nrf5x: Handle ISOOUT CRC errors

NRF5x USB controller can detect ISO OUT CRC errors.
In such case USBEVENT is signaled with EVENTCAUSE_ISOOUTCRC set.
Even if controller detects corrupted ISO OUT packet it allows
to data transfer from ednpoint to RAM however packet is corrupted
and code could just as well drop packet altogether.

With current implementation incoming ISO OUT packets were put in
FIFO and exact information how much data already in FIFO is correct
was hard to keep track of.
If was observed that on certain configurations HS hub when FS device
was connected occasionally sent invalid (short) packet. In such case
if packet length was reported odd audio stream was not recognizable any
more.

With this change corrupted packets are not passed to upper layers
and are silently dropped.

Author: kasjer

src/portable/nordic/nrf5x/dcd_nrf5x.c

@@ -653,7 +653,11 @@ void dcd_int_handler(uint8_t rhport)
     if (NRF_USBD->EPOUTEN & USBD_EPOUTEN_ISOOUT_Msk)
     {
       iso_enabled = true;
-      xact_out_dma(EP_ISO_NUM);
+      // Transfer from endpoint to RAM only if data is not corrupted
+      if ((int_status & USBD_INTEN_USBEVENT_Msk) == 0 ||
+          (NRF_USBD->EVENTCAUSE & USBD_EVENTCAUSE_ISOOUTCRC_Msk) == 0) {
+        xact_out_dma(EP_ISO_NUM);
+      }
     }
 
     // ISOIN: Notify client that data was transferred
@@ -683,7 +687,7 @@ void dcd_int_handler(uint8_t rhport)
   {
     TU_LOG(2, "EVENTCAUSE = 0x%04lX\r\n", NRF_USBD->EVENTCAUSE);
 
-    enum { EVT_CAUSE_MASK = USBD_EVENTCAUSE_SUSPEND_Msk | USBD_EVENTCAUSE_RESUME_Msk | USBD_EVENTCAUSE_USBWUALLOWED_Msk };
+    enum { EVT_CAUSE_MASK = USBD_EVENTCAUSE_SUSPEND_Msk | USBD_EVENTCAUSE_RESUME_Msk | USBD_EVENTCAUSE_USBWUALLOWED_Msk | USBD_EVENTCAUSE_ISOOUTCRC_Msk };
     uint32_t const evt_cause = NRF_USBD->EVENTCAUSE & EVT_CAUSE_MASK;
     NRF_USBD->EVENTCAUSE = evt_cause; // clear interrupt