On 2016-03-03, Bin Liu <b-liu@xxxxxx> wrote: >> Using next-20160302 I can very reliably hit this warning on an AM335x >> BeagleBone by playing a short audio file over USB-Audio: >> >> $ aplay -Dplughw:1,0 -r 44100 -c 2 -f S16_LE /usr/share/sounds/alsa/Front_Center.wav >> >> $ aplay -l >> **** List of PLAYBACK Hardware Devices **** >> card 1: Audio [USB Audio], device 0: USB Audio [USB Audio] >> Subdevices: 1/1 >> Subdevice #0: subdevice #0 >> >> The audio file is part of the alsa-utils package. The USB-Audio >> device is never disconnected. Simply playing the file triggers the >> warning. Any hints/suggestions how I should debug this? > > In general, it seems this tx fifo flush error has been there for > years, it happens when tearing down an active endpoint in some unknown > conditions. But I haven't seen a such case in which musb stops > working. Actually, I am tracking down an issue where musb _does_ stop working. With the above "aplay" example, I can reproduce a hang with the musb on v3.19 and v4.0. Sometimes it takes up to an hour to reproduce the hang, so I am slowly moving to newer kernels to see how far I can reproduce the hang. I have not been able to reproduce a hang with next-20160302 (yet?), but I do get your warning and the backtrace looks very similar to what I see in the hang situation on the older kernel versions. > In this case, does musb still work or is audio playback broken after > the warning message? In this (next-20160302) case musb does continue to work. In my debugging of the older kernels I can perfectly identify when the situation for a potential hang happens. Most of the time it does not hang there, but 100% of the hangs were in that exact situation. So I suspect a race condition exists there. > Does the issue happen in any previous kernel? Trying to think if there > is any regression in next-20160302... I will continue trying to reproduce the hang with newer kernels. I haven't tried anything between v4.0 and next-20160302 yet. I will post again when I have more data. John Ogness -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
