linux-kernel - Re: [PATCH v5 5/5] iio: adc: ad7606: add gain calibration support

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Message-ID: <aCsUo9LOMGbse3KO@smile.fi.intel.com>
Date: Mon, 19 May 2025 14:23:15 +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 v5 5/5] iio: adc: ad7606: add gain calibration support

On Mon, May 19, 2025 at 12:13:42PM +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) {
> +		u32 reg, r_gain;
> +
> +		ret = fwnode_property_read_u32(child, "reg", &reg);
> +		if (ret)
> +			continue;
> +
> +		/* Chan reg is a 1-based index. */
> +		if (reg < 1 || reg > num_channels) {
> +			dev_warn(dev, "wrong ch number (ignoring): %d\n", reg);
> +			continue;
> +		}

Like I said, we should leave the validation to the schema or do it correctly here.
Otherwise it's an inconsistency between DT schema validator and this check.
I.o.w. this check *allows* the b0rken DT to be handled and I think this is simply
wrong.

> +		ret = fwnode_property_read_u32(child, "adi,rfilter-ohms",
> +					       &r_gain);
> +		if (ret)
> +			/* Keep the default register value. */
> +			continue;
> +
> +		if (r_gain > AD7606_CALIB_GAIN_MAX) {
> +			dev_warn(dev, "wrong gain calibration value");
> +			continue;
> +		}

Same here.

> +		ret = st->bops->reg_write(st, AD7606_CALIB_GAIN(reg - 1),
> +			DIV_ROUND_CLOSEST(r_gain, AD7606_CALIB_GAIN_STEP));
> +		if (ret) {
> +			dev_warn(dev, "error writing r_gain");
> +			continue;

Not sure about this, though.

> +		}
> +	}

-- 
With Best Regards,
Andy Shevchenko