Asynchronous audio USB chips: choppy playback since 3.8-rc7

Asynchronous audio USB chips: choppy playback since 3.8-rc7

[David Henningsson]

Hi ALSA developers,

Just to get your attention here on what seems to be an USB audio 
regression.

The bug is described in detail here:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all

Quoting the bug:

"
This bug seems to affect only a certain kind of hardware, which is 
called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
called "Synchronous USB DAC", uses the clock hosted by the mother board, 
which is not affected by this bug.

When this bug affects an asynchronous USB DAC, the audio played by the 
DAC is constantly interrupted. The playback itself does not stop, but 
the output becomes discontinous, filling with constant crackling noises, 
destroying everything the DAC plays.
"

According to the bug reporter, which seems to have done quite a bit of 
research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
kernels and the bug also lists a few commits which could be the cause, 
none under sound/usb though.




-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic

Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Daniel Mack]

Hi David,

On 03.04.2013 12:15, David Henningsson wrote:
> Just to get your attention here on what seems to be an USB audio 
> regression.
> 
> The bug is described in detail here:
> 
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
> 
> Quoting the bug:
> 
> "
> This bug seems to affect only a certain kind of hardware, which is 
> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
> which is not affected by this bug.
> 
> When this bug affects an asynchronous USB DAC, the audio played by the 
> DAC is constantly interrupted. The playback itself does not stop, but 
> the output becomes discontinous, filling with constant crackling noises, 
> destroying everything the DAC plays.
> "
> 
> According to the bug reporter, which seems to have done quite a bit of 
> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
> kernels and the bug also lists a few commits which could be the cause, 
> none under sound/usb though.

There were no relevant changes for snd-usb between the two versions
mentioned. The only patches that come in mind in this time window are:

 3e619d041 "USB: EHCI: fix bug in scheduling periodic split transfers"
 b09a61cc0 "USB: EHCI: fix for leaking isochronous data"

And they have both been back-ported to stable. Copied Alan for reference.

Any chance some of the bug reporters could try and revert exactly those
for testing?


Thanks,
Daniel

Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Takashi Iwai]

At Wed, 03 Apr 2013 12:15:25 +0200,
David Henningsson wrote:
> 
> Hi ALSA developers,
> 
> Just to get your attention here on what seems to be an USB audio 
> regression.
> 
> The bug is described in detail here:
> 
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
> 
> Quoting the bug:
> 
> "
> This bug seems to affect only a certain kind of hardware, which is 
> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
> which is not affected by this bug.
> 
> When this bug affects an asynchronous USB DAC, the audio played by the 
> DAC is constantly interrupted. The playback itself does not stop, but 
> the output becomes discontinous, filling with constant crackling noises, 
> destroying everything the DAC plays.
> "
> 
> According to the bug reporter, which seems to have done quite a bit of 
> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
> kernels and the bug also lists a few commits which could be the cause, 
> none under sound/usb though.

Yes, there is no commits regarding usb-audio itself between 3.8-rc6
and rc7, so the likely culprit is in drivers/usb (usually either
drivers/usb/host or drivers/usb/core).  There are a bunch of changes
there, so further bisection would be appreciated.


Takashi

Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Michael Trimarchi]

Hi Daniel

On 03/04/13 12:23, Daniel Mack wrote:
> Hi David,
> 
> On 03.04.2013 12:15, David Henningsson wrote:
>> Just to get your attention here on what seems to be an USB audio 
>> regression.
>>
>> The bug is described in detail here:
>>
>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
>>
>> Quoting the bug:
>>
>> "
>> This bug seems to affect only a certain kind of hardware, which is 
>> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
>> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
>> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
>> which is not affected by this bug.
>>
>> When this bug affects an asynchronous USB DAC, the audio played by the 
>> DAC is constantly interrupted. The playback itself does not stop, but 
>> the output becomes discontinous, filling with constant crackling noises, 
>> destroying everything the DAC plays.
>> "
>>
>> According to the bug reporter, which seems to have done quite a bit of 
>> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
>> kernels and the bug also lists a few commits which could be the cause, 
>> none under sound/usb though.
> 
> There were no relevant changes for snd-usb between the two versions
> mentioned. The only patches that come in mind in this time window are:
> 
>  3e619d041 "USB: EHCI: fix bug in scheduling periodic split transfers"
>  b09a61cc0 "USB: EHCI: fix for leaking isochronous data"

