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: Jonathan Santos <Jonathan.Santos@analog.com>

Author: jonathanns

drivers/iio/adc/ad7768-1.c

@@ -21,7 +21,7 @@
 #include <linux/sysfs.h>
 #include "linux/util_macros.h"
 #include <linux/spi/spi.h>
-#include <linux/spi/spi-engine.h>
+#include <linux/spi/spi-engine-ex.h>
 
 #include <linux/iio/buffer.h>
 #include <linux/iio/buffer-dma.h>
@@ -300,6 +300,8 @@ struct ad7768_state {
 	struct mutex lock;
 	struct clk *mclk;
 	struct gpio_chip gpiochip;
+	struct spi_transfer offload_xfer;
+	struct spi_message offload_msg;
 	unsigned int gpio_avail_map;
 	unsigned int mclk_freq;
 	unsigned int samp_freq;
@@ -341,7 +343,7 @@ static int ad7768_spi_reg_read(struct ad7768_state *st, unsigned int addr,
 	unsigned char tx_data[4];
 	int ret;
 
-	tx_data[0] = AD7768_RD_FLAG_MSK(addr);
+	tx_data[len] = AD7768_RD_FLAG_MSK(addr);
 	xfer.tx_buf = tx_data;
 	ret = spi_sync_transfer(st->spi, &xfer, 1);
 	if (ret < 0)
@@ -362,8 +364,8 @@ static int ad7768_spi_reg_write(struct ad7768_state *st,
 	};
 	unsigned char tx_data[2];
 
-	tx_data[0] = AD7768_WR_FLAG_MSK(addr);
-	tx_data[1] = val & 0xFF;
+	tx_data[1] = AD7768_WR_FLAG_MSK(addr);
+	tx_data[0] = val & 0xFF;
 	xfer.tx_buf = tx_data;
 	return spi_sync_transfer(st->spi, &xfer, 1);
 }
@@ -1040,19 +1042,16 @@ static irqreturn_t ad7768_interrupt(int irq, void *dev_id)
 static int ad7768_buffer_postenable(struct iio_dev *indio_dev)
 {
 	struct ad7768_state *st = iio_priv(indio_dev);
-	struct spi_transfer xfer = {
-		.len = 1,
-	};
 	unsigned int rx_data[2];
-	struct spi_message msg;
 	const struct iio_scan_type *scan_type;
 	int ret;
 
 	scan_type = iio_get_current_scan_type(indio_dev, &indio_dev->channels[0]);
 	if (IS_ERR(scan_type))
 		return PTR_ERR(scan_type);
 
-	xfer.bits_per_word = scan_type->realbits;
+	st->offload_xfer.len = roundup_pow_of_two(BITS_TO_BYTES(scan_type->realbits));
+	st->offload_xfer.bits_per_word = scan_type->realbits;
 
 	/*
 	* Write a 1 to the LSB of the INTERFACE_FORMAT register to enter
@@ -1064,14 +1063,19 @@ static int ad7768_buffer_postenable(struct iio_dev *indio_dev)
 		return ret;
 
 	if (st->spi_is_dma_mapped) {
+		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);
 
-		xfer.rx_buf = rx_data;
-		spi_message_init_with_transfers(&msg, &xfer, 1);
-		ret = spi_engine_offload_load_msg(st->spi, &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;
@@ -1083,9 +1087,10 @@ 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
@@ -1219,7 +1224,7 @@ 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;
 
 	mutex_init(&st->lock);