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author | Takashi Iwai <tiwai@suse.de> | 2021-09-29 10:08:41 +0200 |
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committer | Takashi Iwai <tiwai@suse.de> | 2021-09-30 13:55:22 +0200 |
commit | d215f63d49da9a8803af3e81acd6cad743686573 (patch) | |
tree | bb91dedf94d63f1d82e5f62a44a94396b7233030 /sound/usb | |
parent | ALSA: usb-audio: Disable low-latency mode for implicit feedback sync (diff) | |
download | linux-d215f63d49da9a8803af3e81acd6cad743686573.tar.xz linux-d215f63d49da9a8803af3e81acd6cad743686573.zip |
ALSA: usb-audio: Check available frames for the next packet size
This is yet more preparation for the upcoming changes.
Extend snd_usb_endpoint_next_packet_size() to check the available
frames and return -EAGAIN if the next packet size is equal or exceeds
the given size. This will be needed for avoiding XRUN during the low
latency operation.
As of this patch, avail=0 is passed, i.e. the check is skipped and no
behavior change.
Link: https://lore.kernel.org/r/20210929080844.11583-7-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/usb')
-rw-r--r-- | sound/usb/endpoint.c | 51 | ||||
-rw-r--r-- | sound/usb/endpoint.h | 3 | ||||
-rw-r--r-- | sound/usb/pcm.c | 2 |
3 files changed, 39 insertions, 17 deletions
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index 8e164d71d9ac..1f757a7eeafe 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -148,18 +148,23 @@ int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep) * This won't be used for implicit feedback which takes the packet size * returned from the sync source */ -static int slave_next_packet_size(struct snd_usb_endpoint *ep) +static int slave_next_packet_size(struct snd_usb_endpoint *ep, + unsigned int avail) { unsigned long flags; + unsigned int phase; int ret; if (ep->fill_max) return ep->maxframesize; spin_lock_irqsave(&ep->lock, flags); - ep->phase = (ep->phase & 0xffff) - + (ep->freqm << ep->datainterval); - ret = min(ep->phase >> 16, ep->maxframesize); + phase = (ep->phase & 0xffff) + (ep->freqm << ep->datainterval); + ret = min(phase >> 16, ep->maxframesize); + if (avail && ret >= avail) + ret = -EAGAIN; + else + ep->phase = phase; spin_unlock_irqrestore(&ep->lock, flags); return ret; @@ -169,20 +174,25 @@ static int slave_next_packet_size(struct snd_usb_endpoint *ep) * Return the number of samples to be sent in the next packet * for adaptive and synchronous endpoints */ -static int next_packet_size(struct snd_usb_endpoint *ep) +static int next_packet_size(struct snd_usb_endpoint *ep, unsigned int avail) { + unsigned int sample_accum; int ret; if (ep->fill_max) return ep->maxframesize; - ep->sample_accum += ep->sample_rem; - if (ep->sample_accum >= ep->pps) { - ep->sample_accum -= ep->pps; + sample_accum += ep->sample_rem; + if (sample_accum >= ep->pps) { + sample_accum -= ep->pps; ret = ep->packsize[1]; } else { ret = ep->packsize[0]; } + if (avail && ret >= avail) + ret = -EAGAIN; + else + ep->sample_accum = sample_accum; return ret; } @@ -190,16 +200,27 @@ static int next_packet_size(struct snd_usb_endpoint *ep) /* * snd_usb_endpoint_next_packet_size: Return the number of samples to be sent * in the next packet + * + * If the size is equal or exceeds @avail, don't proceed but return -EAGAIN + * Exception: @avail = 0 for skipping the check. */ int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep, - struct snd_urb_ctx *ctx, int idx) + struct snd_urb_ctx *ctx, int idx, + unsigned int avail) { - if (ctx->packet_size[idx]) - return ctx->packet_size[idx]; - else if (ep->sync_source) - return slave_next_packet_size(ep); + unsigned int packet; + + packet = ctx->packet_size[idx]; + if (packet) { + if (avail && packet >= avail) + return -EAGAIN; + return packet; + } + + if (ep->sync_source) + return slave_next_packet_size(ep, avail); else - return next_packet_size(ep); + return next_packet_size(ep, avail); } static void call_retire_callback(struct snd_usb_endpoint *ep, @@ -263,7 +284,7 @@ static void prepare_silent_urb(struct snd_usb_endpoint *ep, unsigned int length; int counts; - counts = snd_usb_endpoint_next_packet_size(ep, ctx, i); + counts = snd_usb_endpoint_next_packet_size(ep, ctx, i, 0); length = counts * ep->stride; /* number of silent bytes */ offset = offs * ep->stride + extra * i; urb->iso_frame_desc[i].offset = offset; diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h index a1099ec37e1c..1f1a72535a64 100644 --- a/sound/usb/endpoint.h +++ b/sound/usb/endpoint.h @@ -46,6 +46,7 @@ void snd_usb_endpoint_free_all(struct snd_usb_audio *chip); int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep); int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep, - struct snd_urb_ctx *ctx, int idx); + struct snd_urb_ctx *ctx, int idx, + unsigned int avail); #endif /* __USBAUDIO_ENDPOINT_H */ diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c index ec7eeb1b82b8..8ad48c35c559 100644 --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -1365,7 +1365,7 @@ static void prepare_playback_urb(struct snd_usb_substream *subs, spin_lock_irqsave(&subs->lock, flags); subs->frame_limit += ep->max_urb_frames; for (i = 0; i < ctx->packets; i++) { - counts = snd_usb_endpoint_next_packet_size(ep, ctx, i); + counts = snd_usb_endpoint_next_packet_size(ep, ctx, i, 0); /* set up descriptor */ urb->iso_frame_desc[i].offset = frames * stride; urb->iso_frame_desc[i].length = counts * stride; |