This last one, doesn't give me any problem, just a memory leak and not a choppy
playback (tested on 48Khz, 96Khz, 192Khz 32bit on OMAP3 device) and I don't
think that it can be the reason of the problem.

http://www.m2tech.biz/hiface_dac.html

Michael


> 
> And they have both been back-ported to stable. Copied Alan for reference.
> 
> Any chance some of the bug reporters could try and revert exactly those
> for testing?
> 
> 
> Thanks,
> Daniel
> 
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@alsa-project.org
> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
> 

Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Michael Trimarchi]

Hi Daniel

On 03/04/13 15:55, Michael Trimarchi wrote:
> Hi Daniel
> 
> On 03/04/13 12:23, Daniel Mack wrote:
>> Hi David,
>>
>> On 03.04.2013 12:15, David Henningsson wrote:
>>> Just to get your attention here on what seems to be an USB audio 
>>> regression.
>>>
>>> The bug is described in detail here:
>>>
>>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
>>>
>>> Quoting the bug:
>>>
>>> "
>>> This bug seems to affect only a certain kind of hardware, which is 
>>> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
>>> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
>>> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
>>> which is not affected by this bug.
>>>
>>> When this bug affects an asynchronous USB DAC, the audio played by the 
>>> DAC is constantly interrupted. The playback itself does not stop, but 
>>> the output becomes discontinous, filling with constant crackling noises, 
>>> destroying everything the DAC plays.
>>> "
>>>
>>> According to the bug reporter, which seems to have done quite a bit of 
>>> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
>>> kernels and the bug also lists a few commits which could be the cause, 
>>> none under sound/usb though.
>>
>> There were no relevant changes for snd-usb between the two versions
>> mentioned. The only patches that come in mind in this time window are:
>>
>>  3e619d041 "USB: EHCI: fix bug in scheduling periodic split transfers"
>>  b09a61cc0 "USB: EHCI: fix for leaking isochronous data"
> 
> This last one, doesn't give me any problem, just a memory leak and not a choppy
> playback (tested on 48Khz, 96Khz, 192Khz 32bit on OMAP3 device) and I don't
> think that it can be the reason of the problem.

Sorry the comment was for a bug that is not included in this list and recently fixed.
USB: EHCI: fix bug in iTD/siTD DMA pool allocation

Michael

> 
> http://www.m2tech.biz/hiface_dac.html
> 
> Michael
> 
> 
>>
>> And they have both been back-ported to stable. Copied Alan for reference.
>>
>> Any chance some of the bug reporters could try and revert exactly those
>> for testing?
>>
>>
>> Thanks,
>> Daniel
>>
>> _______________________________________________
>> Alsa-devel mailing list
>> Alsa-devel@alsa-project.org
>> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
>>
> 

Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Daniel Mack]

Hi Michael,

On 03.04.2013 16:11, Michael Trimarchi wrote:
> On 03/04/13 15:55, Michael Trimarchi wrote:
>> On 03/04/13 12:23, Daniel Mack wrote:
>>> Hi David,
>>>
>>> On 03.04.2013 12:15, David Henningsson wrote:
>>>> Just to get your attention here on what seems to be an USB audio 
>>>> regression.
>>>>
>>>> The bug is described in detail here:
>>>>
>>>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
>>>>
>>>> Quoting the bug:
>>>>
>>>> "
>>>> This bug seems to affect only a certain kind of hardware, which is 
>>>> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
>>>> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
>>>> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
>>>> which is not affected by this bug.
>>>>
>>>> When this bug affects an asynchronous USB DAC, the audio played by the 
>>>> DAC is constantly interrupted. The playback itself does not stop, but 
>>>> the output becomes discontinous, filling with constant crackling noises, 
>>>> destroying everything the DAC plays.
>>>> "
>>>>
>>>> According to the bug reporter, which seems to have done quite a bit of 
>>>> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
>>>> kernels and the bug also lists a few commits which could be the cause, 
>>>> none under sound/usb though.
>>>
>>> There were no relevant changes for snd-usb between the two versions
>>> mentioned. The only patches that come in mind in this time window are:
>>>
>>>  3e619d041 "USB: EHCI: fix bug in scheduling periodic split transfers"
>>>  b09a61cc0 "USB: EHCI: fix for leaking isochronous data"
>>
>> This last one, doesn't give me any problem, just a memory leak and not a choppy
>> playback (tested on 48Khz, 96Khz, 192Khz 32bit on OMAP3 device) and I don't
>> think that it can be the reason of the problem.

