linux-kernel - Re: [PATCH v3 5/5] iio: adc: ad7606: add gain calibration support

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Message-ID: <7f5f75c1-7750-4966-9362-2a46c5e5ba3e@baylibre.com>
Date: Thu, 8 May 2025 08:50:56 -0500
From: David Lechner <dlechner@...libre.com>
To: Angelo Dureghello <adureghello@...libre.com>,
 Nuno Sá <noname.nuno@...il.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 v3 5/5] iio: adc: ad7606: add gain calibration support

On 5/8/25 4:16 AM, Angelo Dureghello wrote:
> Hi all,
> On 07.05.2025 07:14, Nuno Sá wrote:
>> On Tue, 2025-05-06 at 23:03 +0200, 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) {
>>> +		u32 reg, r_gain;
>>> +
> 
> working on further features, i noticed this function is called
> for each channel, that is not correct, so need to fix this,
> will send a v4.

Why is this not correct? Each input could have an amplifier with different
series resistor value so this seems correct to me.

> 
> Regards,
> angelo
> 
>>> +		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, "wrong ch number (ignoring): %d\n", reg);
>>> +			continue;
>>> +		}
>>> +
>>
>> Sorry Angelo, just realized this now. Any reason for not treating the above as a real
>> invalid argument? It's minor and not a big deal but odd enough...
>>
>> - Nuno Sá
>>
>>> +		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_MAX)
>>> +			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),
>>> +			DIV_ROUND_CLOSEST(r_gain, AD7606_CALIB_GAIN_STEP));
>>> +		if (ret)
>>> +			return ret;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +