linux-kernel - Re: [PATCH] iio: filter: admv8818: Force initialization of SDO

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Message-ID: <20250125122610.4d084c13@jic23-huawei>
Date: Sat, 25 Jan 2025 12:26:10 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Sam Winchenbach <swinchenbach@...a.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
 "antoniu.miclaus@...log.com" <antoniu.miclaus@...log.com>,
 "lars@...afoo.de" <lars@...afoo.de>, "Michael.Hennerich@...log.com"
 <Michael.Hennerich@...log.com>
Subject: Re: [PATCH] iio: filter: admv8818: Force initialization of SDO

On Fri, 24 Jan 2025 18:27:46 +0000
Sam Winchenbach <swinchenbach@...a.org> wrote:

> From f851ce8225fc239fcbfc2e06adaa93336a9242ae Mon Sep 17 00:00:00 2001
> From: Sam Winchenbach <swinchenbach@...a.org>
> Date: Thu, 23 Jan 2025 15:24:09 -0500
> Subject: [PATCH] iio: filter: admv8818: Force initialization of SDO
Hi Sam, we shouldn't be seeing the email header in the patch.

I can tidy that up if you can't fix it though. 
> 
> 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.
> 
Sounds like a fix, so could you send an appropriate Fixes tag
in a v2 and/or a reply to this email.

> Signed-off-by: Sam Winchenbach <swinchenbach@...a.org>
> ---
>  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;