1 files changed, 49 insertions, 15 deletions

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index b7e3d8f44511..7d5883432085 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1778,27 +1778,38 @@ int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream,
 EXPORT_SYMBOL(snd_pcm_lib_ioctl);
 
 /**
- * snd_pcm_period_elapsed - update the pcm status for the next period
- * @substream: the pcm substream instance
+ * snd_pcm_period_elapsed_under_stream_lock() - update the status of runtime for the next period
+ *						under acquired lock of PCM substream.
+ * @substream: the instance of pcm substream.
+ *
+ * This function is called when the batch of audio data frames as the same size as the period of
+ * buffer is already processed in audio data transmission.
+ *
+ * The call of function updates the status of runtime with the latest position of audio data
+ * transmission, checks overrun and underrun over buffer, awaken user processes from waiting for
+ * available audio data frames, sampling audio timestamp, and performs stop or drain the PCM
+ * substream according to configured threshold.
+ *
+ * The function is intended to use for the case that PCM driver operates audio data frames under
+ * acquired lock of PCM substream; e.g. in callback of any operation of &snd_pcm_ops in process
+ * context. In any interrupt context, it's preferrable to use ``snd_pcm_period_elapsed()`` instead
+ * since lock of PCM substream should be acquired in advance.
  *
- * This function is called from the interrupt handler when the
- * PCM has processed the period size.  It will update the current
- * pointer, wake up sleepers, etc.
+ * Developer should pay enough attention that some callbacks in &snd_pcm_ops are done by the call of
+ * function:
  *
- * Even if more than one periods have elapsed since the last call, you
- * have to call this only once.
+ * - .pointer - to retrieve current position of audio data transmission by frame count or XRUN state.
+ * - .trigger - with SNDRV_PCM_TRIGGER_STOP at XRUN or DRAINING state.
+ * - .get_time_info - to retrieve audio time stamp if needed.
+ *
+ * Even if more than one periods have elapsed since the last call, you have to call this only once.
  */
-void snd_pcm_period_elapsed(struct snd_pcm_substream *substream)
+void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime;
-	unsigned long flags;
 
-	if (snd_BUG_ON(!substream))
-		return;
-
-	snd_pcm_stream_lock_irqsave(substream, flags);
 	if (PCM_RUNTIME_CHECK(substream))
-		goto _unlock;
+		return;
 	runtime = substream->runtime;
 
 	if (!snd_pcm_running(substream) ||
@@ -1811,7 +1822,30 @@ void snd_pcm_period_elapsed(struct snd_pcm_substream *substream)
 #endif
  _end:
 	kill_fasync(&runtime->fasync, SIGIO, POLL_IN);
- _unlock:
+}
+EXPORT_SYMBOL(snd_pcm_period_elapsed_under_stream_lock);
+
+/**
+ * snd_pcm_period_elapsed() - update the status of runtime for the next period by acquiring lock of
+ *			      PCM substream.
+ * @substream: the instance of PCM substream.
+ *
+ * This function is mostly similar to ``snd_pcm_period_elapsed_under_stream_lock()`` except for
+ * acquiring lock of PCM substream voluntarily.
+ *
+ * It's typically called by any type of IRQ handler when hardware IRQ occurs to notify event that
+ * the batch of audio data frames as the same size as the period of buffer is already processed in
+ * audio data transmission.
+ */
+void snd_pcm_period_elapsed(struct snd_pcm_substream *substream)
+{
+	unsigned long flags;
+
+	if (snd_BUG_ON(!substream))
+		return;
+
+	snd_pcm_stream_lock_irqsave(substream, flags);
+	snd_pcm_period_elapsed_under_stream_lock(substream);
 	snd_pcm_stream_unlock_irqrestore(substream, flags);
 }
 EXPORT_SYMBOL(snd_pcm_period_elapsed);