linux-kernel - Re: [PATCH v3 16/27] staging: iio: resolver: ad2s1210: read excitation frequency from control register

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Date:   Sat, 30 Sep 2023 16:08:11 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     David Lechner <dlechner@...libre.com>
Cc:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-staging@...ts.linux.dev,
        David Lechner <david@...hnology.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Nuno Sá <nuno.sa@...log.com>,
        Axel Haslam <ahaslam@...libre.com>,
        Philip Molloy <pmolloy@...libre.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 16/27] staging: iio: resolver: ad2s1210: read
 excitation frequency from control register

On Fri, 29 Sep 2023 12:23:21 -0500
David Lechner <dlechner@...libre.com> wrote:

> From: David Lechner <david@...hnology.com>
> 
> From: David Lechner <dlechner@...libre.com>
> 
> This modifies the ad2s1210_show_fexcit() function to read the excitation
> frequency from the control register. This way we don't have to keep
> track of the value and don't risk returning a stale value.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
Applied.

A bit more fuzz with this one as context was different for the first hunk.

Jonathan

> ---
> 
> v3 changes: None
> 
>  drivers/staging/iio/resolver/ad2s1210.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
> index 28ab877e1bc0..b15d71b17266 100644
> --- a/drivers/staging/iio/resolver/ad2s1210.c
> +++ b/drivers/staging/iio/resolver/ad2s1210.c
> @@ -76,7 +76,6 @@ struct ad2s1210_state {
>  	struct regmap *regmap;
>  	/** The external oscillator frequency in Hz. */
>  	unsigned long clkin_hz;
> -	unsigned int fexcit;
>  	u8 resolution;
>  	/** For reading raw sample value via SPI. */
>  	__be16 sample __aligned(IIO_DMA_MINALIGN);
> @@ -206,8 +205,6 @@ static int ad2s1210_reinit_excitation_frequency(struct ad2s1210_state *st,
>  	if (ret < 0)
>  		return ret;
>  
> -	st->fexcit = fexcit;
> -
>  	/*
>  	 * Software reset reinitializes the excitation frequency output.
>  	 * It does not reset any of the configuration registers.
> @@ -232,8 +229,22 @@ static ssize_t ad2s1210_show_fexcit(struct device *dev,
>  				    char *buf)
>  {
>  	struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
> +	unsigned int value;
> +	u16 fexcit;
> +	int ret;
>  
> -	return sprintf(buf, "%u\n", st->fexcit);
> +	mutex_lock(&st->lock);
> +	ret = regmap_read(st->regmap, AD2S1210_REG_EXCIT_FREQ, &value);
> +	if (ret < 0)
> +		goto error_ret;
> +
> +	fexcit = value * st->clkin_hz / (1 << 15);
> +
> +	ret = sprintf(buf, "%u\n", fexcit);
> +
> +error_ret:
> +	mutex_unlock(&st->lock);
> +	return ret;
>  }
>  
>  static ssize_t ad2s1210_store_fexcit(struct device *dev,
>