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ALSA: fireface: perform sequence replay for media clock recovery

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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>
This commit is contained in:
Takashi Sakamoto 2021-05-31 11:51:03 +09:00 committed by Takashi Iwai
parent a9dd8a61b6
commit dfacca3986
2 changed files with 6 additions and 2 deletions
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2
sound/firewire/fireface/amdtp-ff.c
View File

@ -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));
}

6
sound/firewire/fireface/ff-stream.c
View File

@ -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;