ALSA: firewire-lib: Add support for duplex streams synchronization in blocking mode

Generally, the devices can synchronize to handle 'presentation timestamp'
in CIP packets. This commit adds functionality to pick up this timestamp from
in-packets transmitted by the device, then use it for out packets.

In current implementation, this module generated the timestamp by itself. This
is 'SYT Match' mode. Then drivers with this module acts as synchronization
master. This commit allows this module to act as synchronization slave.

This commit restricts this mechanism is only available in blocking mode because
handling the timestamp in non-blocking mode is more complicated than in
blocking mode.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 42 insertions, 3 deletions

diff --git a/sound/firewire/amdtp.h b/sound/firewire/amdtp.h
index 098187d4b499..2bd3b27ac938 100644
--- a/sound/firewire/amdtp.h
+++ b/sound/firewire/amdtp.h
@@ -20,11 +20,14 @@
  *	at half the actual sample rate with twice the number of channels;
  *	two samples of a channel are stored consecutively in the packet.
  *	Requires blocking mode and SYT_INTERVAL-aligned PCM buffer size.
+ * @CIP_SYNC_TO_DEVICE: In sync to device mode, time stamp in out packets is
+ *	generated by in packets. Defaultly this driver generates timestamp.
  */
 enum cip_flags {
-	CIP_NONBLOCKING	= 0x00,
-	CIP_BLOCKING	= 0x01,
-	CIP_HI_DUALWIRE	= 0x02,
+	CIP_NONBLOCKING		= 0x00,
+	CIP_BLOCKING		= 0x01,
+	CIP_HI_DUALWIRE		= 0x02,
+	CIP_SYNC_TO_DEVICE	= 0x04,
 };
 
 /**
@@ -104,6 +107,10 @@ struct amdtp_stream {
 	bool pointer_flush;
 
 	struct snd_rawmidi_substream *midi[AMDTP_MAX_CHANNELS_FOR_MIDI * 8];
+
+	bool callbacked;
+	wait_queue_head_t callback_wait;
+	struct amdtp_stream *sync_slave;
 };
 
 int amdtp_stream_init(struct amdtp_stream *s, struct fw_unit *unit,
@@ -201,4 +208,36 @@ static inline bool cip_sfc_is_base_44100(enum cip_sfc sfc)
 	return sfc & 1;
 }
 
+static inline void amdtp_stream_set_sync(enum cip_flags sync_mode,
+					 struct amdtp_stream *master,
+					 struct amdtp_stream *slave)
+{
+	if (sync_mode == CIP_SYNC_TO_DEVICE) {
+		master->flags |= CIP_SYNC_TO_DEVICE;
+		slave->flags |= CIP_SYNC_TO_DEVICE;
+		master->sync_slave = slave;
+	} else {
+		master->flags &= ~CIP_SYNC_TO_DEVICE;
+		slave->flags &= ~CIP_SYNC_TO_DEVICE;
+		master->sync_slave = NULL;
+	}
+
+	slave->sync_slave = NULL;
+}
+
+/**
+ * amdtp_stream_wait_callback - sleep till callbacked or timeout
+ * @s: the AMDTP stream
+ * @timeout: msec till timeout
+ *
+ * If this function return false, the AMDTP stream should be stopped.
+ */
+static inline bool amdtp_stream_wait_callback(struct amdtp_stream *s,
+					      unsigned int timeout)
+{
+	return wait_event_timeout(s->callback_wait,
+				  s->callbacked == true,
+				  msecs_to_jiffies(timeout)) > 0;
+}
+
 #endif