iio: adc: ad7768-1: Use new spi-engine implementation

Add  support for new spi-engine implementation on ad7768-1 driver.
This optimizes the offload transfers by reducing the CS delay and
removing the number of commands on offload's FIFO, which makes
the low latency mode viable.

Without the otimization there's not enough time between the end of a
transfer and the start of the next one, reducing the actual sample rate.

Signed-off-by: jonathanns <Jonathan.Santos@analog.com>

Author: jonathanns

drivers/iio/adc/ad7768-1.c

@@ -4,6 +4,7 @@
  *
  * Copyright 2017 Analog Devices Inc.
  */
+#include "linux/byteorder/little_endian.h"
 #include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
@@ -20,7 +21,7 @@
 #include <linux/regulator/consumer.h>
 #include <linux/sysfs.h>
 #include <linux/spi/spi.h>
-#include <linux/spi/spi-engine.h>
+#include <linux/spi/spi-engine-ex.h>
 #include <linux/util_macros.h>
 #include <linux/units.h>
 #include <linux/rational.h>
@@ -444,7 +445,7 @@ struct ad7768_state {
 	 */
 	union {
 		unsigned char buf[6];
-		__be32 word;
+		__le32 word;
 		struct {
 			__be32 chan;
 			s64 timestamp;
@@ -458,16 +459,16 @@ static int ad7768_spi_reg_read(struct ad7768_state *st, unsigned int addr,
 	struct spi_transfer xfer = {
 		.rx_buf = st->data.buf,
 		.len = len + 1,
-		.bits_per_word = (len == 3 ? 32 : 16),
 	};
 	unsigned char tx_data[4];
 	int ret;
+
 	tx_data[0] = AD7768_RD_FLAG_MSK(addr);
 	xfer.tx_buf = tx_data;
 	ret = spi_sync_transfer(st->spi, &xfer, 1);
 	if (ret < 0)
 		return ret;
-	*data = (len == 1 ? st->data.buf[0] : st->data.word);
+	*data = (len == 1 ? st->data.buf[1] : cpu_to_be32(st->data.word));
 	return ret;
 }
 
@@ -478,7 +479,6 @@ static int ad7768_spi_reg_write(struct ad7768_state *st,
 	struct spi_transfer xfer = {
 		.rx_buf = st->data.buf,
 		.len = 2,
-		.bits_per_word = 16,
 	};
 	unsigned char tx_data[2];
 	tx_data[0] = AD7768_WR_FLAG_MSK(addr);
@@ -1214,12 +1214,16 @@ static int ad7768_buffer_postenable(struct iio_dev *indio_dev)
 		st->offload_xfer.rx_buf = rx_data;
 		spi_message_init_with_transfers(&st->offload_msg, &st->offload_xfer, 1);
 
+		ret = spi_optimize_message(st->spi, &st->offload_msg);
+		if (ret < 0)
+			return ret;
+
 		spi_bus_lock(st->spi->master);
 
-		ret = spi_engine_offload_load_msg(st->spi, &st->offload_msg);
+		ret = spi_engine_ex_offload_load_msg(st->spi, &st->offload_msg);
 		if (ret < 0)
 			return ret;
-		spi_engine_offload_enable(st->spi, true);
+		spi_engine_ex_offload_enable(st->spi, true);
 	}
 
 	return ret;
@@ -1231,9 +1235,10 @@ static int ad7768_buffer_predisable(struct iio_dev *indio_dev)
 	unsigned int regval;
 
 	if (st->spi_is_dma_mapped) {
-		spi_engine_offload_enable(st->spi, false);
+		spi_engine_ex_offload_enable(st->spi, false);
 		spi_bus_unlock(st->spi->master);
 	}
+	spi_unoptimize_message(&st->offload_msg);
 
 	/*
 	 * To exit continuous read mode, perform a single read of the ADC_DATA
@@ -1445,7 +1450,7 @@ static int ad7768_probe(struct spi_device *spi)
 		return PTR_ERR(st->mclk);
 
 	st->mclk_freq = clk_get_rate(st->mclk);
-	st->spi_is_dma_mapped = spi_engine_offload_supported(spi);
+	st->spi_is_dma_mapped = spi_engine_ex_offload_supported(spi);
 	st->irq = spi->irq;
 	st->vref = regulator_get_voltage(st->regulator);