USB audio with DM8168: pcm_read() returns after 10 secs if USB headset is disconnected when read is in progress

raj kumar5

Hi,

I'm using tinyalsa's pcm_read() API (ioctl SNDRV_PCM_IOCTL_READI_FRAMES in ALSA) to capture PCM audio data from a USB headset connected to USB 2.0 port of DM8168 SoC. musb is the host controller driver.

If the USB headset is disconnected while the pcm_read() is in progress, then the pcm_read() function does not return for 10 secs. I believe this is a problem with musb as I do not face this issue when USB headset is connected to a USB 3.0 port (xhci host controller driver). Please let me know if anyone has any information about this issue.

Soc: DM8168
Linux kernel: 2.6.37

Thanks,
Goutham B G

over 7 years ago

0 Pavel Botev over 7 years ago

TI__Guru**** 170625 points

Goutham,

Are you using DM816x TI EVM or custom board?

Are you using EZSDK 5.05.02.00?

Regards,
Pavel

0 raj kumar5 over 7 years ago in reply to Pavel Botev

Intellectual 360 points

Hi Pavel,

It is a custom board with DM8168 as the SoC.

PSP version: PSP04.00.00.08

Thanks,
Goutham B G

0 Pavel Botev over 7 years ago in reply to raj kumar5

TI__Guru**** 170625 points

Goutham,

Can you try to reproduce the issue on the DM816x TI EVM?

Do you use EZSDK above PSP or other SDK (i.e. DVRRDK) above PSP or it is PSP only?

Regards,
Pavel

0 raj kumar5 over 7 years ago in reply to Pavel Botev

Intellectual 360 points

Hi Pavel,

Sorry, I do not have a DM8168 EVM board. It is PSP only.

Thanks,
Goutham B G

0 Pavel Botev over 7 years ago in reply to raj kumar5

TI__Guru**** 170625 points

Goutham,

You PSP version is quite old. Can you try with the latest version of the TI81xx PSP linux kernel?

arago-project.org/.../

Regards,
Pavel

0 Dwarakesh Radhakrishnan over 7 years ago in reply to raj kumar5

Guru 13620 points

Hi Goutham,

As Pavel pointed out, it will be good if you can compare with a standard hardware and see the behavior is specific to your hardware or not.

Few debugging pointers for you to check:

Can you increase log levels in musb and check the logs ?

In file drivers/usb/musb/musb_core.c, change musb_debug level. You should start seeing lots of msub logs. There will be hub change for disconnection and the associated URBs associated with the device will be dequeued(musb_urb_dequeue()). Once they are dequeued, the pcm_read() function should exit. The pcm_read wait time out is hardcoded to 10 secs in sound/core/pcm_lib.c in function wait_for_avail().

This will be a starting point to understand what is happening, when it is disconnected. Compare the flow in xhci dequeue to understand what is happening.

0 raj kumar5 over 7 years ago in reply to Dwarakesh Radhakrishnan

Intellectual 360 points

Hi Pavel,

We have already ported all latest musb changes from the latest version of the TI81xx PSP linux kernel that can be found here : arago-project.org/.../

Thanks,
Goutham B G

0 raj kumar5 over 7 years ago in reply to raj kumar5

Intellectual 360 points

Hi Dwarakesh,

Thank you for the information. I will investigate the URB dequeue code in musb.

I wanted to know if there is any known issue (and a possible fix) in musb in this area which could be causing the problem that I have described above.

Thanks,
Goutham B G

0 Dwarakesh Radhakrishnan over 7 years ago in reply to raj kumar5

Guru 13620 points

Hi Goutham,

Best bet ways of finding it out is as Pavel suggested is to use latest package or what you tried of taking patches from the Arago git and trying out. Can you check the Arago git log and see if there is anything related to USB Disconnect or RX teardown(hope you would have done already).

0 raj kumar5 over 7 years ago in reply to Dwarakesh Radhakrishnan

Intellectual 360 points

Hi Dwarakesh,

Yes, I have ported all the patches containing musb related fixes from Arago git: arago-project.org/.../

Thanks,
Goutham B G

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USB audio with DM8168: pcm_read() returns after 10 secs if USB headset is disconnected when read is in progress