[alsa-devel] [PATCH v2] ALSA: usb-audio: work around corrupted TEAC UD-H01 feedback data

[Takashi Iwai]

At Thu,  1 May 2014 12:20:22 +0200,
Daniel Mack wrote:
> 
> From: Clemens Ladisch <clemens at ladisch.de>
> 
> The TEAC UD-H01 firmware sends wrong feedback frequency values, thus
> causing the PC to send the samples at a wrong rate, which results in
> clicks and crackles in the output.
> 
> Add a workaround to detect and fix the corruption.
> 
> Signed-off-by: Clemens Ladisch <clemens at ladisch.de>
> [mick37 at gmx.de: use sender->udh01_fb_quirk rather than
>  ep->udh01_fb_quirk in snd_usb_handle_sync_urb()]
> Reported-and-tested-by: Mick <mick37 at gmx.de>
> Reported-and-tested-by: Andrea Messa <andr.messa at tiscali.it>
> Cc: <stable at vger.kernel.org>
> ---
> Clemens, I hope you're ok that I resend this patch. With Mick's minor
> amendment (use sender->udh01_fb_quirk rather than ep->udh01_fb_quirk),
> Andrea Messa also reported success with the same hardware model.

Thanks, applied now.
Let me know if this gives any problems.


Takashi

> 
> 
> Thanks,
> Daniel
> 
>  sound/usb/card.h     |  1 +
>  sound/usb/endpoint.c | 15 ++++++++++++++-
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/usb/card.h b/sound/usb/card.h
> index 9867ab8..97acb90 100644
> --- a/sound/usb/card.h
> +++ b/sound/usb/card.h
> @@ -92,6 +92,7 @@ struct snd_usb_endpoint {
>  	unsigned int curframesize;      /* current packet size in frames (for capture) */
>  	unsigned int syncmaxsize;	/* sync endpoint packet size */
>  	unsigned int fill_max:1;	/* fill max packet size always */
> +	unsigned int udh01_fb_quirk:1;	/* corrupted feedback data */
>  	unsigned int datainterval;      /* log_2 of data packet interval */
>  	unsigned int syncinterval;	/* P for adaptive mode, 0 otherwise */
>  	unsigned char silence_value;
> diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
> index e70a87e..289f582 100644
> --- a/sound/usb/endpoint.c
> +++ b/sound/usb/endpoint.c
> @@ -471,6 +471,10 @@ struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip,
>  			ep->syncinterval = 3;
>  
>  		ep->syncmaxsize = le16_to_cpu(get_endpoint(alts, 1)->wMaxPacketSize);
> +
> +		if (chip->usb_id == USB_ID(0x0644, 0x8038) /* TEAC UD-H01 */ &&
> +		    ep->syncmaxsize == 4)
> +			ep->udh01_fb_quirk = 1;
>  	}
>  
>  	list_add_tail(&ep->list, &chip->ep_list);
> @@ -1105,7 +1109,16 @@ void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
>  	if (f == 0)
>  		return;
>  
> -	if (unlikely(ep->freqshift == INT_MIN)) {
> +	if (unlikely(sender->udh01_fb_quirk)) {
> +		/*
> +		 * The TEAC UD-H01 firmware sometimes changes the feedback value
> +		 * by +/- 0x1.0000.
> +		 */
> +		if (f < ep->freqn - 0x8000)
> +			f += 0x10000;
> +		else if (f > ep->freqn + 0x8000)
> +			f -= 0x10000;
> +	} else if (unlikely(ep->freqshift == INT_MIN)) {
>  		/*
>  		 * The first time we see a feedback value, determine its format
>  		 * by shifting it left or right until it matches the nominal
> -- 
> 1.9.0
>