[PATCH 3.10 042/103] ALSA: usb-audio: work around corrupted TEAC UD-H01 feedback data

Greg Kroah-Hartman
2014-06-04T23:25:05Z

From: Clemens Ladisch <clemens@ladisch.de>

commit 7040b6d1febfdbd9c1595efb751d492cd2503f96 upstream.

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@ladisch.de>
[mick37@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@gmx.de>
Reported-and-tested-by: Andrea Messa <andr.messa@tiscali.it>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
sound/usb/card.h | 1 +
sound/usb/endpoint.c | 15 ++++++++++++++-
2 files changed, 15 insertions(+), 1 deletion(-)

--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -90,6 +90,7 @@ 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;
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -467,6 +467,10 @@ struct snd_usb_endpoint *snd_usb_add_end
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);
@@ -1075,7 +1079,16 @@ void snd_usb_handle_sync_urb(struct snd_
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