Is OMAP3 at all a platform that is affected by the bug? It seems the
effect is only seen on some special host controller hardware anyway.

> Sorry the comment was for a bug that is not included in this list and recently fixed.
> USB: EHCI: fix bug in iTD/siTD DMA pool allocation

Sorry, you lost me. So what's the status of this issue now? Does "USB:
EHCI: fix bug in iTD/siTD DMA pool allocation" fix it?

If not - and assuming you can reproduce the bug - which patches of the
two I mentioned did you revert, and what was the effect of that? Did you
try and remove both as well?


Thanks,
Daniel

Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Michael Trimarchi]

Hi Daniel

On 03/04/13 17:00, Daniel Mack wrote:
> Hi Michael,
> 
> On 03.04.2013 16:11, Michael Trimarchi wrote:
>> On 03/04/13 15:55, Michael Trimarchi wrote:
>>> On 03/04/13 12:23, Daniel Mack wrote:
>>>> Hi David,
>>>>
>>>> On 03.04.2013 12:15, David Henningsson wrote:
>>>>> Just to get your attention here on what seems to be an USB audio 
>>>>> regression.
>>>>>
>>>>> The bug is described in detail here:
>>>>>
>>>>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
>>>>>
>>>>> Quoting the bug:
>>>>>
>>>>> "
>>>>> This bug seems to affect only a certain kind of hardware, which is 
>>>>> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
>>>>> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
>>>>> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
>>>>> which is not affected by this bug.
>>>>>
>>>>> When this bug affects an asynchronous USB DAC, the audio played by the 
>>>>> DAC is constantly interrupted. The playback itself does not stop, but 
>>>>> the output becomes discontinous, filling with constant crackling noises, 
>>>>> destroying everything the DAC plays.
>>>>> "
>>>>>
>>>>> According to the bug reporter, which seems to have done quite a bit of 
>>>>> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
>>>>> kernels and the bug also lists a few commits which could be the cause, 
>>>>> none under sound/usb though.
>>>>
>>>> There were no relevant changes for snd-usb between the two versions
>>>> mentioned. The only patches that come in mind in this time window are:
>>>>
>>>>  3e619d041 "USB: EHCI: fix bug in scheduling periodic split transfers"
>>>>  b09a61cc0 "USB: EHCI: fix for leaking isochronous data"
>>>
>>> This last one, doesn't give me any problem, just a memory leak and not a choppy
>>> playback (tested on 48Khz, 96Khz, 192Khz 32bit on OMAP3 device) and I don't
>>> think that it can be the reason of the problem.
> 
> Is OMAP3 at all a platform that is affected by the bug? It seems the
> effect is only seen on some special host controller hardware anyway.
> 

Yes, omap3 ehci and m2tech products is not affected and I'm testing a dac with internal clock.

>> Sorry the comment was for a bug that is not included in this list and recently fixed.
>> USB: EHCI: fix bug in iTD/siTD DMA pool allocation
> 
> Sorry, you lost me. So what's the status of this issue now? Does "USB:
> EHCI: fix bug in iTD/siTD DMA pool allocation" fix it?

With or without it, I don't have any choppy audio and this is not a fix
of this bug.

> 
> If not - and assuming you can reproduce the bug - which patches of the
> two I mentioned did you revert, and what was the effect of that? Did you
> try and remove both as well?

In my version I have the other two commits applied. I doubt that these two
commits are the reason of the choppy audio. What I can do, it test it on my
laptop tomorrow and send feedback result

Michael



> 
> 
> Thanks,
> Daniel
>

Re: [alsa-devel] Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Daniel Mack]

