+	int prev_slots = 0, prev_bw = 0, req_slots;
 
 	topology_state = drm_atomic_get_mst_topology_state(state, mgr);
 	if (IS_ERR(topology_state))
 		return PTR_ERR(topology_state);
 
 	/* Find the current allocation for this port, if any */
-	list_for_each_entry(pos, &topology_state->payloads, next) {
-		if (pos->port == port) {
-			payload = pos;
-			prev_slots = payload->time_slots;
-			prev_bw = payload->pbn;
-
-			/*
-			 * This should never happen, unless the driver tries
-			 * releasing and allocating the same timeslot allocation,
-			 * which is an error
-			 */
-			if (WARN_ON(!prev_slots)) {
-				drm_err(mgr->dev,
-					"cannot allocate and release time slots on [MST PORT:%p] in the same state\n",
-					port);
-				return -EINVAL;
-			}
+	payload = drm_atomic_get_mst_payload_state(topology_state, port);
+	if (payload) {
+		prev_slots = payload->time_slots;
+		prev_bw = payload->pbn;
 
-			break;
+		/*
+		 * This should never happen, unless the driver tries
+		 * releasing and allocating the same timeslot allocation,
+		 * which is an error
+		 */
+		if (WARN_ON(!prev_slots)) {
+			drm_err(mgr->dev,
+				"cannot allocate and release time slots on [MST PORT:%p] in the same state\n",
+				port);
+			return -EINVAL;
 		}
 	}
-	if (!payload) {
-		prev_slots = 0;
-		prev_bw = 0;
-	}
 
 	if (pbn_div <= 0)
 		pbn_div = mgr->pbn_div;
@@ -4463,30 +4468,24 @@ int drm_dp_atomic_release_time_slots(struct drm_atomic_state *state,
 				     struct drm_dp_mst_port *port)
 {
 	struct drm_dp_mst_topology_state *topology_state;
-	struct drm_dp_mst_atomic_payload *pos;
-	bool found = false;
+	struct drm_dp_mst_atomic_payload *payload;
 
 	topology_state = drm_atomic_get_mst_topology_state(state, mgr);
 	if (IS_ERR(topology_state))
 		return PTR_ERR(topology_state);
 
-	list_for_each_entry(pos, &topology_state->payloads, next) {
-		if (pos->port == port) {
-			found = true;
-			break;
-		}
-	}
-	if (WARN_ON(!found)) {
+	payload = drm_atomic_get_mst_payload_state(topology_state, port);
+	if (WARN_ON(!payload)) {
 		drm_err(mgr->dev, "No payload for [MST PORT:%p] found in mst state %p\n",
 			port, &topology_state->base);
 		return -EINVAL;
 	}
 
-	drm_dbg_atomic(mgr->dev, "[MST PORT:%p] TU %d -> 0\n", port, pos->time_slots);
-	if (pos->time_slots) {
+	drm_dbg_atomic(mgr->dev, "[MST PORT:%p] TU %d -> 0\n", port, payload->time_slots);
+	if (payload->time_slots) {
 		drm_dp_mst_put_port_malloc(port);
-		pos->time_slots = 0;
-		pos->pbn = 0;
+		payload->time_slots = 0;
+		payload->pbn = 0;
 	}
 
 	return 0;
@@ -5182,18 +5181,8 @@ drm_dp_mst_atomic_check_port_bw_limit(struct drm_dp_mst_port *port,
 		return 0;
 
 	if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
-		bool found = false;
-
-		list_for_each_entry(payload, &state->payloads, next) {
-			if (payload->port != port)
-				continue;
-			if (!payload->pbn)
-				return 0;
-
-			found = true;
-			break;
-		}
-		if (!found)
+		payload = drm_atomic_get_mst_payload_state(state, port);
+		if (!payload)
 			return 0;
 
 		/*
@@ -5348,34 +5337,26 @@ int drm_dp_mst_atomic_enable_dsc(struct drm_atomic_state *state,
 				 bool enable)
 {
 	struct drm_dp_mst_topology_state *mst_state;
-	struct drm_dp_mst_atomic_payload *pos;
-	bool found = false;
+	struct drm_dp_mst_atomic_payload *payload;
 	int time_slots = 0;
 
 	mst_state = drm_atomic_get_mst_topology_state(state, port->mgr);
-
 	if (IS_ERR(mst_state))
 		return PTR_ERR(mst_state);
 
-	list_for_each_entry(pos, &mst_state->payloads, next) {
-		if (pos->port == port) {
-			found = true;
-			break;
-		}
-	}
-
-	if (!found) {
+	payload = drm_atomic_get_mst_payload_state(mst_state, port);
+	if (!payload) {
 		drm_dbg_atomic(state->dev,
 			       "[MST PORT:%p] Couldn't find payload in mst state %p\n",
 			       port, mst_state);
 		return -EINVAL;
 	}
 
-	if (pos->dsc_enabled == enable) {
+	if (payload->dsc_enabled == enable) {
 		drm_dbg_atomic(state->dev,
 			       "[MST PORT:%p] DSC flag is already set to %d, returning %d time slots\n",
-			       port, enable, pos->time_slots);
-		time_slots = pos->time_slots;
+			       port, enable, payload->time_slots);
+		time_slots = payload->time_slots;
 	}
 
 	if (enable) {
@@ -5387,7 +5368,7 @@ int drm_dp_mst_atomic_enable_dsc(struct drm_atomic_state *state,
 			return -EINVAL;
 	}
 
-	pos->dsc_enabled = enable;
+	payload->dsc_enabled = enable;
 
 	return time_slots;
 }