[PATCH v2 5/5] iio: adc: ad7380: use spi_optimize_message()

[David Lechner <dlechner@xxxxxxxxxxxx>]

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@xxxxxxxxxxxx>
---

v2 changes:
- Removed dynamic allocation of spi xfer/msg
- Moved spi message optimization to probe function
- Dropped buffer pre/post callbacks

 drivers/iio/adc/ad7380.c | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c
index abd746aef868..6b3fd20c8f1f 100644
--- a/drivers/iio/adc/ad7380.c
+++ b/drivers/iio/adc/ad7380.c
@@ -133,6 +133,9 @@ struct ad7380_state {
 	struct spi_device *spi;
 	struct regulator *vref;
 	struct regmap *regmap;
+	/* xfer and msg for buffer reads */
+	struct spi_transfer xfer;
+	struct spi_message msg;
 	/*
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache lines.
@@ -236,14 +239,9 @@ 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;
 
@@ -335,6 +333,28 @@ static const struct iio_info ad7380_info = {
 	.debugfs_reg_access = &ad7380_debugfs_reg_access,
 };
 
+static void ad7380_unoptimize_spi_msg(void *msg)
+{
+	spi_unoptimize_message(msg);
+}
+
+static int devm_ad7380_setup_spi_msg(struct device *dev, struct ad7380_state *st)
+{
+	int ret;
+
+	st->xfer.bits_per_word = st->chip_info->channels[0].scan_type.realbits;
+	st->xfer.len = 4;
+	st->xfer.rx_buf = st->scan_data.raw;
+
+	spi_message_init_with_transfers(&st->msg, &st->xfer, 1);
+
+	ret = spi_optimize_message(st->spi, &st->msg);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to optimize message\n");
+
+	return devm_add_action_or_reset(dev, ad7380_unoptimize_spi_msg, &st->msg);
+}
+
 static int ad7380_init(struct ad7380_state *st)
 {
 	int ret;
@@ -411,6 +431,10 @@ static int ad7380_probe(struct spi_device *spi)
 		return dev_err_probe(&spi->dev, PTR_ERR(st->regmap),
 				     "failed to allocate register map\n");
 
+	ret = devm_ad7380_setup_spi_msg(&spi->dev, st);
+	if (ret)
+		return ret;
+
 	indio_dev->channels = st->chip_info->channels;
 	indio_dev->num_channels = st->chip_info->num_channels;
 	indio_dev->name = st->chip_info->name;

-- 
2.43.2