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authorAndreas Pape <apape@de.adit-jv.com>2016-12-06 14:46:14 +0900
committerTakashi Iwai <tiwai@suse.de>2016-12-06 13:55:59 +0100
commitfd1a5059610cd3887f1050171a840ca864108730 (patch)
tree749a58c5972b72aec1a78c765f2f9cf4b3e1a776 /sound/usb/endpoint.c
parent1e2e3fe480064ca33186e5a923beaa160efed35d (diff)
downloadop-kernel-dev-fd1a5059610cd3887f1050171a840ca864108730.zip
op-kernel-dev-fd1a5059610cd3887f1050171a840ca864108730.tar.gz
ALSA: usb-audio: more tolerant packetsize
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 (Android audio accessory) 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> Acked-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/usb/endpoint.c')
-rw-r--r--sound/usb/endpoint.c4
1 files 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
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