[ALSA] usb-audio - fix synchronization packet interval with Audigy 2 NX

USB generic driver
When a device does not provide the bRefresh field in its audio endpoint
descriptors, use the bInterval field instead.

Furthermore, increase the number of sync URBs for better queueing.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 076da19a9e282ff6c8dc415c9e68df57d74c34f3..a82412b8790de2f4f0322ca9c6e334e09e5af8df 100644 (file)
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -98,7 +98,7 @@ MODULE_PARM_DESC(async_unlink, "Use async unlink mode.");
 #define MAX_PACKS      10
 #define MAX_PACKS_HS   (MAX_PACKS * 8) /* in high speed mode */
 #define MAX_URBS       5       /* max. 20ms long packets */
-#define SYNC_URBS      2       /* always two urbs for sync */
+#define SYNC_URBS      4       /* always four urbs for sync */
 #define MIN_PACKS_URB  1       /* minimum 1 packet per urb */
 
 typedef struct snd_usb_substream snd_usb_substream_t;
@@ -1240,8 +1240,13 @@ static int set_format(snd_usb_substream_t *subs, struct audioformat *fmt)
                    get_endpoint(alts, 1)->bRefresh >= 1 &&
                    get_endpoint(alts, 1)->bRefresh <= 9)
                        subs->syncinterval = get_endpoint(alts, 1)->bRefresh;
-               else
+               else if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
                        subs->syncinterval = 1;
+               else if (get_endpoint(alts, 1)->bInterval >= 1 &&
+                        get_endpoint(alts, 1)->bInterval <= 16)
+                       subs->syncinterval = get_endpoint(alts, 1)->bInterval - 1;
+               else
+                       subs->syncinterval = 3;
        }
 
        /* always fill max packet size */