From: Andreas Pape apape@de.adit-jv.com
since commit 57e6dae1087b ("ALSA: usb-audio: do not trust too-big wMaxPacketSize values"), the expected packetsize is always limited to nominal + 25%. It was discovered, that some devices have a much higher jitter in used packetsizes than 25% which would result in BABBLE condition and dropping of packets. A better solution is so assume the jitter to be the nominal packetsize: -one nearly empty packet followed by a almost 150% sized one.
V2: changed to assume max frequency is +50 of nominal packetsize.
Signed-off-by: Andreas Pape apape@de.adit-jv.com Signed-off-by: Jiada Wang jiada_wang@mentor.com --- sound/usb/endpoint.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index c470251..a2931f4 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -632,8 +632,8 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep, ep->stride = frame_bits >> 3; ep->silence_value = pcm_format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0;
- /* assume max. frequency is 25% higher than nominal */ - ep->freqmax = ep->freqn + (ep->freqn >> 2); + /* assume max. frequency is 50% higher than nominal */ + ep->freqmax = ep->freqn + (ep->freqn >> 1); /* Round up freqmax to nearest integer in order to calculate maximum * packet size, which must represent a whole number of frames. * This is accomplished by adding 0x0.ffff before converting the