ALSA: firewire-lib: flush completed packets when reading PCM position

By flushing all completed but not yet reported packets before reading the PCM hardware position, the granularity of the pointer is improved from the interrupt interval to the packet size. Signed-off-by: Clemens Ladisch <[email protected]> Signed-off-by: Takashi Iwai <[email protected]>
berg · May 14, 2012 · e9148dd · e9148dd
1 parent 76fb878
commit e9148dd
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Showing 2 changed files with 15 additions and 12 deletions.
diff --git a/sound/firewire/amdtp.c b/sound/firewire/amdtp.c
@@ -531,6 +531,20 @@ int amdtp_out_stream_start(struct amdtp_out_stream *s, int channel, int speed)
 }
 EXPORT_SYMBOL(amdtp_out_stream_start);
 
+/**
+ * amdtp_out_stream_pcm_pointer - get the PCM buffer position
+ * @s: the AMDTP output stream that transports the PCM data
+ *
+ * Returns the current buffer position, in frames.
+ */
+unsigned long amdtp_out_stream_pcm_pointer(struct amdtp_out_stream *s)
+{
+	fw_iso_context_flush_completions(s->context);
+
+	return ACCESS_ONCE(s->pcm_buffer_pointer);
+}
+EXPORT_SYMBOL(amdtp_out_stream_pcm_pointer);
+
 /**
  * amdtp_out_stream_update - update the stream after a bus reset
  * @s: the AMDTP output stream

diff --git a/sound/firewire/amdtp.h b/sound/firewire/amdtp.h
@@ -84,6 +84,7 @@ void amdtp_out_stream_stop(struct amdtp_out_stream *s);
 void amdtp_out_stream_set_pcm_format(struct amdtp_out_stream *s,
 				     snd_pcm_format_t format);
 void amdtp_out_stream_pcm_prepare(struct amdtp_out_stream *s);
+unsigned long amdtp_out_stream_pcm_pointer(struct amdtp_out_stream *s);
 void amdtp_out_stream_pcm_abort(struct amdtp_out_stream *s);
 
 /**
@@ -140,18 +141,6 @@ static inline void amdtp_out_stream_pcm_trigger(struct amdtp_out_stream *s,
 	ACCESS_ONCE(s->pcm) = pcm;
 }
 
-/**
- * amdtp_out_stream_pcm_pointer - get the PCM buffer position
- * @s: the AMDTP output stream that transports the PCM data
- *
- * Returns the current buffer position, in frames.
- */
-static inline unsigned long
-amdtp_out_stream_pcm_pointer(struct amdtp_out_stream *s)
-{
-	return ACCESS_ONCE(s->pcm_buffer_pointer);
-}
-
 static inline bool cip_sfc_is_base_44100(enum cip_sfc sfc)
 {
 	return sfc & 1;