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

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Message-ID: <y6hss7bo25hiwzzplbbhmdodpmqbgpkarqvemn3tn3fig26tb2@753sxtygndaz>
Date: Thu, 1 May 2025 15:35:52 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: David Lechner <dlechner@...libre.com>
Cc: Jonathan Cameron <jic23@...nel.org>, 
	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 5/5] iio: adc: ad7606: add gain calibration support

On 29.04.2025 17:46, David Lechner wrote:
> On 4/29/25 8:06 AM, Angelo Dureghello wrote:
> > From: Angelo Dureghello <adureghello@...libre.com>
> > 
> 
> ...
> 
> > +static int ad7606_chan_calib_gain_setup(struct iio_dev *indio_dev,
> > +					struct iio_chan_spec *chan)
> > +{
> > +	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;
> > +
> > +	device_for_each_child_node_scoped(dev, child) {
> > +		int reg, r_gain;
> > +
> > +		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);
> 
> Instead of...
> 
> > +		if (ret)
> > +			return ret;
> 
> ... we need:
> 
> 		if (ret == -EINVAL)
> 			r_gain = 0;
> 		else if (ret)
> 			return ret;
> 
> Otherwise driver fails to probe if adi,rfilter-ohms is missing.
>

Correct, i changed this before sending and could not catch it.
But not totally sure of applying a 0.
We are here after chip reset. So conceptually, would not apply any default,
ince it is already set after reset. What about:

		if (ret == -EINVAL)
			contnue;
		else if (ret)
			return ret;
 
> > +
> > +		if (r_gain < AD7606_CALIB_GAIN_MIN ||
> > +		    r_gain > AD7606_CALIB_GAIN_MAX)
> > +			return -EINVAL;
> > +
> 
> Also, return dev_err_probe() on the returns above would have made debugging
> easier.
> 
ack

> > +		/* Chan reg is 1-based index. */
> > +		ret = st->bops->reg_write(st, AD7606_CALIB_GAIN(reg - 1),
> > +					  r_gain / AD7606_CALIB_GAIN_STEP);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	return 0;
> > +}
> > +