From: Takashi Iwai tiwai@suse.de
commit d215f63d49da9a8803af3e81acd6cad743686573 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- sound/usb/endpoint.c | 51 ++++++++++++++++++++++++++++++++++++--------------- sound/usb/endpoint.h | 3 ++- sound/usb/pcm.c | 2 +- 3 files changed, 39 insertions(+), 17 deletions(-)
--- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -148,18 +148,23 @@ int snd_usb_endpoint_implicit_feedback_s * 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 * 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_u /* * 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 sn 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; --- a/sound/usb/endpoint.h +++ b/sound/usb/endpoint.h @@ -46,6 +46,7 @@ void snd_usb_endpoint_free_all(struct sn
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 */ --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -1365,7 +1365,7 @@ static void prepare_playback_urb(struct 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;