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Groups > linux.kernel > #1533976
| From | Takashi Iwai <tiwai@suse.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [alsa-devel] [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize |
| Date | 2016-12-01 12:30 +0100 |
| Message-ID | <sJxIR-3bK-7@gated-at.bofh.it> (permalink) |
| References | <sJ7Y6-3eC-3@gated-at.bofh.it> <sJ7Y6-3eC-1@gated-at.bofh.it> <sJuhY-PI-25@gated-at.bofh.it> <sJvxo-1QI-43@gated-at.bofh.it> <sJxzb-38x-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, 01 Dec 2016 12:16:47 +0100, Clemens Ladisch wrote: > > Takashi Iwai wrote: > > Clemens Ladisch wrote: > >> Jiada Wang wrote: > >>> since commit 57e6dae1087bbaa6b33d3dd8a8e90b63888939a3 the expected packetsize is always limited to > >>> nominal + 25%. It was discovered, that some devices > >> > >> Which devices? > >> > >>> have a much higher jitter in used packetsizes than 25% > >> > >> How high? (Please note that the USB specification restricts the jitter > >> to at most one frame in consecutive packets.) > >> > >>> which would result in BABBLE condition and dropping of packets. > >>> A better solution is so assume the jitter to be the nominal packetsize > >> > >> This solution is better for this one particular device, but how does it > >> affect normal devices, or the Scarlett 2i4 on EHCI affected? > > > > Actually, which value does this affected device in ep->maxpacksize? > > In the commit mentioned above, we changed the logic to take +25% > > frequency as the basis, and it my *reduce* if ep->maxpacksize is lower > > than that. > > > > OTOH, if ep->maxpacksize is sane, we can rely on it rather than the > > implicit +25% frequency. That said, maybe we can check > > ep->maxpacksize whether it fits within the expected range, then adapt > > it, or take +25% freq as fallback? > > You are describing how the current code behaves. The +25% limit _is_ > what the code takes as the expected range. Well, the question is what is the "sane" range. +25% doesn't fit for some devices. If maxpacksize fits without +100% as this patch suggests, can we rely on it instead? Takashi > > > I'm wondering if that unknown device just declares a wrong interval value. > > > Regards, > Clemens >
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[PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Jiada Wang <jiada_wang@mentor.com> - 2016-11-30 09:00 +0100
Re: [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Takashi Iwai <tiwai@suse.de> - 2016-11-30 10:00 +0100
Re: [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Jiada Wang <jiada_wang@mentor.com> - 2016-12-01 08:10 +0100
Re: [alsa-devel] [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Clemens Ladisch <clemens@ladisch.de> - 2016-12-01 08:50 +0100
Re: [alsa-devel] [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Takashi Iwai <tiwai@suse.de> - 2016-12-01 10:10 +0100
Re: [alsa-devel] [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Clemens Ladisch <clemens@ladisch.de> - 2016-12-01 12:20 +0100
Re: [alsa-devel] [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Takashi Iwai <tiwai@suse.de> - 2016-12-01 12:30 +0100
Re: [alsa-devel] [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Clemens Ladisch <clemens@ladisch.de> - 2016-12-01 13:00 +0100
Re: [alsa-devel] [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Clemens Ladisch <clemens@ladisch.de> - 2016-12-01 13:20 +0100
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