linux-kernel - Re: [PATCH v6 6/6] iio: adc: ad7606: add gain calibration support

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Message-ID: <20250525150452.6638a917@jic23-huawei>
Date: Sun, 25 May 2025 15:04:52 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Angelo Dureghello <adureghello@...libre.com>
Cc: David Lechner <dlechner@...libre.com>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>, Lars-Peter Clausen
 <lars@...afoo.de>, Michael Hennerich <Michael.Hennerich@...log.com>, Rob
 Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor
 Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v6 6/6] iio: adc: ad7606: add gain calibration support

On Thu, 22 May 2025 15:27:07 +0200
Angelo Dureghello <adureghello@...libre.com> wrote:

> From: Angelo Dureghello <adureghello@...libre.com>
> 
> Add gain calibration support, using resistor values set on devicetree,
> values to be set accordingly with ADC external RFilter, as explained in
> the ad7606c-16 datasheet, rev0, page 37.
> 
> Usage example in the fdt yaml documentation.
> 
> Tested-by: David Lechner <dlechner@...libre.com>
> Reviewed-by: Nuno Sá <nuno.sa@...log.com>
> Signed-off-by: Angelo Dureghello <adureghello@...libre.com>

A few minor things inline.

> @@ -355,6 +363,46 @@ static int ad7606_get_chan_config(struct iio_dev *indio_dev, int ch,
>  	return 0;
>  }
>  
> +static int ad7606_chan_calib_gain_setup(struct iio_dev *indio_dev)
> +{
> +	struct ad7606_state *st = iio_priv(indio_dev);
> +	unsigned int num_channels = st->chip_info->num_adc_channels;
> +	struct device *dev = st->dev;
> +	int ret;
> +
> +	/*
> +	 * This function is called once, and parses all the channel nodes,
> +	 * so continuing on next channel node on errors, informing of them.

This doesn't seem correct any more as we don't continue on error with exception
of ones around the optional rfilter-ohms value.

> +	 */
> +	device_for_each_child_node_scoped(dev, child) {
> +		u32 reg, r_gain;
> +
> +		ret = fwnode_property_read_u32(child, "reg", &reg);
> +		if (ret)
> +			return ret;
> +
> +		/* Chan reg is a 1-based index. */
> +		if (reg < 1 || reg > num_channels)
> +			return ret;
> +
> +		ret = fwnode_property_read_u32(child, "adi,rfilter-ohms",
> +					       &r_gain);
> +		if (ret)
> +			/* Keep the default register value. */
> +			continue;

Might be simpler to just write the default?

		r_gain = /*WHATEVER DEFAULT IS */
		fwnode_property_read_u32(child, "adi,rfilter-ohms", &r_gain);
		if (r_gain > A7606...


> +
> +		if (r_gain > AD7606_CALIB_GAIN_MAX)
> +			return -EINVAL;
> +
> +		ret = st->bops->reg_write(st, AD7606_CALIB_GAIN(reg - 1),
> +			DIV_ROUND_CLOSEST(r_gain, AD7606_CALIB_GAIN_STEP));
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}