linux-kernel - Re: [PATCH v2 14/19] staging: iio: resolver: ad2s1210: refactor setting excitation frequency

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Message-ID: <20230924190839.4ecd918d@jic23-huawei>
Date:   Sun, 24 Sep 2023 19:08:39 +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, linux-kernel@...r.kernel.org,
        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>
Subject: Re: [PATCH v2 14/19] staging: iio: resolver: ad2s1210: refactor
 setting excitation frequency

On Thu, 21 Sep 2023 09:43:55 -0500
David Lechner <dlechner@...libre.com> wrote:

> This combines the ad2s1210_update_frequency_control_word() and
> ad2s1210_soft_reset() functions into a single function since they
> both have to be called together.
> 
> Also clean up a few things while touching this:
> - move AD2S1210_DEF_EXCIT macro with similar macros
> - remove unnecessary dev_err() calls
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>


Probably worth calling out that this reset doesn't touch config
registers (they normally do!) but instead resets the tracking logic.

Jonathan

> ---
>  drivers/staging/iio/resolver/ad2s1210.c | 63 ++++++++++++-------------
>  1 file changed, 31 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
> index fe413759deb9..f1ffee34ebbc 100644
> --- a/drivers/staging/iio/resolver/ad2s1210.c
> +++ b/drivers/staging/iio/resolver/ad2s1210.c
> @@ -53,12 +53,11 @@
>  #define AD2S1210_MIN_CLKIN	6144000
>  #define AD2S1210_MAX_CLKIN	10240000
>  #define AD2S1210_MIN_EXCIT	2000
> +#define AD2S1210_DEF_EXCIT	10000
>  #define AD2S1210_MAX_EXCIT	20000
>  #define AD2S1210_MIN_FCW	0x4
>  #define AD2S1210_MAX_FCW	0x50
>  
> -#define AD2S1210_DEF_EXCIT	10000
> -
>  enum ad2s1210_mode {
>  	MOD_POS = 0b00,
>  	MOD_VEL = 0b01,
> @@ -184,18 +183,29 @@ static int ad2s1210_regmap_reg_read(void *context, unsigned int reg,
>  	return 0;
>  }
>  
> -static inline
> -int ad2s1210_update_frequency_control_word(struct ad2s1210_state *st)
> +/*
> + * Sets the excitation frequency and performs software reset.
> + *
> + * Must be called with lock held.
> + */
> +static int ad2s1210_set_excitation_frequency(struct ad2s1210_state *st,
> +					     u16 fexcit)
>  {
> -	unsigned char fcw;
> +	int ret;
> +	u8 fcw;
>  
> -	fcw = (unsigned char)(st->fexcit * (1 << 15) / st->fclkin);
> -	if (fcw < AD2S1210_MIN_FCW || fcw > AD2S1210_MAX_FCW) {
> -		dev_err(&st->sdev->dev, "ad2s1210: FCW out of range\n");
> +	fcw = fexcit * (1 << 15) / st->fclkin;
> +	if (fcw < AD2S1210_MIN_FCW || fcw > AD2S1210_MAX_FCW)
>  		return -ERANGE;
> -	}
>  
> -	return regmap_write(st->regmap, AD2S1210_REG_EXCIT_FREQ, fcw);
> +	ret = regmap_write(st->regmap, AD2S1210_REG_EXCIT_FREQ, fcw);
> +	if (ret < 0)
> +		return ret;
> +
> +	st->fexcit = fexcit;
> +
> +	/* software reset reinitializes the excitation frequency output */
> +	return regmap_write(st->regmap, AD2S1210_REG_SOFT_RESET, 0);
>  }
>  
>  static int ad2s1210_set_resolution_gpios(struct ad2s1210_state *st,
> @@ -210,11 +220,6 @@ static int ad2s1210_set_resolution_gpios(struct ad2s1210_state *st,
>  				     bitmap);
>  }
>  
> -static inline int ad2s1210_soft_reset(struct ad2s1210_state *st)
> -{
> -	return regmap_write(st->regmap, AD2S1210_REG_SOFT_RESET, 0);
> -}
> -
>  static ssize_t ad2s1210_show_fexcit(struct device *dev,
>  				    struct device_attribute *attr,
>  				    char *buf)
> @@ -229,27 +234,24 @@ static ssize_t ad2s1210_store_fexcit(struct device *dev,
>  				     const char *buf, size_t len)
>  {
>  	struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
> -	unsigned int fexcit;
> +	u16 fexcit;
>  	int ret;
>  
> -	ret = kstrtouint(buf, 10, &fexcit);
> -	if (ret < 0)
> -		return ret;
> -	if (fexcit < AD2S1210_MIN_EXCIT || fexcit > AD2S1210_MAX_EXCIT) {
> -		dev_err(dev,
> -			"ad2s1210: excitation frequency out of range\n");
> +	ret = kstrtou16(buf, 10, &fexcit);
> +	if (ret < 0 || fexcit < AD2S1210_MIN_EXCIT || fexcit > AD2S1210_MAX_EXCIT)
>  		return -EINVAL;
> -	}
> +
>  	mutex_lock(&st->lock);
> -	st->fexcit = fexcit;
> -	ret = ad2s1210_update_frequency_control_word(st);
> +	ret = ad2s1210_set_excitation_frequency(st, fexcit);
>  	if (ret < 0)
>  		goto error_ret;
> -	ret = ad2s1210_soft_reset(st);
> +
> +	ret = len;
> +
>  error_ret:
>  	mutex_unlock(&st->lock);
>  
> -	return ret < 0 ? ret : len;
> +	return ret;
>  }
>  
>  static ssize_t ad2s1210_show_resolution(struct device *dev,
> @@ -624,10 +626,8 @@ static int ad2s1210_initial(struct ad2s1210_state *st)
>  	if (ret < 0)
>  		goto error_ret;
>  
> -	ret = ad2s1210_update_frequency_control_word(st);
> -	if (ret < 0)
> -		goto error_ret;
> -	ret = ad2s1210_soft_reset(st);
> +	ret = ad2s1210_set_excitation_frequency(st, AD2S1210_DEF_EXCIT);
> +
>  error_ret:
>  	mutex_unlock(&st->lock);
>  	return ret;
> @@ -773,7 +773,6 @@ static int ad2s1210_probe(struct spi_device *spi)
>  	mutex_init(&st->lock);
>  	st->sdev = spi;
>  	st->resolution = 12;
> -	st->fexcit = AD2S1210_DEF_EXCIT;
>  
>  	ret = ad2s1210_setup_clocks(st);
>  	if (ret < 0)