usb: dwc3: ep0: implement support for Set Isoch Delay request

This is basically a noop for DWC3. We don't have
to do anything. Basically we test if the request
parameters are correct, cache the Isochronous
Delay and return success.
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/core.h

@@ -575,6 +575,7 @@ struct dwc3_request {
  * @setup_packet_pending: true when there's a Setup Packet in FIFO. Workaround
  * @needs_fifo_resize: not all users might want fifo resizing, flag it
  * @resize_fifos: tells us it's ok to reconfigure our TxFIFO sizes.
+ * @isoch_delay: wValue from Set Isochronous Delay request;
  * @u2sel: parameter from Set SEL request.
  * @u2pel: parameter from Set SEL request.
  * @u1sel: parameter from Set SEL request.
@@ -645,6 +646,7 @@ struct dwc3 {
 	enum dwc3_link_state	link_state;
 	enum dwc3_device_state	dev_state;
 
+	u16			isoch_delay;
 	u16			u2sel;
 	u16			u2pel;
 	u8			u1sel;

drivers/usb/dwc3/ep0.c

@@ -569,6 +569,28 @@ static int dwc3_ep0_set_sel(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
 	return __dwc3_gadget_ep0_queue(dep, &dwc->ep0_usb_req);
 }
 
+static int dwc3_ep0_set_isoch_delay(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
+{
+	u16		wLength;
+	u16		wValue;
+	u16		wIndex;
+
+	wValue = le16_to_cpu(ctrl->wValue);
+	wLength = le16_to_cpu(ctrl->wLength);
+	wIndex = le16_to_cpu(ctrl->wIndex);
+
+	if (wIndex || wLength)
+		return -EINVAL;
+
+	/*
+	 * REVISIT It's unclear from Databook what to do with this
+	 * value. For now, just cache it.
+	 */
+	dwc->isoch_delay = wValue;
+
+	return 0;
+}
+
 static int dwc3_ep0_std_request(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
 {
 	int ret;
@@ -598,6 +620,10 @@ static int dwc3_ep0_std_request(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
 		dev_vdbg(dwc->dev, "USB_REQ_SET_SEL\n");
 		ret = dwc3_ep0_set_sel(dwc, ctrl);
 		break;
+	case USB_REQ_SET_ISOCH_DELAY:
+		dev_vdbg(dwc->dev, "USB_REQ_SET_ISOCH_DELAY\n");
+		ret = dwc3_ep0_set_isoch_delay(dwc, ctrl);
+		break;
 	default:
 		dev_vdbg(dwc->dev, "Forwarding to gadget driver\n");
 		ret = dwc3_ep0_delegate_req(dwc, ctrl);