On 03.04.2013 17:19, Michael Trimarchi wrote:
> Hi Daniel
> 
> On 03/04/13 17:00, Daniel Mack wrote:
>> Hi Michael,
>>
>> On 03.04.2013 16:11, Michael Trimarchi wrote:
>>> On 03/04/13 15:55, Michael Trimarchi wrote:
>>>> On 03/04/13 12:23, Daniel Mack wrote:
>>>>> Hi David,
>>>>>
>>>>> On 03.04.2013 12:15, David Henningsson wrote:
>>>>>> Just to get your attention here on what seems to be an USB audio 
>>>>>> regression.
>>>>>>
>>>>>> The bug is described in detail here:
>>>>>>
>>>>>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
>>>>>>
>>>>>> Quoting the bug:
>>>>>>
>>>>>> "
>>>>>> This bug seems to affect only a certain kind of hardware, which is 
>>>>>> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
>>>>>> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
>>>>>> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
>>>>>> which is not affected by this bug.
>>>>>>
>>>>>> When this bug affects an asynchronous USB DAC, the audio played by the 
>>>>>> DAC is constantly interrupted. The playback itself does not stop, but 
>>>>>> the output becomes discontinous, filling with constant crackling noises, 
>>>>>> destroying everything the DAC plays.
>>>>>> "
>>>>>>
>>>>>> According to the bug reporter, which seems to have done quite a bit of 
>>>>>> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
>>>>>> kernels and the bug also lists a few commits which could be the cause, 
>>>>>> none under sound/usb though.
>>>>>
>>>>> There were no relevant changes for snd-usb between the two versions
>>>>> mentioned. The only patches that come in mind in this time window are:
>>>>>
>>>>>  3e619d041 "USB: EHCI: fix bug in scheduling periodic split transfers"
>>>>>  b09a61cc0 "USB: EHCI: fix for leaking isochronous data"
>>>>
>>>> This last one, doesn't give me any problem, just a memory leak and not a choppy
>>>> playback (tested on 48Khz, 96Khz, 192Khz 32bit on OMAP3 device) and I don't
>>>> think that it can be the reason of the problem.
>>
>> Is OMAP3 at all a platform that is affected by the bug? It seems the
>> effect is only seen on some special host controller hardware anyway.
>>
> 
> Yes, omap3 ehci and m2tech products is not affected and I'm testing a dac with internal clock.
> 
>>> Sorry the comment was for a bug that is not included in this list and recently fixed.
>>> USB: EHCI: fix bug in iTD/siTD DMA pool allocation
>>
>> Sorry, you lost me. So what's the status of this issue now? Does "USB:
>> EHCI: fix bug in iTD/siTD DMA pool allocation" fix it?
> 
> With or without it, I don't have any choppy audio and this is not a fix
> of this bug.

If you cannot reproduce the bug, how can you reproduce a fix then?

Also, if all users of snd-usb would be affected since 3.8-rc7, I'm sure
this mailing list would be full of reports.

The bug is only triggered by some sort of hardware (appearantly such
with an internal clock), and only with some patch applied that went in
between 3.8-rc6 and 3.8-rc7.

Someone with hardware that shows the bug has to bisect between these two
tags please. Given the number of patches between them (230), that
shouldn't take long.

ALSA is certainly not the culprit here, as there where only ASoC patches
in that range. I'm copying the linux-usb ML.


Thanks,
Daniel
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Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Daniel Mack]

On 03.04.2013 12:25, Takashi Iwai wrote:
> At Wed, 03 Apr 2013 12:15:25 +0200,
> David Henningsson wrote:
>>
>> Hi ALSA developers,
>>
>> Just to get your attention here on what seems to be an USB audio 
>> regression.
>>
>> The bug is described in detail here:
>>
>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
>>
>> Quoting the bug:
>>
>> "
>> This bug seems to affect only a certain kind of hardware, which is 
>> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
>> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
>> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
>> which is not affected by this bug.
>>
>> When this bug affects an asynchronous USB DAC, the audio played by the 
>> DAC is constantly interrupted. The playback itself does not stop, but 
>> the output becomes discontinous, filling with constant crackling noises, 
>> destroying everything the DAC plays.
>> "
>>
>> According to the bug reporter, which seems to have done quite a bit of 
>> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
>> kernels and the bug also lists a few commits which could be the cause, 
>> none under sound/usb though.
> 
> Yes, there is no commits regarding usb-audio itself between 3.8-rc6
> and rc7, so the likely culprit is in drivers/usb (usually either
> drivers/usb/host or drivers/usb/core).  There are a bunch of changes
> there, so further bisection would be appreciated.

Ok, Joseph Salisbury has build some bisection kernels, and Tyson Tan
relentlessly tested all of them, and it turns out that

3e619d0415 ("USB: EHCI: fix bug in scheduling periodic split transfers")

Is the first bad commit. Also, reverting this commit from the current
mainline head makes the problem disappear.

