iio: adc: stm32-adc: fix sleep in atomic context

static void stm32_adc_dma_buffer_done(void *data)

{

	struct iio_dev *indio_dev = data;

	struct stm32_adc *adc = iio_priv(indio_dev);

	int residue = stm32_adc_dma_residue(adc);

	/*

	 * In DMA mode the trigger services of IIO are not used

	 * (e.g. no call to iio_trigger_poll).

	 * Calling irq handler associated to the hardware trigger is not

	 * relevant as the conversions have already been done. Data

	 * transfers are performed directly in DMA callback instead.

	 * This implementation avoids to call trigger irq handler that

	 * may sleep, in an atomic context (DMA irq handler context).

	 */

	dev_dbg(&indio_dev->dev, "%s bufi=%d\n", __func__, adc->bufi);

	while (residue >= indio_dev->scan_bytes) {

		u16 *buffer = (u16 *)&adc->rx_buf[adc->bufi];

	iio_trigger_poll_chained(indio_dev->trig);

		iio_push_to_buffers(indio_dev, buffer);

		residue -= indio_dev->scan_bytes;

		adc->bufi += indio_dev->scan_bytes;

		if (adc->bufi >= adc->rx_buf_sz)

			adc->bufi = 0;

	}

}

static int stm32_adc_dma_start(struct iio_dev *indio_dev)

{

	struct iio_dev *indio_dev;

	struct device *dev = &pdev->dev;

	irqreturn_t (*handler)(int irq, void *p) = NULL;

	struct stm32_adc *adc;

	int ret;

	if (ret < 0)

		return ret;

	if (!adc->dma_chan)

		handler = &stm32_adc_trigger_handler;

	ret = iio_triggered_buffer_setup(indio_dev,

					 &iio_pollfunc_store_time,

					 &stm32_adc_trigger_handler,

					 &iio_pollfunc_store_time, handler,

					 &stm32_adc_buffer_setup_ops);

	if (ret) {

		dev_err(&pdev->dev, "buffer setup failed\n");