iio: adc: ad7124: Enable internal reference

When the internal reference was selected by a channel it was not enabled.
This patch fixes that and enables it.

Fixes: b3af341b ("iio: adc: Add ad7124 support")
Signed-off-by: Mircea Caprioru <mircea.caprioru@analog.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7124.c

@@ -39,6 +39,8 @@
 #define AD7124_STATUS_POR_FLAG_MSK	BIT(4)
 
 /* AD7124_ADC_CONTROL */
+#define AD7124_ADC_CTRL_REF_EN_MSK	BIT(8)
+#define AD7124_ADC_CTRL_REF_EN(x)	FIELD_PREP(AD7124_ADC_CTRL_REF_EN_MSK, x)
 #define AD7124_ADC_CTRL_PWR_MSK	GENMASK(7, 6)
 #define AD7124_ADC_CTRL_PWR(x)		FIELD_PREP(AD7124_ADC_CTRL_PWR_MSK, x)
 #define AD7124_ADC_CTRL_MODE_MSK	GENMASK(5, 2)
@@ -424,7 +426,10 @@ static int ad7124_init_channel_vref(struct ad7124_state *st,
 		break;
 	case AD7124_INT_REF:
 		st->channel_config[channel_number].vref_mv = 2500;
-		break;
+		st->adc_control &= ~AD7124_ADC_CTRL_REF_EN_MSK;
+		st->adc_control |= AD7124_ADC_CTRL_REF_EN(1);
+		return ad_sd_write_reg(&st->sd, AD7124_ADC_CONTROL,
+				      2, st->adc_control);
 	default:
 		dev_err(&st->sd.spi->dev, "Invalid reference %d\n", refsel);
 		return -EINVAL;