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Commit a93455e1 authored by Thomas Pugliese's avatar Thomas Pugliese Committed by Takashi Iwai
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ALSA: usb: use multiple packets per urb for Wireless USB inbound audio 



For Wireless USB audio devices, use multiple isoc packets per URB for
inbound endpoints with a datainterval < 5.  This allows the WUSB host
controller to take advantage of bursting to service endpoints whose
logical polling interval is less than the 4ms minimum polling interval
limit in WUSB.

Signed-off-by: default avatarThomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 2fd3f170

sound/usb/endpoint.c

+15 −1
Original line number Diff line number Diff line
@@ -636,8 +636,22 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep, 
	if (usb_pipein(ep->pipe) ||

			snd_usb_endpoint_implicit_feedback_sink(ep)) {



		urb_packs = packs_per_ms;

		/*

		 * Wireless devices can poll at a max rate of once per 4ms.

		 * For dataintervals less than 5, increase the packet count to

		 * allow the host controller to use bursting to fill in the

		 * gaps.

		 */

		if (snd_usb_get_speed(ep->chip->dev) == USB_SPEED_WIRELESS) {

			int interval = ep->datainterval;

			while (interval < 5) {

				urb_packs <<= 1;

				++interval;

			}

		}

		/* make capture URBs <= 1 ms and smaller than a period */

		urb_packs = min(max_packs_per_urb, packs_per_ms);

		urb_packs = min(max_packs_per_urb, urb_packs);

		while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)

			urb_packs >>= 1;

		ep->nurbs = MAX_URBS;