1 files changed, 16 insertions, 3 deletions

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index acc12f004c23..2c971858d6b7 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -387,11 +387,13 @@ static int snd_usb_fasttrackpro_boot_quirk(struct usb_device *dev)
                  * rules
                  */
                 err = usb_driver_set_configuration(dev, 2);
-                if (err < 0) {
+                if (err < 0)
                         snd_printdd("error usb_driver_set_configuration: %d\n",
                                     err);
-                        return -ENODEV;
-                }
+                /* Always return an error, so that we stop creating a device
+                   that will just be destroyed and recreated with a new
+                   configuration */
+                return -ENODEV;
         } else
                 snd_printk(KERN_INFO "usb-audio: Fast Track Pro config OK\n");
 
@@ -859,6 +861,17 @@ void snd_usb_endpoint_start_quirk(struct snd_usb_endpoint *ep)
         if ((le16_to_cpu(ep->chip->dev->descriptor.idVendor) == 0x23ba) &&
             ep->type == SND_USB_ENDPOINT_TYPE_SYNC)
                 ep->skip_packets = 4;
+
+        /*
+         * M-Audio Fast Track C400 - when packets are not skipped, real world
+         * latency varies by approx. +/- 50 frames (at 96KHz) each time the
+         * stream is (re)started. When skipping packets 16 at endpoint start
+         * up, the real world latency is stable within +/- 1 frame (also
+         * across power cycles).
+         */
+        if (ep->chip->usb_id == USB_ID(0x0763, 0x2030) &&
+            ep->type == SND_USB_ENDPOINT_TYPE_DATA)
+                ep->skip_packets = 16;
 }
 
 void snd_usb_ctl_msg_quirk(struct usb_device *dev, unsigned int pipe,