Re: [PATCH v3] iio: filter: admv8818: Force initialization of SDO

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 3 Feb 2025 13:34:34 +0000
Sam Winchenbach <swinchenbach@arka.org> wrote:

> When a weak pull-up is present on the SDO line, regmap_update_bits fails
> to write both the SOFTRESET and SDOACTIVE bits because it incorrectly
> reads them as already set.
> 
> Since the soft reset disables the SDO line, performing a
> read-modify-write operation on ADI_SPI_CONFIG_A to enable the SDO line
> doesn't make sense. This change directly writes to the register instead
> of using regmap_update_bits.
> 
> Fixes: f34fe888ad05 ("iio:filter:admv8818: add support for ADMV8818")
> Signed-off-by: Sam Winchenbach <swinchenbach@arka.org>
Applied and marked for stable.

Thanks,

Jonathan
> ---
>  drivers/iio/filter/admv8818.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iio/filter/admv8818.c b/drivers/iio/filter/admv8818.c
> index 195e58bc4..9cd1eee84 100644
> --- a/drivers/iio/filter/admv8818.c
> +++ b/drivers/iio/filter/admv8818.c
> @@ -577,21 +577,15 @@ static int admv8818_init(struct admv8818_state *st)
>  	struct spi_device *spi = st->spi;
>  	unsigned int chip_id;
>  
> -	ret = regmap_update_bits(st->regmap, ADMV8818_REG_SPI_CONFIG_A,
> -				 ADMV8818_SOFTRESET_N_MSK |
> -				 ADMV8818_SOFTRESET_MSK,
> -				 FIELD_PREP(ADMV8818_SOFTRESET_N_MSK, 1) |
> -				 FIELD_PREP(ADMV8818_SOFTRESET_MSK, 1));
> +	ret = regmap_write(st->regmap, ADMV8818_REG_SPI_CONFIG_A,
> +			   ADMV8818_SOFTRESET_N_MSK | ADMV8818_SOFTRESET_MSK);
>  	if (ret) {
>  		dev_err(&spi->dev, "ADMV8818 Soft Reset failed.\n");
>  		return ret;
>  	}
>  
> -	ret = regmap_update_bits(st->regmap, ADMV8818_REG_SPI_CONFIG_A,
> -				 ADMV8818_SDOACTIVE_N_MSK |
> -				 ADMV8818_SDOACTIVE_MSK,
> -				 FIELD_PREP(ADMV8818_SDOACTIVE_N_MSK, 1) |
> -				 FIELD_PREP(ADMV8818_SDOACTIVE_MSK, 1));
> +	ret = regmap_write(st->regmap, ADMV8818_REG_SPI_CONFIG_A,
> +			   ADMV8818_SDOACTIVE_N_MSK | ADMV8818_SDOACTIVE_MSK);
>  	if (ret) {
>  		dev_err(&spi->dev, "ADMV8818 SDO Enable failed.\n");
>  		return ret;