ALSA: usb-audio: work around corrupted TEAC UD-H01 feedback data

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 15 insertions, 1 deletions

diff --git a/sound/usb/card.h b/sound/usb/card.h
index 9867ab866857..97acb906acc2 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 e70a87e0d9fe..289f582c9130 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