usbdev_synopsys_dwc2: Mask RX FIFO irq with DMA

When using DMA to transfer endpoint data from the RX FIFO to the
endpoint memory, the RXFLVL irq is not needed as that is already handled
by the DMA. Furthermore, servicing this irq anyway can cause the event
handling to interpret data from the FIFO as the endpoint and status
marker during the DMA transfer.

This commit masks the RXFLVL irq while DMA is used for the endpoint
transfers.

drivers/usbdev_synopsys_dwc2/usbdev_synopsys_dwc2.c

@@ -85,8 +85,7 @@
      USB_OTG_GINTMSK_USBRST   | \
      USB_OTG_GINTMSK_OTGINT   | \
      USB_OTG_GINTMSK_IEPINT   | \
-     USB_OTG_GINTMSK_OEPINT   | \
-     USB_OTG_GINTMSK_RXFLVLM)
+     USB_OTG_GINTMSK_OEPINT)
 
 #define DWC2_PKTSTS_GONAK          0x01    /**< Rx fifo global out nak */
 #define DWC2_PKTSTS_DATA_UPDT      0x02    /**< Rx fifo data update    */
@@ -855,9 +854,14 @@ static void _usbdev_init(usbdev_t *dev)
         _device_regs(conf)->DIEPMSK |= USB_OTG_DIEPMSK_XFRCM;
     }
 
+    uint32_t gint_mask = DWC2_FSHS_USB_GINT_MASK;
+    if (!_uses_dma(conf)) {
+        gint_mask |= USB_OTG_GINTMSK_RXFLVLM;
+    }
+
     /* Clear the interrupt flags and unmask those interrupts */
-    _global_regs(conf)->GINTSTS |= DWC2_FSHS_USB_GINT_MASK;
-    _global_regs(conf)->GINTMSK |= DWC2_FSHS_USB_GINT_MASK;
+    _global_regs(conf)->GINTSTS |= gint_mask;
+    _global_regs(conf)->GINTMSK |= gint_mask;
 
     DEBUG("usbdev: USB peripheral currently in %s mode\n",
           (_global_regs(
@@ -1277,7 +1281,7 @@ void _isr_common(dwc2_usb_otg_fshs_t *usbdev)
     uint32_t status = _global_regs(conf)->GINTSTS;
 
     if (status) {
-        if (status & USB_OTG_GINTSTS_RXFLVL) {
+        if ((status & USB_OTG_GINTSTS_RXFLVL) && !_uses_dma(conf)) {
             unsigned epnum = _global_regs(conf)->GRXSTSR &
                              USB_OTG_GRXSTSP_EPNUM_Msk;
             usbdev->usbdev.epcb(&usbdev->out[epnum].ep, USBDEV_EVENT_ESR);