Alan, any idea?

  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110


Thanks,
Daniel

Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Alan Stern]

On Fri, 19 Apr 2013, Daniel Mack wrote:

> On 03.04.2013 12:25, Takashi Iwai wrote:
> > At Wed, 03 Apr 2013 12:15:25 +0200,
> > David Henningsson wrote:
> >>
> >> Hi ALSA developers,
> >>
> >> Just to get your attention here on what seems to be an USB audio 
> >> regression.
> >>
> >> The bug is described in detail here:
> >>
> >> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
> >>
> >> Quoting the bug:
> >>
> >> "
> >> This bug seems to affect only a certain kind of hardware, which is 
> >> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
> >> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
> >> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
> >> which is not affected by this bug.
> >>
> >> When this bug affects an asynchronous USB DAC, the audio played by the 
> >> DAC is constantly interrupted. The playback itself does not stop, but 
> >> the output becomes discontinous, filling with constant crackling noises, 
> >> destroying everything the DAC plays.
> >> "
> >>
> >> According to the bug reporter, which seems to have done quite a bit of 
> >> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
> >> kernels and the bug also lists a few commits which could be the cause, 
> >> none under sound/usb though.
> > 
> > Yes, there is no commits regarding usb-audio itself between 3.8-rc6
> > and rc7, so the likely culprit is in drivers/usb (usually either
> > drivers/usb/host or drivers/usb/core).  There are a bunch of changes
> > there, so further bisection would be appreciated.
> 
> Ok, Joseph Salisbury has build some bisection kernels, and Tyson Tan
> relentlessly tested all of them, and it turns out that
> 
> 3e619d0415 ("USB: EHCI: fix bug in scheduling periodic split transfers")
> 
> Is the first bad commit. Also, reverting this commit from the current
> mainline head makes the problem disappear.
> 
> Alan, any idea?
> 
>   https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110

No ideas as to the cause.

For debugging, it would help to see a usbmon trace from a kernel where 
the problem occurs, together with a trace from another kernel where the 
problem does not occur.

Alan Stern

Re: [alsa-devel] Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Alan Stern]

On Fri, 19 Apr 2013, Daniel Mack wrote:

> On 03.04.2013 12:25, Takashi Iwai wrote:
> > At Wed, 03 Apr 2013 12:15:25 +0200,
> > David Henningsson wrote:
> >>
> >> Hi ALSA developers,
> >>
> >> Just to get your attention here on what seems to be an USB audio 
> >> regression.
> >>
> >> The bug is described in detail here:
> >>
> >> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
> >>
> >> Quoting the bug:
> >>
> >> "
> >> This bug seems to affect only a certain kind of hardware, which is 
> >> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such 
> >> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so 
> >> called "Synchronous USB DAC", uses the clock hosted by the mother board, 
> >> which is not affected by this bug.
> >>
> >> When this bug affects an asynchronous USB DAC, the audio played by the 
> >> DAC is constantly interrupted. The playback itself does not stop, but 
> >> the output becomes discontinous, filling with constant crackling noises, 
> >> destroying everything the DAC plays.
> >> "
> >>
> >> According to the bug reporter, which seems to have done quite a bit of 
> >> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable 
> >> kernels and the bug also lists a few commits which could be the cause, 
> >> none under sound/usb though.
> > 
> > Yes, there is no commits regarding usb-audio itself between 3.8-rc6
> > and rc7, so the likely culprit is in drivers/usb (usually either
> > drivers/usb/host or drivers/usb/core).  There are a bunch of changes
> > there, so further bisection would be appreciated.
> 
> Ok, Joseph Salisbury has build some bisection kernels, and Tyson Tan
> relentlessly tested all of them, and it turns out that
> 
> 3e619d0415 ("USB: EHCI: fix bug in scheduling periodic split transfers")
> 
> Is the first bad commit. Also, reverting this commit from the current
> mainline head makes the problem disappear.
> 
> Alan, any idea?
> 
>   https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110

No ideas as to the cause.

For debugging, it would help to see a usbmon trace from a kernel where 
the problem occurs, together with a trace from another kernel where the 
problem does not occur.

