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@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210531025103.17880-7-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>
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));
}
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;