DMA I2S callback not triggering at high frequency

Hello,

We are using the I2S library in order to read data from an ICS43432 with a SAMD21 in order to develop applications for ambient noise frequency analysis, within the [SmartCitizen](https://github.com/fablabbcn/smartcitizen-kit-20) project.

We are facing an issue within the library that halts the _I2S_ receive process, due to a `DMA.onTransferComplete(_dmaChannel, I2SClass::onDmaTransferComplete);` callback not being raised after a DMA transfer. This provokes the doubleBuffer system to never be updated since neither the `I2S.read(buffer, size)` nor the `I2S.onTransferComplete()` functions go through the process of rising another `DMA.transfer` and therefore not returning anything. Here is the code in question:

```
int I2SClass::read(void* buffer, size_t size)
{
if (_state != I2S_STATE_RECEIVER) {
enableReceiver();
}

uint8_t enableInterrupts = ((__get_PRIMASK() & 0x1) == 0);

// disable interrupts,
__disable_irq();

int read = _doubleBuffer.read(buffer, size);

if (_dmaTransferInProgress == false && _doubleBuffer.available() == 0) {
// no DMA transfer in progress, start a receive process
_dmaTransferInProgress = true;

DMA.transfer(_dmaChannel, i2sd.data(_deviceIndex), _doubleBuffer.data(), _doubleBuffer.availableForWrite());

// switch to the next buffer for user output (will be empty)
_doubleBuffer.swap();
}

if (enableInterrupts) {
// re-enable the interrupts
__enable_irq();
}

return read;

}
```

In case of `_dmaTransferInProgress == true`, due to a faulty DMA callback, the I2S.read() always returns zeroes since no buffer is available after emptying the allocated `_doubleBuffer`. This issue takes place normally at _high sampling rates_ (our use case is 44.1kHz) for the microphone and, from our point of view, randomly. We assume though that since the `DMA.onTransferComplete` is triggered by a DMA software trigger, the `i2sd.data()` itself shouldn't be the rootcause, but this is just an assumption out of our lack of expertise about the I2S and DMA interactions in depth.

--> Therefore, we wonder if this issue can be due to a DMA callback failure itself? Is there a way we can check if this is the case and/or try to find if the data is being still received from the I2S? We will try to provide some debugging data from _gdb_ if possible, since the issue is a bit tricky to catch.

**NB**: This was also raised after testing out the ArduinoSound library in this [issue](https://github.com/arduino-libraries/ArduinoSound/issues/3), although further analysis of the event lead us to this point.

Thank you in advance!