ASoC: SOF: sof-audio: Add support for hostless pipelines

This patch introduces the implementation of hostless pipelines in the SOF
driver by leveraging virtual widgets for DAPM. Hostless pipelines are used
in scenarios where audio data does not originate from or terminate at the
host, such as internal DSP processing pipelines or feedback loops.

The implementation includes:
- Support for virtual widgets in the topology to represent hostless pipelines.
  These virtual widgets are solely for the purpose of propagating the
  hw_params confirguation to the codec in the absence of a AIF component
- Virtual widgets are treated as checkpoints to stop propagating widget
  setup/free in the SOF driver. This patch updates the logic to the
  widget setup and free routines to handle virtual widgets and the rest of
  pipeline downstream from a virtual widget.

An example of a hostless pipeline in topology is:

Virtual input widget -> ToneGen -> mixin -> mixout -> gain -> DAI widget

This change enables the SOF driver to handle pipelines that are entirely
internal to the DSP, improving support for use cases like sidetone,
amplifier feedback, and other DSP-only processing scenarios.

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>

Author: ranj063

sound/soc/sof/sof-audio.c

@@ -13,6 +13,19 @@
 #include "sof-audio.h"
 #include "ops.h"
 
+/*
+ * Check is a DAI widget is an aggregated DAI. Aggregated DAI's have names ending in numbers
+ * starting with 0 and only the first DAI needs to be set up in the firmware. The rest of
+ * the aggregated DAI's are represented in the topology graph for completeness but do not
+ * need any firmware configuration.
+ */
+static bool is_aggregated_dai(struct snd_sof_widget *swidget)
+{
+	return (WIDGET_IS_DAI(swidget->id) &&
+	       isdigit(swidget->widget->name[strlen(swidget->widget->name) - 1]) &&
+	       swidget->widget->name[strlen(swidget->widget->name) - 1] != '0');
+}
+
 static bool is_virtual_widget(struct snd_sof_dev *sdev, struct snd_soc_dapm_widget *widget,
 			      const char *func)
 {
@@ -412,6 +425,10 @@ sof_unprepare_widgets_in_path(struct snd_sof_dev *sdev, struct snd_soc_dapm_widg
 	struct snd_soc_dapm_path *p;
 
 	if (is_virtual_widget(sdev, widget, __func__))
+		goto sink_unprepare;
+
+	/* skip aggregated DAIs */
+	if (!swidget || is_aggregated_dai(swidget))
 		return;
 
 	/* skip if the widget is in use or if it is already unprepared */
@@ -452,12 +469,16 @@ sof_prepare_widgets_in_path(struct snd_sof_dev *sdev, struct snd_soc_dapm_widget
 	int ret;
 
 	if (is_virtual_widget(sdev, widget, __func__))
-		return 0;
+		goto sink_prepare;
 
 	widget_ops = tplg_ops ? tplg_ops->widget : NULL;
 	if (!widget_ops)
 		return 0;
 
+	/* skip aggregated DAIs */
+	if (!swidget || is_aggregated_dai(swidget))
+		return 0;
+
 	if (!swidget || !widget_ops[widget->id].ipc_prepare || swidget->prepared)
 		goto sink_prepare;
 
@@ -506,18 +527,23 @@ static int sof_free_widgets_in_path(struct snd_sof_dev *sdev, struct snd_soc_dap
 {
 	struct snd_soc_dapm_widget_list *list = spcm->stream[dir].list;
 	struct snd_soc_dapm_path *p;
+	struct snd_sof_widget *swidget;
 	int err;
 	int ret = 0;
 
 	if (is_virtual_widget(sdev, widget, __func__))
-		return 0;
+		goto sink_free;
 
-	if (widget->dobj.private) {
-		err = sof_widget_free(sdev, widget->dobj.private);
-		if (err < 0)
-			ret = err;
-	}
+	swidget = widget->dobj.private;
 
