diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index b648b1ab9559..d67033a008e5 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -78,10 +78,30 @@ struct ad7949_adc_chip {
 	enum ad7949_ref_sel ref_sel;
 	u8 resolution;
 	u16 cfg;
+	u8 bits_per_word;
 	unsigned int current_channel;
-	u32 buffer ____cacheline_aligned;
+	union {
+		u32 buffer;
+		u16 buf16[2];
+		u8 buf8[4];
+	} ____cacheline_aligned;
 };
 
+static void ad7949_set_bits_per_word(struct ad7949_adc_chip *ad7949_adc)
+{
+	/* Prefer messages that match the ADC's resolution */
+	if (ad7949_adc->spi->controller->bits_per_word_mask &
+			SPI_BPW_MASK(ad7949_adc->resolution))
+		ad7949_adc->bits_per_word = ad7949_adc->resolution;
+	/* Second choice is to pad 14-bit words to 16 */
+	else if (ad7949_adc->spi->controller->bits_per_word_mask &
+			SPI_BPW_MASK(16))
+		ad7949_adc->bits_per_word = 16;
+	/* Last resort, use 8-bit words */
+	else
+		ad7949_adc->bits_per_word = 8;
+}
+
 static bool ad7949_spi_cfg_is_read_back(struct ad7949_adc_chip *ad7949_adc)
 {
 	if (!(ad7949_adc->cfg & AD7949_CFG_READBACK))
@@ -90,39 +110,63 @@ static bool ad7949_spi_cfg_is_read_back(struct ad7949_adc_chip *ad7949_adc)
 	return false;
 }
 
-static int ad7949_spi_bits_per_word(struct ad7949_adc_chip *ad7949_adc)
+static int ad7949_message_len(struct ad7949_adc_chip *ad7949_adc)
 {
-	int ret = ad7949_adc->resolution;
+	int tx_len = 2;
 
 	if (ad7949_spi_cfg_is_read_back(ad7949_adc))
-		ret += AD7949_CFG_REG_SIZE_BITS;
+		tx_len += 2;
 
-	return ret;
+	return tx_len;
 }
 
 static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
 				u16 mask)
 {
-	int ret;
-	int bits_per_word = ad7949_spi_bits_per_word(ad7949_adc);
-	int shift = bits_per_word - AD7949_CFG_REG_SIZE_BITS;
+	int ret = 0;
+	u16 tmp_cfg = 0;
 	struct spi_message msg;
 	struct spi_transfer tx[] = {
 		{
 			.tx_buf = &ad7949_adc->buffer,
-			.len = 4,
-			.bits_per_word = bits_per_word,
-		},
+			.len = ad7949_message_len(ad7949_adc),
+			.bits_per_word = ad7949_adc->bits_per_word,
+		}
 	};
 
-	ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
-	ad7949_adc->buffer = (ad7949_adc->cfg & AD7949_CFG_MASK_TOTAL) << shift;
+	ad7949_adc->buffer = 0;
+
+	tmp_cfg = ((val & mask) | (ad7949_adc->cfg & ~mask)) &
+		AD7949_CFG_MASK_TOTAL;
+
+	/* If no change, return */
+	if (tmp_cfg == ad7949_adc->cfg)
+		return 0;
+
+	ad7949_adc->cfg = tmp_cfg;
+
+	switch (ad7949_adc->bits_per_word) {
+	case 16:
+		ad7949_adc->buf16[0] = ad7949_adc->cfg << 2;
+		break;
+	case 14:
+		ad7949_adc->buf16[0] = ad7949_adc->cfg;
+		break;
+	default: /* 8 */
+		/* Pack 14-bit value into 2 bytes, MSB first */
+		ad7949_adc->buf8[0] = FIELD_GET(GENMASK(13, 6), ad7949_adc->cfg);
+		ad7949_adc->buf8[1] = FIELD_GET(GENMASK(5, 0), ad7949_adc->cfg);
+		ad7949_adc->buf8[1] = ad7949_adc->buf8[1] << 2;
+		break;
+	}
+
 	spi_message_init_with_transfers(&msg, tx, 1);
+
 	ret = spi_sync(ad7949_adc->spi, &msg);
 
 	/*
-	 * This delay is to avoid a new request before the required time to
-	 * send a new command to the device
+	 * This delay is to avoid a new request before the required
+	 * time to send a new command to the device
 	 */
 	udelay(2);
 
@@ -149,17 +193,17 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
 				   unsigned int channel)
 {
 	int ret;
-	int bits_per_word = ad7949_spi_bits_per_word(ad7949_adc);
-	int mask = GENMASK(ad7949_adc->resolution, 0);
 	struct spi_message msg;
 	struct spi_transfer tx[] = {
 		{
 			.rx_buf = &ad7949_adc->buffer,
-			.len = 4,
-			.bits_per_word = bits_per_word,
-		},
+			.len = ad7949_message_len(ad7949_adc),
+			.bits_per_word = ad7949_adc->bits_per_word,
+		}
 	};
 
+	ad7949_adc->current_channel = channel;
+
 	ret = ad7949_spi_write_cfg(ad7949_adc,
 				   FIELD_PREP(AD7949_CFG_CHAN_SEL, channel),
 				   AD7949_CFG_CHAN_SEL);
@@ -167,23 +211,37 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
 		return ret;
 
 	ad7949_adc->buffer = 0;
+
 	spi_message_init_with_transfers(&msg, tx, 1);
+
 	ret = spi_sync(ad7949_adc->spi, &msg);
 	if (ret)
 		return ret;
 
 	/*
-	 * This delay is to avoid a new request before the required time to
-	 * send a new command to the device
+	 * This delay is to avoid a new request before the required time
+	 * to send a new command to the device.
 	 */
 	udelay(2);
 
-	ad7949_adc->current_channel = channel;
-
-	if (ad7949_spi_cfg_is_read_back(ad7949_adc))
-		*val = (ad7949_adc->buffer >> AD7949_CFG_REG_SIZE_BITS) & mask;
-	else
-		*val = ad7949_adc->buffer & mask;
+	switch (ad7949_adc->bits_per_word) {
+	case 16:
+		*val = ad7949_adc->buf16[0];
+		/* Shift-out padding bits */
+		if (ad7949_adc->resolution == 14)
+			*val = *val >> 2;
+		break;
+	case 14:
+		*val = ad7949_adc->buf16[0] & GENMASK(13, 0);
+		break;
+	default: /* 8 */
+		/* Convert byte array to u16, MSB first */
+		*val = (ad7949_adc->buf8[0] << 8) | ad7949_adc->buf8[1];
+		/* Shift-out padding bits */
+		if (ad7949_adc->resolution == 14)
+			*val = *val >> 2;
+		break;
+	}
 
 	return 0;
 }
@@ -334,6 +392,7 @@ static int ad7949_spi_probe(struct spi_device *spi)
 	spec = &ad7949_adc_spec[spi_get_device_id(spi)->driver_data];
 	indio_dev->num_channels = spec->num_channels;
 	ad7949_adc->resolution = spec->resolution;
+	ad7949_set_bits_per_word(ad7949_adc);
 
 	ret = of_property_read_u32(ad7949_adc->indio_dev->dev.of_node,
 			"adi,reference-select",
