linux-kernel - Re: [PATCH v6 7/7] iio: accel: adxl345: Add spi-3wire option

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Date: Sat, 30 Mar 2024 15:29:49 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Lothar Rubusch <l.rubusch@...il.com>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, eraretuya@...il.com
Subject: Re: [PATCH v6 7/7] iio: accel: adxl345: Add spi-3wire option

On Fri, 29 Mar 2024 00:40:30 +0000
Lothar Rubusch <l.rubusch@...il.com> wrote:

> Add a setup function implementation to the spi module to enable spi-3wire
> when specified in the device-tree.
> 
> Signed-off-by: Lothar Rubusch <l.rubusch@...il.com>
> ---
>  drivers/iio/accel/adxl345.h     |  1 +
>  drivers/iio/accel/adxl345_spi.c | 12 +++++++++++-
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/accel/adxl345.h b/drivers/iio/accel/adxl345.h
> index e859c01d4..3d5c8719d 100644
> --- a/drivers/iio/accel/adxl345.h
> +++ b/drivers/iio/accel/adxl345.h
> @@ -31,6 +31,7 @@
>  #define ADXL345_DATA_FORMAT_RANGE	GENMASK(1, 0)	/* Set the g range */
>  #define ADXL345_DATA_FORMAT_JUSTIFY	BIT(2)	/* Left-justified (MSB) mode */
>  #define ADXL345_DATA_FORMAT_FULL_RES	BIT(3)	/* Up to 13-bits resolution */
> +#define ADXL345_DATA_FORMAT_SPI_3WIRE	BIT(6)	/* 3-wire SPI mode */
>  #define ADXL345_DATA_FORMAT_SELF_TEST	BIT(7)	/* Enable a self test */
>  
>  #define ADXL345_DATA_FORMAT_2G		0
> diff --git a/drivers/iio/accel/adxl345_spi.c b/drivers/iio/accel/adxl345_spi.c
> index 1c0513bd3..f145d5c1d 100644
> --- a/drivers/iio/accel/adxl345_spi.c
> +++ b/drivers/iio/accel/adxl345_spi.c
> @@ -20,6 +20,16 @@ static const struct regmap_config adxl345_spi_regmap_config = {
>  	.read_flag_mask = BIT(7) | BIT(6),
>  };
>  
> +static int adxl345_spi_setup(struct device *dev, struct regmap *regmap)
> +{
> +	struct spi_device *spi = container_of(dev, struct spi_device, dev);
> +
> +	if (spi->mode & SPI_3WIRE)
> +		return regmap_write(regmap, ADXL345_REG_DATA_FORMAT,
> +				    ADXL345_DATA_FORMAT_SPI_3WIRE);
My only remaining comment on this patch set is to add equivalent of
	else
		return regmap_write(regmap, ADXL345_REG_DATA_FORMAT, 0);

If the hardware had some sort of software reset, that was used,
this wouldn't be needed as the status of those other bits would be known.
If we leave them alone in the non 3wire path we may in the future have
subtle issues because some other code left this in an odd state and
we clear those other bits only for 3wire mode.

Jonathan

> +	return 0;
> +}
> +
>  static int adxl345_spi_probe(struct spi_device *spi)
>  {
>  	struct regmap *regmap;
> @@ -33,7 +43,7 @@ static int adxl345_spi_probe(struct spi_device *spi)
>  	if (IS_ERR(regmap))
>  		return dev_err_probe(&spi->dev, PTR_ERR(regmap), "Error initializing regmap\n");
>  
> -	return adxl345_core_probe(&spi->dev, regmap, NULL);
> +	return adxl345_core_probe(&spi->dev, regmap, adxl345_spi_setup);
>  }
>  
>  static const struct adxl345_chip_info adxl345_spi_info = {