[nrf fromtree] usb: device_next: uac2: Double buffering on data OUT endpoints

Enable double buffering on data OUT endpoints to allow USB stack to
enqueue next transfer as soon as possible. This is especially useful
when operating at High-Speed where there is significantly less time
between subsequent SOF packets.

Signed-off-by: Tomasz Moń <[email protected]>
(cherry picked from commit 2f343bf)

Author: tmon-nordic

subsys/usb/device_next/class/usbd_uac2.c

@@ -28,6 +28,7 @@ LOG_MODULE_REGISTER(usbd_uac2, CONFIG_USBD_UAC2_LOG_LEVEL);
 	IF_ENABLED(DT_NODE_HAS_COMPAT(node, zephyr_uac2_audio_streaming), (	\
 		+ AS_HAS_ISOCHRONOUS_DATA_ENDPOINT(node)			\
 		+ AS_IS_USB_ISO_IN(node) /* ISO IN double buffering */		\
+		+ AS_IS_USB_ISO_OUT(node) /* ISO OUT double buffering */	\
 		+ AS_HAS_EXPLICIT_FEEDBACK_ENDPOINT(node)))
 #define COUNT_UAC2_EP_BUFFERS(i)						\
 	+ DT_PROP(DT_DRV_INST(i), interrupt_endpoint)				\
@@ -348,6 +349,7 @@ static void schedule_iso_out_read(struct usbd_class_data *const c_data,
 	const struct uac2_cfg *cfg = dev->config;
 	struct uac2_ctx *ctx = dev->data;
 	struct net_buf *buf;
+	atomic_t *queued_bits = &ctx->as_queued;
 	void *data_buf;
 	int as_idx = terminal_to_as_interface(dev, terminal);
 	int ret;
@@ -364,16 +366,19 @@ static void schedule_iso_out_read(struct usbd_class_data *const c_data,
 		return;
 	}
 
-	if (atomic_test_and_set_bit(&ctx->as_queued, as_idx)) {
-		/* Transfer already queued - do not requeue */
-		return;
+	if (atomic_test_and_set_bit(queued_bits, as_idx)) {
+		queued_bits = &ctx->as_double;
+		if (atomic_test_and_set_bit(queued_bits, as_idx)) {
+			/* Transfer already double queued - nothing to do */
+			return;
+		}
 	}
 
 	/* Prepare transfer to read audio OUT data from host */
 	data_buf = ctx->ops->get_recv_buf(dev, terminal, mps, ctx->user_data);
 	if (!data_buf) {
 		LOG_ERR("No data buffer for terminal %d", terminal);
-		atomic_clear_bit(&ctx->as_queued, as_idx);
+		atomic_clear_bit(queued_bits, as_idx);
 		return;
 	}
 
@@ -386,15 +391,15 @@ static void schedule_iso_out_read(struct usbd_class_data *const c_data,
 		 */
 		ctx->ops->data_recv_cb(dev, terminal,
 				       data_buf, 0, ctx->user_data);
-		atomic_clear_bit(&ctx->as_queued, as_idx);
+		atomic_clear_bit(queued_bits, as_idx);
 		return;
 	}
 
 	ret = usbd_ep_enqueue(c_data, buf);
 	if (ret) {
 		LOG_ERR("Failed to enqueue net_buf for 0x%02x", ep);
 		net_buf_unref(buf);
-		atomic_clear_bit(&ctx->as_queued, as_idx);
+		atomic_clear_bit(queued_bits, as_idx);
 	}
 }
 
@@ -814,6 +819,10 @@ static int uac2_request(struct usbd_class_data *const c_data, struct net_buf *bu
 	if (USB_EP_DIR_IS_OUT(ep)) {
 		ctx->ops->data_recv_cb(dev, terminal, buf->__buf, buf->len,
 				       ctx->user_data);
+		if (buf->frags) {
+			ctx->ops->data_recv_cb(dev, terminal, buf->frags->__buf,
+					       buf->frags->len, ctx->user_data);
+		}
 	} else if (!is_feedback) {
 		ctx->ops->buf_release_cb(dev, terminal, buf->__buf, ctx->user_data);
 		if (buf->frags) {