[PATCH v2 6/6] iio: adc: ad7380: Add support for multiple SPI buses

[David Lechner <dlechner@baylibre.com>]

Add support for multiple SPI buses to increase throughput. The AD7380
family of ADCs have multiple SDO lines on the chip that can be used to
read each channel on a separate SPI bus. If wired up to a SPI controller
that supports it, the driver will now take advantage of this feature.
This allows reaching the maximum sample rate advertised in the datasheet
when combined with SPI offloading.

Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
---

v2 changes:
* Move st->seq_xfer[3].multi_bus_mode = SPI_MULTI_BUS_MODE_STRIPE;
  to probe().
---
 drivers/iio/adc/ad7380.c | 42 +++++++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c
index bfd908deefc0f40b42bd8a44bfce7a2510b2fdf1..8891c31e61714b00fb01571f7ddd163cc948a8fb 100644
--- a/drivers/iio/adc/ad7380.c
+++ b/drivers/iio/adc/ad7380.c
@@ -77,8 +77,7 @@
 #define AD7380_CONFIG1_REFSEL		BIT(1)
 #define AD7380_CONFIG1_PMODE		BIT(0)
 
-#define AD7380_CONFIG2_SDO2		GENMASK(9, 8)
-#define AD7380_CONFIG2_SDO		BIT(8)
+#define AD7380_CONFIG2_SDO		GENMASK(9, 8)
 #define AD7380_CONFIG2_RESET		GENMASK(7, 0)
 
 #define AD7380_CONFIG2_RESET_SOFT	0x3C
@@ -92,11 +91,6 @@
 #define T_CONVERT_X_NS 500		/* xth conversion start time (oversampling) */
 #define T_POWERUP_US 5000		/* Power up */
 
-/*
- * AD738x support several SDO lines to increase throughput, but driver currently
- * supports only 1 SDO line (standard SPI transaction)
- */
-#define AD7380_NUM_SDO_LINES		1
 #define AD7380_DEFAULT_GAIN_MILLI	1000
 
 /*
@@ -1084,7 +1078,7 @@ static int ad7380_set_ch(struct ad7380_state *st, unsigned int ch)
 	if (oversampling_ratio > 1)
 		xfer.delay.value = T_CONVERT_0_NS +
 			T_CONVERT_X_NS * (oversampling_ratio - 1) *
-			st->chip_info->num_simult_channels / AD7380_NUM_SDO_LINES;
+			st->chip_info->num_simult_channels / st->spi->num_data_bus;
 
 	return spi_sync_transfer(st->spi, &xfer, 1);
 }
@@ -1113,7 +1107,7 @@ static int ad7380_update_xfers(struct ad7380_state *st,
 	if (oversampling_ratio > 1)
 		t_convert = T_CONVERT_0_NS + T_CONVERT_X_NS *
 			(oversampling_ratio - 1) *
-			st->chip_info->num_simult_channels / AD7380_NUM_SDO_LINES;
+			st->chip_info->num_simult_channels / st->spi->num_data_bus;
 
 	if (st->seq) {
 		xfer[0].delay.value = xfer[1].delay.value = t_convert;
@@ -1198,6 +1192,8 @@ static int ad7380_init_offload_msg(struct ad7380_state *st,
 	xfer->bits_per_word = scan_type->realbits;
 	xfer->offload_flags = SPI_OFFLOAD_XFER_RX_STREAM;
 	xfer->len = AD7380_SPI_BYTES(scan_type) * st->chip_info->num_simult_channels;
+	if (st->spi->num_data_bus > 1)
+		xfer->multi_bus_mode = SPI_MULTI_BUS_MODE_STRIPE;
 
 	spi_message_init_with_transfers(&st->offload_msg, xfer, 1);
 	st->offload_msg.offload = st->offload;
@@ -1793,6 +1789,7 @@ static const struct iio_info ad7380_info = {
 
 static int ad7380_init(struct ad7380_state *st, bool external_ref_en)
 {
+	u32 sdo;
 	int ret;
 
 	/* perform hard reset */
@@ -1815,11 +1812,24 @@ static int ad7380_init(struct ad7380_state *st, bool external_ref_en)
 	st->ch = 0;
 	st->seq = false;
 
-	/* SPI 1-wire mode */
+	/* SDO field has an irregular mapping. */
+	switch (st->spi->num_data_bus) {
+	case 1:
+		sdo = 1;
+		break;
+	case 2:
+		sdo = 0;
+		break;
+	case 4:
+		sdo = 2;
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	return regmap_update_bits(st->regmap, AD7380_REG_ADDR_CONFIG2,
 				  AD7380_CONFIG2_SDO,
-				  FIELD_PREP(AD7380_CONFIG2_SDO,
-					     AD7380_NUM_SDO_LINES));
+				  FIELD_PREP(AD7380_CONFIG2_SDO, sdo));
 }
 
 static int ad7380_probe_spi_offload(struct iio_dev *indio_dev,
@@ -1842,7 +1852,7 @@ static int ad7380_probe_spi_offload(struct iio_dev *indio_dev,
 				     "failed to get offload trigger\n");
 
 	sample_rate = st->chip_info->max_conversion_rate_hz *
-		      AD7380_NUM_SDO_LINES / st->chip_info->num_simult_channels;
+		      spi->num_data_bus / st->chip_info->num_simult_channels;
 
 	st->sample_freq_range[0] = 1; /* min */
 	st->sample_freq_range[1] = 1; /* step */
@@ -2010,6 +2020,8 @@ static int ad7380_probe(struct spi_device *spi)
 	st->normal_xfer[0].cs_change_delay.value = st->chip_info->timing_specs->t_csh_ns;
 	st->normal_xfer[0].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
 	st->normal_xfer[1].rx_buf = st->scan_data;
+	if (spi->num_data_bus > 1)
+		st->normal_xfer[1].multi_bus_mode = SPI_MULTI_BUS_MODE_STRIPE;
 
 	spi_message_init_with_transfers(&st->normal_msg, st->normal_xfer,
 					ARRAY_SIZE(st->normal_xfer));
@@ -2031,6 +2043,10 @@ static int ad7380_probe(struct spi_device *spi)
 	st->seq_xfer[2].cs_change = 1;
 	st->seq_xfer[2].cs_change_delay.value = st->chip_info->timing_specs->t_csh_ns;
 	st->seq_xfer[2].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
+	if (spi->num_data_bus > 1) {
+		st->seq_xfer[2].multi_bus_mode = SPI_MULTI_BUS_MODE_STRIPE;
+		st->seq_xfer[3].multi_bus_mode = SPI_MULTI_BUS_MODE_STRIPE;
+	}
 
 	spi_message_init_with_transfers(&st->seq_msg, st->seq_xfer,
 					ARRAY_SIZE(st->seq_xfer));

-- 
2.43.0