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

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Message-ID: <87tu2rv0kj.wl-tiwai@suse.de>
Date:   Tue, 22 Nov 2022 09:46:20 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Michael Wu <michael@...winnertech.com>
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 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

> ---
>  sound/usb/endpoint.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
> index 310cd6fb0038..df9a91c2fc7d 100644
> --- a/sound/usb/endpoint.c
> +++ b/sound/usb/endpoint.c
> @@ -1245,7 +1245,7 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep)
>  		if (!u->urb->transfer_buffer)
>  			goto out_of_memory;
>  		u->urb->pipe = ep->pipe;
> -		u->urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
> +		u->urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
>  		u->urb->interval = 1 << ep->datainterval;
>  		u->urb->context = u;
>  		u->urb->complete = snd_complete_urb;
> @@ -1288,7 +1288,7 @@ static int sync_ep_set_params(struct snd_usb_endpoint *ep)
>  		u->urb->transfer_dma = ep->sync_dma + i * 4;
>  		u->urb->transfer_buffer_length = 4;
>  		u->urb->pipe = ep->pipe;
> -		u->urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
> +		u->urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
>  		u->urb->number_of_packets = 1;
>  		u->urb->interval = 1 << ep->syncinterval;
>  		u->urb->context = u;
> -- 
> 2.29.0
>