dwc_otg: make nak_holdoff work as intended with empty queues

If URBs reading from non-periodic split endpoints were dequeued and
the last transfer from the endpoint was a NAK handshake, the resulting
qh->nak_frame value was stale which would result in unnecessarily long
polling intervals for the first subsequent transfer with a fresh URB.

Fixup qh->nak_frame in dwc_otg_hcd_urb_dequeue and also guard against
a case where a single URB is submitted to the endpoint, a NAK was
received on the transfer immediately prior to receiving data and the
device subsequently resubmits another URB past the qh->nak_frame interval.

Fixes #1709

drivers/usb/host/dwc_otg/dwc_otg_hcd.c

@@ -616,7 +616,7 @@ int dwc_otg_hcd_urb_dequeue(dwc_otg_hcd_t * hcd,
 			if (fiq_fsm_enable && (hcd->fiq_state->channel[n].fsm != FIQ_PASSTHROUGH)) {
 				qh->channel->halt_status = DWC_OTG_HC_XFER_URB_DEQUEUE;
 				qh->channel->halt_pending = 1;
-				hcd->fiq_state->channel[n].fsm = FIQ_DEQUEUE_ISSUED;
+				//hcd->fiq_state->channel[n].fsm = FIQ_DEQUEUE_ISSUED;
 			} else {
 				dwc_otg_hc_halt(hcd->core_if, qh->channel,
 						DWC_OTG_HC_XFER_URB_DEQUEUE);
@@ -634,6 +634,8 @@ int dwc_otg_hcd_urb_dequeue(dwc_otg_hcd_t * hcd,
                     hcd->core_if->dma_desc_enable?"DMA ":"");
 	if (!hcd->core_if->dma_desc_enable) {
 		uint8_t b = urb_qtd->in_process;
+		if (nak_holdoff && qh->do_split && dwc_qh_is_non_per(qh))
+			qh->nak_frame = 0xFFFF;
 		dwc_otg_hcd_qtd_remove_and_free(hcd, urb_qtd, qh);
 		if (b) {
 			dwc_otg_hcd_qh_deactivate(hcd, qh, 0);

drivers/usb/host/dwc_otg/dwc_otg_hcd_intr.c

@@ -2382,15 +2382,17 @@ void dwc_otg_hcd_handle_hc_fsm(dwc_otg_hcd_t *hcd, uint32_t num)
 	fiq_print(FIQDBG_INT, hcd->fiq_state, "OUT %01d %01d ", num , st->fsm);
 
 	hostchannels = hcd->available_host_channels;
+	if (hc->halt_pending) {
+		/* Dequeue: The FIQ was allowed to complete the transfer but state has been cleared. */
+		release_channel(hcd, hc, NULL, hc->halt_status);
+		return;
+	}
 	switch (st->fsm) {
 	case FIQ_TEST:
 		break;
 
 	case FIQ_DEQUEUE_ISSUED:
-		/* hc_halt was called. QTD no longer exists. */
-		/* TODO: for a nonperiodic split transaction, need to issue a
-		 * CLEAR_TT_BUFFER hub command if we were in the start-split phase.
-		 */
+		/* Handled above, but keep for posterity */
 		release_channel(hcd, hc, NULL, hc->halt_status);
 		break;
 

drivers/usb/host/dwc_otg/dwc_otg_hcd_queue.c

@@ -793,6 +793,10 @@ void dwc_otg_hcd_qh_deactivate(dwc_otg_hcd_t * hcd, dwc_otg_qh_t * qh,
 			/* Add back to inactive non-periodic schedule. */
 			dwc_otg_hcd_qh_add(hcd, qh);
 			//hcd->fiq_state->kick_np_queues = 1;
+		} else {
+			if(nak_holdoff && qh->do_split) {
+				qh->nak_frame = 0xFFFF;
+			}
 		}
 	} else {
 		uint16_t frame_number = dwc_otg_hcd_get_frame_number(hcd);