linux-kernel - Re: [PATCH v10 11/12] iio: adc: ad7768-1: add filter type and oversampling ratio attributes

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Message-ID: <aEE3gsbbOuBdI1ky@smile.fi.intel.com>
Date: Thu, 5 Jun 2025 09:21:54 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Jonathan Santos <Jonathan.Santos@...log.com>
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	nuno.sa@...log.com, Michael.Hennerich@...log.com,
	marcelo.schmitt@...log.com, jic23@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, marcelo.schmitt1@...il.com,
	linus.walleij@...aro.org, brgl@...ev.pl, lgirdwood@...il.com,
	broonie@...nel.org, jonath4nns@...il.com, dlechner@...libre.com,
	Pop Paul <paul.pop@...log.com>
Subject: Re: [PATCH v10 11/12] iio: adc: ad7768-1: add filter type and
 oversampling ratio attributes

On Wed, Jun 04, 2025 at 04:37:36PM -0300, Jonathan Santos wrote:
> Separate filter type and decimation rate from the sampling frequency
> attribute. The new filter type attribute enables sinc3, sinc3+rej60
> and wideband filters, which were previously unavailable.
> 
> Previously, combining decimation and MCLK divider in the sampling
> frequency obscured performance trade-offs. Lower MCLK divider
> settings increase power usage, while lower decimation rates reduce
> precision by decreasing averaging. By creating an oversampling
> attribute, which controls the decimation, users gain finer control
> over performance.
> 
> The addition of those attributes allows a wider range of sampling
> frequencies and more access to the device features. Sampling frequency
> table is updated after every digital filter parameter change.
> 
> Changes in the sampling frequency are not allowed anymore while in
> buffered mode.

...

> +static const int ad7768_dec_rate_values[8] = {
> +	8, 16, 32, 64, 128, 256, 512, 1024,
> +};
> +
> +/* Decimation rate range for sinc3 filter */
> +static const int ad7768_sinc3_dec_rate_range[3] = {
> +	32, 32, 163840

Also leave trailing comma here.

> +};

...

> +static const char * const ad7768_filter_enum[] = {
> +	[AD7768_FILTER_SINC5] = "sinc5",
> +	[AD7768_FILTER_SINC3] = "sinc3",
> +	[AD7768_FILTER_WIDEBAND] = "wideband",
> +	[AD7768_FILTER_SINC3_REJ60] = "sinc3+rej60"

Ditto.

>  };

...

> +static int ad7768_set_mclk_div(struct ad7768_state *st, unsigned int mclk_div)
> +{
> +	unsigned int mclk_div_value;
> +
> +	mclk_div_value = AD7768_PWR_MCLK_DIV(mclk_div);
> +	/*
> +	 * Set power mode based on mclk_div value.
> +	 * ECO_MODE is only recommended for MCLK_DIV 16

'= 16.' ?

> +	 */
> +	mclk_div_value |= mclk_div > AD7768_MCLK_DIV_16 ?
> +			  AD7768_PWR_PWRMODE(AD7768_FAST_MODE) :
> +			  AD7768_PWR_PWRMODE(AD7768_ECO_MODE);
> +
> +	return regmap_update_bits(st->regmap, AD7768_REG_POWER_CLOCK,
> +				  AD7768_PWR_MCLK_DIV_MSK | AD7768_PWR_PWRMODE_MSK,
> +				  mclk_div_value);
>  }

-- 
With Best Regards,
Andy Shevchenko