linux-kernel - Re: [PATCH v2 5/5] iio: adc: ad7606: add gain calibration support

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Message-ID: <aBTKW538TX-jw977@smile.fi.intel.com>
Date: Fri, 2 May 2025 16:36:27 +0300
From: Andy Shevchenko <andy@...nel.org>
To: Angelo Dureghello <adureghello@...libre.com>
Cc: Jonathan Cameron <jic23@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	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 v2 5/5] iio: adc: ad7606: add gain calibration support

On Fri, May 02, 2025 at 03:27:02PM +0200, Angelo Dureghello 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.

...

> +	device_for_each_child_node_scoped(dev, child) {
> +		int reg, r_gain;

Both are defined in DT as unsigned. Are you able to use int as u32 in DT compiler?

> +		ret = fwnode_property_read_u32(child, "reg", &reg);
> +		if (ret)
> +			return ret;
> +
> +		/* channel number (here) is from 1 to num_channels */
> +		if (reg < 1 || reg > num_channels) {
> +			dev_warn(dev, "invalid ch number (ignoring): %d\n", reg);
> +			continue;
> +		}
> +
> +		ret = fwnode_property_read_u32(child, "adi,rfilter-ohms",
> +					       &r_gain);
> +		if (ret == -EINVAL)
> +			/* Keep the default register value. */
> +			continue;
> +		if (ret)
> +			return ret;

> +		if (r_gain < AD7606_CALIB_GAIN_MIN ||
> +		    r_gain > AD7606_CALIB_GAIN_MAX)

Seems like minimum check is not needed. See above why.

> +			return dev_err_probe(st->dev, -EINVAL,
> +					     "wrong gain calibration value.");
> +
> +		/* Chan reg is 1-based index. */
> +		ret = st->bops->reg_write(st, AD7606_CALIB_GAIN(reg - 1),
> +					  r_gain / AD7606_CALIB_GAIN_STEP);

Wonder if we need DIV_ROUND_CLOSEST() instead...

> +		if (ret)
> +			return ret;
> +	}

-- 
With Best Regards,
Andy Shevchenko