This commit takes ALSA fireface driver to perform sequence replay for media clock recovery. The protocol specific to RME Fireface series is not compliant to IEC 61883-1/6 since it has no CIP header, therefore presentation time is not used for media clock recovery. The sequence of the number of data blocks per packet is important. I note that the device skips an isochronous cycle corresponding to an empty packet or a NODATA packet in blocking transmission method of IEC 61883-1/6. For sequence replay, the cycle is handled as receiving an empty packet. Furthermore, it doesn't start packet transmission till receiving any packet. The sequence replay is tested with below models: * Fireface 400 * Fireface 800 * Fireface 802 I note that it is better to initialize Fireface 400 in advance by initialization transaction implemented in snd-fireface-ctl-service of snd-firewire-ctl-services project. You can see whether initialized or not by HOST LED on the device. Unless, the device often stops packet transmission even if session starts. I guess the sequence replay also works well with below models: * Fireface UFX * Fireface UCX Signed-off-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx> --- sound/firewire/fireface/amdtp-ff.c | 2 +- sound/firewire/fireface/ff-stream.c | 6 +++++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/sound/firewire/fireface/amdtp-ff.c b/sound/firewire/fireface/amdtp-ff.c index 119c0076b17a..98177b0666d3 100644 --- a/sound/firewire/fireface/amdtp-ff.c +++ b/sound/firewire/fireface/amdtp-ff.c @@ -168,6 +168,6 @@ int amdtp_ff_init(struct amdtp_stream *s, struct fw_unit *unit, else process_ctx_payloads = process_it_ctx_payloads; - return amdtp_stream_init(s, unit, dir, CIP_NO_HEADER, 0, + return amdtp_stream_init(s, unit, dir, CIP_BLOCKING | CIP_UNAWARE_SYT | CIP_NO_HEADER, 0, process_ctx_payloads, sizeof(struct amdtp_ff)); } diff --git a/sound/firewire/fireface/ff-stream.c b/sound/firewire/fireface/ff-stream.c index 97c356f2ac04..95bf405adb3d 100644 --- a/sound/firewire/fireface/ff-stream.c +++ b/sound/firewire/fireface/ff-stream.c @@ -199,7 +199,11 @@ int snd_ff_stream_start_duplex(struct snd_ff *ff, unsigned int rate) if (err < 0) goto error; - err = amdtp_domain_start(&ff->domain, 0, false, false); + // NOTE: The device doesn't transfer packets unless receiving any packet. The + // sequence of tx packets includes cycle skip corresponding to empty packet or + // NODATA packet in IEC 61883-1/6. The sequence of the number of data blocks per + // packet is important for media clock recovery. + err = amdtp_domain_start(&ff->domain, 0, true, true); if (err < 0) goto error; -- 2.27.0
