[PATCH 5/5] iio: adc: ad7380: use spi_optimize_message()

[David Lechner <dlechner@baylibre.com>]

This modifies the ad7380 ADC driver to use spi_optimize_message() to
optimize the SPI message for the buffered read operation. Since buffered
reads reuse the same SPI message for each read, this can improve
performance by reducing the overhead of setting up some parts the SPI
message in each spi_sync() call.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 drivers/iio/adc/ad7380.c | 52 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 45 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c
index abd746aef868..5c5d2642a474 100644
--- a/drivers/iio/adc/ad7380.c
+++ b/drivers/iio/adc/ad7380.c
@@ -133,6 +133,7 @@ struct ad7380_state {
 	struct spi_device *spi;
 	struct regulator *vref;
 	struct regmap *regmap;
+	struct spi_message *msg;
 	/*
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache lines.
@@ -231,19 +232,55 @@ static int ad7380_debugfs_reg_access(struct iio_dev *indio_dev, u32 reg,
 	return ret;
 }
 
+static int ad7380_buffer_preenable(struct iio_dev *indio_dev)
+{
+	struct ad7380_state *st = iio_priv(indio_dev);
+	struct spi_transfer *xfer;
+	int ret;
+
+	st->msg = spi_message_alloc(1, GFP_KERNEL);
+	if (!st->msg)
+		return -ENOMEM;
+
+	xfer = list_first_entry(&st->msg->transfers, struct spi_transfer,
+				transfer_list);
+
+	xfer->bits_per_word = st->chip_info->channels[0].scan_type.realbits;
+	xfer->len = 4;
+	xfer->rx_buf = st->scan_data.raw;
+
+	ret = spi_optimize_message(st->spi, st->msg);
+	if (ret) {
+		spi_message_free(st->msg);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int ad7380_buffer_postdisable(struct iio_dev *indio_dev)
+{
+	struct ad7380_state *st = iio_priv(indio_dev);
+
+	spi_unoptimize_message(st->msg);
+	spi_message_free(st->msg);
+
+	return 0;
+}
+
+static const struct iio_buffer_setup_ops ad7380_buffer_setup_ops = {
+	.preenable = ad7380_buffer_preenable,
+	.postdisable = ad7380_buffer_postdisable,
+};
+
 static irqreturn_t ad7380_trigger_handler(int irq, void *p)
 {
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct ad7380_state *st = iio_priv(indio_dev);
-	struct spi_transfer xfer = {
-		.bits_per_word = st->chip_info->channels[0].scan_type.realbits,
-		.len = 4,
-		.rx_buf = st->scan_data.raw,
-	};
 	int ret;
 
-	ret = spi_sync_transfer(st->spi, &xfer, 1);
+	ret = spi_sync(st->spi, st->msg);
 	if (ret)
 		goto out;
 
@@ -420,7 +457,8 @@ static int ad7380_probe(struct spi_device *spi)
 
 	ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev,
 					      iio_pollfunc_store_time,
-					      ad7380_trigger_handler, NULL);
+					      ad7380_trigger_handler,
+					      &ad7380_buffer_setup_ops);
 	if (ret)
 		return ret;
 

-- 
2.43.0