linux-kernel - Re: [PATCH v3 5/5] iio: dac: ltc2664: Add driver for LTC2664 and LTC2672

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Date: Mon, 03 Jun 2024 15:12:36 +0200
From: Nuno Sá <noname.nuno@...il.com>
To: Kim Seer Paller <kimseer.paller@...log.com>,
 linux-kernel@...r.kernel.org,  linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org
Cc: Jonathan Cameron <jic23@...nel.org>, David Lechner
 <dlechner@...libre.com>,  Lars-Peter Clausen <lars@...afoo.de>, Liam
 Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, Dimitri
 Fedrau <dima.fedrau@...il.com>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Rob Herring <robh@...nel.org>, Conor Dooley <conor+dt@...nel.org>,  Michael
 Hennerich <michael.hennerich@...log.com>, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v3 5/5] iio: dac: ltc2664: Add driver for LTC2664 and
 LTC2672

On Mon, 2024-06-03 at 09:22 +0800, Kim Seer Paller wrote:
> LTC2664 4 channel, 16 bit Voltage Output SoftSpan DAC
> LTC2672 5 channel, 16 bit Current Output Softspan DAC
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202405241141.kYcxrSem-lkp@intel.com/

The above could be dropped. This is still not merged code :)

> Co-developed-by: Michael Hennerich <michael.hennerich@...log.com>
> Signed-off-by: Michael Hennerich <michael.hennerich@...log.com>
> Signed-off-by: Kim Seer Paller <kimseer.paller@...log.com>
> ---

LGTM... just a couple of minor points/questions that you can maybe take on if a re-
spin is needed.

Reviewed-by: Nuno Sa <nuno.sa@...log.com>

...

> 
> +static int ltc2664_scale_get(const struct ltc2664_state *st, int c)
> +{
> +	const struct ltc2664_chan *chan = &st->channels[c];
> +	const int (*span_helper)[2] = st->chip_info->span_helper;
> +	int span, fs;
> +
> +	span = chan->span;
> +	if (span < 0)
> +		return span;
> +
> +	fs = span_helper[span][1] - span_helper[span][0];
> +
> +	return (fs / 2500) * st->vref;

no need for ()

...

> 
> +static int ltc2664_channel_config(struct ltc2664_state *st)
> +{
> +	const struct ltc2664_chip_info *chip_info = st->chip_info;
> +	struct device *dev = &st->spi->dev;
> +	u32 reg, tmp[2], mspan;
> +	int ret, span = 0;
> +
> +	mspan = LTC2664_MSPAN_SOFTSPAN;
> +	ret = device_property_read_u32(dev, "adi,manual-span-operation-config",
> +				       &mspan);
> +	if (!ret) {
> +		if (!chip_info->manual_span_support)
> +			return dev_err_probe(dev, -EINVAL,
> +			       "adi,manual-span-operation-config not
> supported\n");
> +
> +		if (mspan > ARRAY_SIZE(ltc2664_mspan_lut))
> +			return dev_err_probe(dev, -EINVAL,
> +			       "adi,manual-span-operation-config not in range\n");
> +	}
> +
> +	st->rfsadj = 20000;
> +	ret = device_property_read_u32(dev, "adi,rfsadj-ohms", &st->rfsadj);
> +	if (!ret) {
> +		if (!chip_info->rfsadj_support)
> +			return dev_err_probe(dev, -EINVAL,
> +					     "adi,rfsadj-ohms not supported\n");
> +
> +		if (st->rfsadj < 19000 || st->rfsadj > 41000)
> +			return dev_err_probe(dev, -EINVAL,
> +					     "adi,rfsadj-ohms not in range\n");
> +	}
> +
> +	device_for_each_child_node_scoped(dev, child) {
> +		struct ltc2664_chan *chan;
> +
> +		ret = fwnode_property_read_u32(child, "reg", &reg);
> +		if (ret)
> +			return dev_err_probe(dev, ret,
> +					     "Failed to get reg property\n");
> +
> +		if (reg >= chip_info->num_channels)
> +			return dev_err_probe(dev, -EINVAL,
> +					     "reg bigger than: %d\n",
> +					     chip_info->num_channels);
> +
> +		chan = &st->channels[reg];
> +
> +		if (fwnode_property_read_bool(child, "adi,toggle-mode")) {
> +			chan->toggle_chan = true;
> +			/* assume sw toggle ABI */

Do we have any other option :)? For the ltc2668 driver (where this code came from),
we do have another way (driven by clocks) to toggle between outputs and hence the
comment.

BTW, there's a fair amount of duplicated code between this and ltc2668. At some point
we may see if it makes sense to add some common module. Anyways, fine for now.

- Nuno Sá