linux-kernel - Re: [PATCH] ALSA: usb-audio: fix urb timeout with URB_ISO

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Date:   Tue, 22 Nov 2022 16:54:31 +0800
From:   Michael Wu <michael@...winnertech.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     perex@...ex.cz, tiwai@...e.com, aichao@...inos.cn,
        wanjiabing@...o.com, ubizjak@...il.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ALSA: usb-audio: fix urb timeout with URB_ISO_ASAP flag

On 11/22/2022 4:46 PM, Takashi Iwai wrote:
> On Tue, 22 Nov 2022 09:20:40 +0100,
> Michael Wu wrote:
>>
>> When the loglevel is greater than 4, with a long messages printed on the
>> console while playing or recording audios, the usb controller may become
>> abnormal.
>> `usb 1-2: timeout: still 1 active urbs on EP #1`
>>
>> Fix it by configuring the transfer_flags URB_ISO_ASAP flag.
>>
>> Signed-off-by: Michael Wu <michael@...winnertech.com>
> 
> Hrm, that's somewhat backward action to the change we've done years
> ago, commit c75c5ab575af7db707689cdbb5a5c458e9a034bb:
> 
>      ALSA: USB: adjust for changed 3.8 USB API
>      
>      The recent changes in the USB API ("implement new semantics for
>      URB_ISO_ASAP") made the former meaning of the URB_ISO_ASAP flag the
>      default, and changed this flag to mean that URBs can be delayed.
>      This is not the behaviour wanted by any of the audio drivers because
>      it leads to discontinuous playback with very small period sizes.
>      Therefore, our URBs need to be submitted without this flag.
> 
> I rather suspect that your problem is in the USB controller side.
> 
> 
> thanks,
> 
> Takashi
> 
Dear Takashi, thanks for the reminding. Let me check...

-- 
Regards,
Michael Wu