linux-kernel - Re: [PATCH v4 5/5] iio: adc: ad7606: add gain calibration support

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Message-ID: <r2tlw3yhjjqwytyswv7onglo7rvedyyireofyiqkwxiosrbiyl@tlk6ijhbr3cp>
Date: Thu, 22 May 2025 14:47:41 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: Andy Shevchenko <andy@...nel.org>
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 v4 5/5] iio: adc: ad7606: add gain calibration support

Hi Andy,

On 19.05.2025 13:14, Andy Shevchenko wrote:
> On Mon, May 19, 2025 at 11:40:09AM +0200, Angelo Dureghello wrote:
> > On 08.05.2025 22:00, Andy Shevchenko wrote:
> > > On Thu, May 08, 2025 at 12:06:09PM +0200, Angelo Dureghello wrote:
> 
> ...
> 
> > > > +	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;
> > > > +		}
> > > 
> > > But this will allow to have a broken DT. This check basically diminishes the
> > > effort of the DT schema validation. If there are limits one still would be able
> > > to create a DT that passes the driver but doesn't pass the validation.
> > 
> > fixed all your points on other patches of this patch-set. Still your
> > emails are going to google spam, just could catch them on friday. 
> > Really not clear why.
> 
> DKIM which I still need to configure...
> 
> > About the above, i understand, but the check is actually the same as
> > in ad7606_get_chan_config(), a warning that fdt is not correct, 
> > i dont see a blocking issue here now, so not going to change it
> > in this next patchset.
> 
> I think the 'continue' above is simply wrong. We should not allow to have
> broken tables. And I think it's kinda blocking issue.
>

Actually the driver is informing of an incorrect channel node and passes
to the next channel, instead of a probe-fail. It is not introducing any 
non-functionality, just skipping that channel.

Not a big issue for me to fix it and issue a v6. 

If it's really wrong and needed, then i should fix this same issue that
is there in other previously accepted parts.
 
> > > > +		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;
> > > > +		}
> > > > +
> > > > +		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;
> > > > +		}
> > > > +	}
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 

Regards,
angelo