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

[Nuno Sá]

On Mon, 2024-02-19 at 16:33 -0600, David Lechner wrote:
> 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>
> ---
> 

Reviewed-by: Nuno Sa <nuno.sa@xxxxxxxxxx>

> 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;
>