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author | Takashi Sakamoto <o-takashi@sakamocchi.jp> | 2014-04-25 22:44:52 +0900 |
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committer | Takashi Iwai <tiwai@suse.de> | 2014-05-26 14:21:46 +0200 |
commit | 7b2d99fa6b127707cf0d78feedbb3613aed4d576 (patch) | |
tree | 5dbee1997b68e276446643ac1f7885928337cf3d /sound/firewire/amdtp.c | |
parent | 10550bea44a8d7cec8a503c8f91fb6014e7849e9 (diff) | |
download | op-kernel-dev-7b2d99fa6b127707cf0d78feedbb3613aed4d576.zip op-kernel-dev-7b2d99fa6b127707cf0d78feedbb3613aed4d576.tar.gz |
ALSA: firewire-lib/dice/speakers: Add common PCM constraints for AMDTP streams
This commit adds common PCM constraints according to current firewire-lib
implementation.
1.Maximum width for each sample is limited by 24.
AM824 in IEC 61883-6 can deliver 24bit data.
2. Minimum time for period is 5msec.
Apply the old value. For shorter latency, further works are needed.
3. In blocking mode, frames per period/buffer is aligned to 32.
Each packet can include some frames depending on its sampling rate. In
blocking mode, the number equals to SYT_INTERVAL. Currently firewire-lib
can schedule snd_pcm_period_elapsed() for each packet. So, for accurate
PCM interrupt, the number of frames per period/buffer should be aligned
to SYT_INTERVAL.
Currently firewire-lib is lack of better rules to achieve this. So LCM of
each value of SYT_INTERVALs (=32) is applied. This can be improved for
further work.
[Fixed the compile error due to the missing "&" by tiwai]
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/firewire/amdtp.c')
-rw-r--r-- | sound/firewire/amdtp.c | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/sound/firewire/amdtp.c b/sound/firewire/amdtp.c index 3475b76..ac8c358 100644 --- a/sound/firewire/amdtp.c +++ b/sound/firewire/amdtp.c @@ -13,6 +13,7 @@ #include <linux/slab.h> #include <linux/sched.h> #include <sound/pcm.h> +#include <sound/pcm_params.h> #include <sound/rawmidi.h> #include "amdtp.h" @@ -105,6 +106,61 @@ const unsigned int amdtp_syt_intervals[CIP_SFC_COUNT] = { EXPORT_SYMBOL(amdtp_syt_intervals); /** + * amdtp_stream_add_pcm_hw_constraints - add hw constraints for PCM substream + * @s: the AMDTP stream, which must be initialized. + * @runtime: the PCM substream runtime + */ +int amdtp_stream_add_pcm_hw_constraints(struct amdtp_stream *s, + struct snd_pcm_runtime *runtime) +{ + int err; + + /* AM824 in IEC 61883-6 can deliver 24bit data */ + err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24); + if (err < 0) + goto end; + + /* + * Currently firewire-lib processes 16 packets in one software + * interrupt callback. This equals to 2msec but actually the + * interval of the interrupts has a jitter. + * Additionally, even if adding a constraint to fit period size to + * 2msec, actual calculated frames per period doesn't equal to 2msec, + * depending on sampling rate. + * Anyway, the interval to call snd_pcm_period_elapsed() cannot 2msec. + * Here let us use 5msec for safe period interrupt. + */ + err = snd_pcm_hw_constraint_minmax(runtime, + SNDRV_PCM_HW_PARAM_PERIOD_TIME, + 5000, UINT_MAX); + if (err < 0) + goto end; + + /* Non-Blocking stream has no more constraints */ + if (!(s->flags & CIP_BLOCKING)) + goto end; + + /* + * One AMDTP packet can include some frames. In blocking mode, the + * number equals to SYT_INTERVAL. So the number is 8, 16 or 32, + * depending on its sampling rate. For accurate period interrupt, it's + * preferrable to aligh period/buffer sizes to current SYT_INTERVAL. + * + * TODO: These constraints can be improved with propper rules. + * Currently apply LCM of SYT_INTEVALs. + */ + err = snd_pcm_hw_constraint_step(runtime, 0, + SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 32); + if (err < 0) + goto end; + err = snd_pcm_hw_constraint_step(runtime, 0, + SNDRV_PCM_HW_PARAM_BUFFER_SIZE, 32); +end: + return err; +} +EXPORT_SYMBOL(amdtp_stream_add_pcm_hw_constraints); + +/** * amdtp_stream_set_parameters - set stream parameters * @s: the AMDTP stream to configure * @rate: the sample rate |