iio: adc: ad7768-1: fix MOSI idle state

All supported parts require that the MOSI line stays high
while in idle.

Fixes: 8a15c73 ("iio: adc: Add AD7768-1 ADC basic support")
Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>

Author: jonathanns

drivers/iio/adc/ad7768-1.c

@@ -890,6 +890,15 @@ static int ad7768_probe(struct spi_device *spi)
 		return -ENOMEM;
 
 	st = iio_priv(indio_dev);
+	/*
+	 * The ADC SDI line must be kept high when
+	 * data is not being clocked out of the controller.
+	 * Request the SPI controller to make MOSI idle high.
+	 */
+	spi->mode |= SPI_MOSI_IDLE_HIGH;
+	ret = spi_setup(spi);
+	if (ret < 0)
+		return ret;
 	st->spi = spi;
 
 	st->vref = devm_regulator_get(&spi->dev, "vref");