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

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Message-ID: <60986dd1-e03c-47f7-980c-879a5ecf7c44@baylibre.com>
Date: Thu, 1 May 2025 09:26:11 -0500
From: David Lechner <dlechner@...libre.com>
To: Angelo Dureghello <adureghello@...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 5/1/25 8:35 AM, Angelo Dureghello wrote:
> 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;

Sure. A comment could help here and the continue makes else not needed.



 		if (ret == -EINVAL)
			/* Keep the default register value. */
 			contnue;
 		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;
>>> +}
>>> +