ASoC: SOF: ipc4-pcm: Implement pipeline trigger reference counting

Use the started_count and paused_count to implement reference counting
when making decisions to start/stop/pause pipelines during the FE DAI
trigger. This is necessary to trigger the shared pipelines in the FE DAI
trigger properly.

With IPC4, the FE trigger will issue multiple pipeline state changes,
and the triggers are propagated downstream to connected pipelines by
the SOF driver - not the firmware. This creates a window for race
conditions where an FE trigger preempts another one, which results
in inconsistent pipeline states and refcounts.

This patch introduces a mutex lock for the pcm trigger that guarantees
that IPC4 state and resources are accessed in a serialized manner.
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20230127120031.10709-15-peter.ujfalusi@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/ipc4-priv.h

@@ -70,6 +70,7 @@ struct sof_ipc4_fw_library {
  *		    base firmware
  *
  * @load_library: Callback function for platform dependent library loading
+ * @trigger_mutex: Mutex to protect pipeline triggers, ref counts and states
  */
 struct sof_ipc4_fw_data {
 	u32 manifest_fw_hdr_offset;
@@ -82,6 +83,7 @@ struct sof_ipc4_fw_data {
 
 	int (*load_library)(struct snd_sof_dev *sdev,
 			    struct sof_ipc4_fw_library *fw_lib, bool reload);
+	struct mutex trigger_mutex; /* protect pipeline triggers, ref counts and states */
 };
 
 extern const struct sof_ipc_fw_loader_ops ipc4_loader_ops;

sound/soc/sof/ipc4.c

@@ -662,6 +662,8 @@ static int sof_ipc4_init(struct snd_sof_dev *sdev)
 {
 	struct sof_ipc4_fw_data *ipc4_data = sdev->private;
 
+	mutex_init(&ipc4_data->trigger_mutex);
+
 	xa_init_flags(&ipc4_data->fw_lib_xa, XA_FLAGS_ALLOC);
 
 	return 0;