ASoC: SOF: sof-audio: add support for setting up loopback routes

During route setup, playback stream routes are setup by going through
sink path, capture stream routes are set up by going through source path.
This is not sufficient to handle loopback cases between pipelines
configured with different directions, e.g. a sidetone or an amplifier
feedback connected to a speaker protection module. So, add the logic to
handle such routes between widgets that aren't in the list of DAPM widgets
associated with the same PCM.

Link: https://github.com/thesofproject/linux/issues/4042Suggested-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Chao Song <chao.song@linux.intel.com>
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20230313101302.20950-1-peter.ujfalusi@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/sof-audio.c

@@ -280,9 +280,11 @@ int sof_route_setup(struct snd_sof_dev *sdev, struct snd_soc_dapm_widget *wsourc
 static int sof_setup_pipeline_connections(struct snd_sof_dev *sdev,
 					  struct snd_soc_dapm_widget_list *list, int dir)
 {
+	const struct sof_ipc_tplg_ops *tplg_ops = sof_ipc_get_ops(sdev, tplg);
 	struct snd_soc_dapm_widget *widget;
+	struct snd_sof_route *sroute;
 	struct snd_soc_dapm_path *p;
-	int ret;
+	int ret = 0;
 	int i;
 
 	/*
@@ -325,6 +327,63 @@ static int sof_setup_pipeline_connections(struct snd_sof_dev *sdev,
 		}
 	}
 
+	/*
+	 * The above loop handles connections between widgets that belong to the DAPM widget list.
+	 * This is not sufficient to handle loopback cases between pipelines configured with
+	 * different directions, e.g. a sidetone or an amplifier feedback connected to a speaker
+	 * protection module.
+	 */
+	list_for_each_entry(sroute, &sdev->route_list, list) {
+		bool src_widget_in_dapm_list, sink_widget_in_dapm_list;
+		struct snd_sof_widget *swidget;
+
+		if (sroute->setup)
+			continue;
+
+		src_widget_in_dapm_list = widget_in_list(list, sroute->src_widget->widget);
+		sink_widget_in_dapm_list = widget_in_list(list, sroute->sink_widget->widget);
+
+		/*
+		 * if both source and sink are in the DAPM list, the route must already have been
+		 * set up above. And if neither are in the DAPM list, the route shouldn't be
+		 * handled now.
+		 */
+		if (src_widget_in_dapm_list == sink_widget_in_dapm_list)
+			continue;
+
+		/*
+		 * At this point either the source widget or the sink widget is in the DAPM list
+		 * with a route that might need to be set up. Check the use_count of the widget
+		 * that is not in the DAPM list to confirm if it is in use currently before setting
+		 * up the route.
+		 */
+		if (src_widget_in_dapm_list)
+			swidget = sroute->sink_widget;
+		else
+			swidget = sroute->src_widget;
+
+		mutex_lock(&swidget->setup_mutex);
+		if (!swidget->use_count) {
+			mutex_unlock(&swidget->setup_mutex);
+			continue;
+		}
+
+		if (tplg_ops && tplg_ops->route_setup) {
+			/*
+			 * this route will get freed when either the source widget or the sink
+			 * widget is freed during hw_free
+			 */
+			ret = tplg_ops->route_setup(sdev, sroute);
+			if (!ret)
+				sroute->setup = true;
+		}
+
+		mutex_unlock(&swidget->setup_mutex);
+
+		if (ret < 0)
+			return ret;
+	}
+
 	return 0;
 }