usb: dwc3: gadget: check if dep->frame_number is still valid

Gadget driver may take an unbounded amount of time to queue requests
after XferNotReady. This is important for isochronous endpoints which
need to be started for a specific (micro-)frame.

If we fail to start a transfer for isochronous endpoint, let's try
queueing to a future interval and see if that helps. We will stop trying
if we fail a start transfer for 5 intervals in the future.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/core.h

@@ -37,6 +37,7 @@
 #define DWC3_EP0_SETUP_SIZE	512
 #define DWC3_ENDPOINTS_NUM	32
 #define DWC3_XHCI_RESOURCES_NUM	2
+#define DWC3_ISOC_MAX_RETRIES	5
 
 #define DWC3_SCRATCHBUF_SIZE	4096	/* each buffer is assumed to be 4KiB */
 #define DWC3_EVENT_BUFFERS_SIZE	4096

drivers/usb/dwc3/gadget.c

@@ -27,7 +27,7 @@
 #include "gadget.h"
 #include "io.h"
 
-#define DWC3_ALIGN_FRAME(d)	(((d)->frame_number + (d)->interval) \
+#define DWC3_ALIGN_FRAME(d, n)	(((d)->frame_number + ((d)->interval * (n))) \
 					& ~((d)->interval - 1))
 
 /**
@@ -1384,6 +1384,8 @@ static int dwc3_gadget_start_isoc_quirk(struct dwc3_ep *dep)
 static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
 {
 	struct dwc3 *dwc = dep->dwc;
+	int ret;
+	int i;
 
 	if (list_empty(&dep->pending_list)) {
 		dep->flags |= DWC3_EP_PENDING_REQUEST;
@@ -1400,8 +1402,15 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
 			return dwc3_gadget_start_isoc_quirk(dep);
 	}
 
-	dep->frame_number = DWC3_ALIGN_FRAME(dep);
-	return __dwc3_gadget_kick_transfer(dep);
+	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
+		dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
+
+		ret = __dwc3_gadget_kick_transfer(dep);
+		if (ret != -EAGAIN)
+			break;
+	}
+
+	return ret;
 }
 
 static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)