+	/* skip aggregated DAIs */
+	if (!swidget || is_aggregated_dai(swidget))
+		return 0;
+
+	err = sof_widget_free(sdev, widget->dobj.private);
+	if (err < 0)
+		ret = err;
+sink_free:
 	/* free all widgets in the sink paths even in case of error to keep use counts balanced */
 	snd_soc_dapm_widget_for_each_sink_path(widget, p) {
 		if (!p->walking) {
@@ -552,11 +578,15 @@ static int sof_set_up_widgets_in_path(struct snd_sof_dev *sdev, struct snd_soc_d
 	int ret;
 
 	if (is_virtual_widget(sdev, widget, __func__))
-		return 0;
+		goto sink_setup;
 
 	if (swidget) {
 		int i;
 
+		/* skip aggregated DAIs */
+		if (!swidget || is_aggregated_dai(swidget))
+			return 0;
+
 		ret = sof_widget_setup(sdev, widget->dobj.private);
 		if (ret < 0)
 			return ret;
@@ -619,11 +649,10 @@ sof_walk_widgets_in_order(struct snd_sof_dev *sdev, struct snd_sof_pcm *spcm,
 		return 0;
 
 	for_each_dapm_widgets(list, i, widget) {
-		if (is_virtual_widget(sdev, widget, __func__))
-			continue;
 
-		/* starting widget for playback is AIF type */
-		if (dir == SNDRV_PCM_STREAM_PLAYBACK && widget->id != snd_soc_dapm_aif_in)
+		/* starting widget for playback is of AIF or snd_soc_dapm_input type */
+		if (dir == SNDRV_PCM_STREAM_PLAYBACK && (widget->id != snd_soc_dapm_aif_in &&
+		    widget->id != snd_soc_dapm_input))
 			continue;
 
 		/* starting widget for capture is DAI type */
@@ -904,29 +933,41 @@ struct snd_sof_widget *snd_sof_find_swidget(struct snd_soc_component *scomp,
 	return NULL;
 }
 
-/* find widget by stream name and direction */
-struct snd_sof_widget *
-snd_sof_find_swidget_sname(struct snd_soc_component *scomp,
-			   const char *pcm_name, int dir)
+static struct snd_sof_widget *snd_sof_find_swidget_sname_type(struct snd_soc_component *scomp,
+						  	      const char *sname,
+							      enum snd_soc_dapm_type type)
 {
 	struct snd_sof_dev *sdev = snd_soc_component_get_drvdata(scomp);
 	struct snd_sof_widget *swidget;
-	enum snd_soc_dapm_type type;
-
-	if (dir == SNDRV_PCM_STREAM_PLAYBACK)
-		type = snd_soc_dapm_aif_in;
-	else
-		type = snd_soc_dapm_aif_out;
 
 	list_for_each_entry(swidget, &sdev->widget_list, list) {
-		if (!strcmp(pcm_name, swidget->widget->sname) &&
-		    swidget->id == type)
+		if (!strcmp(sname, swidget->widget->sname) && swidget->id == type)
 			return swidget;
 	}
 
 	return NULL;
 }
 
+/* find widget by stream name and direction */
+struct snd_sof_widget *
+snd_sof_find_swidget_sname(struct snd_soc_component *scomp,
+			   const char *pcm_name, int dir)
+{
+	if (dir == SNDRV_PCM_STREAM_PLAYBACK) {
+		struct snd_sof_widget *swidget;
+
+		/* first look for an aif_in type widget */
+		swidget = snd_sof_find_swidget_sname_type(scomp, pcm_name, snd_soc_dapm_aif_in);
+		if (swidget)
+			return swidget;
+
+		/* if not found, look for an input type widget */
+		return snd_sof_find_swidget_sname_type(scomp, pcm_name, snd_soc_dapm_input);
+	}
+
+	return snd_sof_find_swidget_sname_type(scomp, pcm_name, snd_soc_dapm_aif_out);
+}
+
 struct snd_sof_dai *snd_sof_find_dai(struct snd_soc_component *scomp,
 				     const char *name)
 {