Alan Stern

_______________________________________________
Alsa-devel mailing list
Alsa-devel@alsa-project.org
http://mailman.alsa-project.org/mailman/listinfo/alsa-devel

Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[David Henningsson]

On 04/19/2013 10:48 PM, Alan Stern wrote:
> On Fri, 19 Apr 2013, Daniel Mack wrote:
>
>> On 03.04.2013 12:25, Takashi Iwai wrote:
>>> At Wed, 03 Apr 2013 12:15:25 +0200,
>>> David Henningsson wrote:
>>>>
>>>> Hi ALSA developers,
>>>>
>>>> Just to get your attention here on what seems to be an USB audio
>>>> regression.
>>>>
>>>> The bug is described in detail here:
>>>>
>>>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110?comments=all
>>>>
>>>> Quoting the bug:
>>>>
>>>> "
>>>> This bug seems to affect only a certain kind of hardware, which is
>>>> called "Asynchronous USB Digital Audio Codec (DAC)". It's said that such
>>>> a DAC hosts the clock itself (USB Device Host). An ordinary DAC, so
>>>> called "Synchronous USB DAC", uses the clock hosted by the mother board,
>>>> which is not affected by this bug.
>>>>
>>>> When this bug affects an asynchronous USB DAC, the audio played by the
>>>> DAC is constantly interrupted. The playback itself does not stop, but
>>>> the output becomes discontinous, filling with constant crackling noises,
>>>> destroying everything the DAC plays.
>>>> "
>>>>
>>>> According to the bug reporter, which seems to have done quite a bit of
>>>> research, this started between 3.8-rc6 and 3.8-rc7 as well as stable
>>>> kernels and the bug also lists a few commits which could be the cause,
>>>> none under sound/usb though.
>>>
>>> Yes, there is no commits regarding usb-audio itself between 3.8-rc6
>>> and rc7, so the likely culprit is in drivers/usb (usually either
>>> drivers/usb/host or drivers/usb/core).  There are a bunch of changes
>>> there, so further bisection would be appreciated.
>>
>> Ok, Joseph Salisbury has build some bisection kernels, and Tyson Tan
>> relentlessly tested all of them, and it turns out that
>>
>> 3e619d0415 ("USB: EHCI: fix bug in scheduling periodic split transfers")
>>
>> Is the first bad commit. Also, reverting this commit from the current
>> mainline head makes the problem disappear.
>>
>> Alan, any idea?
>>
>>    https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110
>
> No ideas as to the cause.
>
> For debugging, it would help to see a usbmon trace from a kernel where
> the problem occurs, together with a trace from another kernel where the
> problem does not occur.
>
> Alan Stern

First, thanks for looking at this bug.

While a long-term solution is being discussed, this patch went to stable 
too, where it is causing regressions. Would it be okay just to revert 
this patch in the next stable series? (Even if this was a bug fix, few 
people seem to have noticed?) Or do you envision something else 
happening but the original -ENOSPC error showing up, due to other stuff 
that went to stable at the same time?


-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic

Re: Asynchronous audio USB chips: choppy playback since 3.8-rc7

[Alan Stern]

On Wed, 24 Apr 2013, David Henningsson wrote:

> >> Ok, Joseph Salisbury has build some bisection kernels, and Tyson Tan
> >> relentlessly tested all of them, and it turns out that
> >>
> >> 3e619d0415 ("USB: EHCI: fix bug in scheduling periodic split transfers")
> >>
> >> Is the first bad commit. Also, reverting this commit from the current
> >> mainline head makes the problem disappear.
> >>
> >> Alan, any idea?
> >>
> >>    https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110
> >
> > No ideas as to the cause.
> >
> > For debugging, it would help to see a usbmon trace from a kernel where
> > the problem occurs, together with a trace from another kernel where the
> > problem does not occur.
> >
> > Alan Stern
> 
> First, thanks for looking at this bug.
> 
> While a long-term solution is being discussed, this patch went to stable 
> too, where it is causing regressions. Would it be okay just to revert 
> this patch in the next stable series? (Even if this was a bug fix, few 
> people seem to have noticed?) Or do you envision something else 
> happening but the original -ENOSPC error showing up, due to other stuff 
> that went to stable at the same time?

I think reverting it from stable won't cause any new problems to show 
up (although the original problem will return, obviously).  Go ahead.

At the same time, it would be nice to know that some people are really
carrying out tests to find the reason for the new problem.  Otherwise
we end up with this commit reverted and nobody trying to figure out how
to fix the original bug correctly.

Alan Stern