1 files changed, 611 insertions, 0 deletions

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
new file mode 100644
index 0000000000..56e5913ab8
--- /dev/null
+++ b/drivers/iio/afe/iio-rescale.c
@@ -0,0 +1,611 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * IIO rescale driver
+ *
+ * Copyright (C) 2018 Axentia Technologies AB
+ * Copyright (C) 2022 Liam Beguin <liambeguin@gmail.com>
+ *
+ * Author: Peter Rosin <peda@axentia.se>
+ */
+
+#include <linux/err.h>
+#include <linux/gcd.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+#include <linux/iio/afe/rescale.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/iio.h>
+
+int rescale_process_scale(struct rescale *rescale, int scale_type,
+			  int *val, int *val2)
+{
+	s64 tmp;
+	int _val, _val2;
+	s32 rem, rem2;
+	u32 mult;
+	u32 neg;
+
+	switch (scale_type) {
+	case IIO_VAL_INT:
+		*val *= rescale->numerator;
+		if (rescale->denominator == 1)
+			return scale_type;
+		*val2 = rescale->denominator;
+		return IIO_VAL_FRACTIONAL;
+	case IIO_VAL_FRACTIONAL:
+		/*
+		 * When the product of both scales doesn't overflow, avoid
+		 * potential accuracy loss (for in kernel consumers) by
+		 * keeping a fractional representation.
+		 */
+		if (!check_mul_overflow(*val, rescale->numerator, &_val) &&
+		    !check_mul_overflow(*val2, rescale->denominator, &_val2)) {
+			*val = _val;
+			*val2 = _val2;
+			return IIO_VAL_FRACTIONAL;
+		}
+		fallthrough;
+	case IIO_VAL_FRACTIONAL_LOG2:
+		tmp = (s64)*val * 1000000000LL;
+		tmp = div_s64(tmp, rescale->denominator);
+		tmp *= rescale->numerator;
+
+		tmp = div_s64_rem(tmp, 1000000000LL, &rem);
+		*val = tmp;
+
+		if (!rem)
+			return scale_type;
+
+		if (scale_type == IIO_VAL_FRACTIONAL)
+			tmp = *val2;
+		else
+			tmp = ULL(1) << *val2;
+
+		rem2 = *val % (int)tmp;
+		*val = *val / (int)tmp;
+
+		*val2 = rem / (int)tmp;
+		if (rem2)
+			*val2 += div_s64((s64)rem2 * 1000000000LL, tmp);
+
+		return IIO_VAL_INT_PLUS_NANO;
+	case IIO_VAL_INT_PLUS_NANO:
+	case IIO_VAL_INT_PLUS_MICRO:
+		mult = scale_type == IIO_VAL_INT_PLUS_NANO ? 1000000000L : 1000000L;
+
+		/*
+		 * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if either *val
+		 * OR *val2 is negative the schan scale is negative, i.e.
+		 * *val = 1 and *val2 = -0.5 yields -1.5 not -0.5.
+		 */
+		neg = *val < 0 || *val2 < 0;
+
+		tmp = (s64)abs(*val) * abs(rescale->numerator);
+		*val = div_s64_rem(tmp, abs(rescale->denominator), &rem);
+
+		tmp = (s64)rem * mult + (s64)abs(*val2) * abs(rescale->numerator);
+		tmp = div_s64(tmp, abs(rescale->denominator));
+
+		*val += div_s64_rem(tmp, mult, val2);
+
+		/*
+		 * If only one of the rescaler elements or the schan scale is
+		 * negative, the combined scale is negative.
+		 */
+		if (neg ^ ((rescale->numerator < 0) ^ (rescale->denominator < 0))) {
+			if (*val)
+				*val = -*val;
+			else
+				*val2 = -*val2;
+		}
+
+		return scale_type;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+EXPORT_SYMBOL_NS_GPL(rescale_process_scale, IIO_RESCALE);
+
+int rescale_process_offset(struct rescale *rescale, int scale_type,
+			   int scale, int scale2, int schan_off,
+			   int *val, int *val2)
+{
+	s64 tmp, tmp2;
+
+	switch (scale_type) {
+	case IIO_VAL_FRACTIONAL:
+		tmp = (s64)rescale->offset * scale2;
+		*val = div_s64(tmp, scale) + schan_off;
+		return IIO_VAL_INT;
+	case IIO_VAL_INT:
+		*val = div_s64(rescale->offset, scale) + schan_off;
+		return IIO_VAL_INT;
+	case IIO_VAL_FRACTIONAL_LOG2:
+		tmp = (s64)rescale->offset * (1 << scale2);
+		*val = div_s64(tmp, scale) + schan_off;
+		return IIO_VAL_INT;
+	case IIO_VAL_INT_PLUS_NANO:
+		tmp = (s64)rescale->offset * 1000000000LL;
+		tmp2 = ((s64)scale * 1000000000LL) + scale2;
+		*val = div64_s64(tmp, tmp2) + schan_off;
+		return IIO_VAL_INT;
+	case IIO_VAL_INT_PLUS_MICRO:
+		tmp = (s64)rescale->offset * 1000000LL;
+		tmp2 = ((s64)scale * 1000000LL) + scale2;
+		*val = div64_s64(tmp, tmp2) + schan_off;
+		return IIO_VAL_INT;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+EXPORT_SYMBOL_NS_GPL(rescale_process_offset, IIO_RESCALE);
+
+static int rescale_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct rescale *rescale = iio_priv(indio_dev);
+	int scale, scale2;
+	int schan_off = 0;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (rescale->chan_processed)
+			/*
+			 * When only processed channels are supported, we
+			 * read the processed data and scale it by 1/1
+			 * augmented with whatever the rescaler has calculated.
+			 */
+			return iio_read_channel_processed(rescale->source, val);
+		else
+			return iio_read_channel_raw(rescale->source, val);
+
+	case IIO_CHAN_INFO_SCALE:
+		if (rescale->chan_processed) {
+			/*
+			 * Processed channels are scaled 1-to-1
+			 */
+			*val = 1;
+			*val2 = 1;
+			ret = IIO_VAL_FRACTIONAL;
+		} else {
+			ret = iio_read_channel_scale(rescale->source, val, val2);
+		}
+		return rescale_process_scale(rescale, ret, val, val2);
+	case IIO_CHAN_INFO_OFFSET:
+		/*
+		 * Processed channels are scaled 1-to-1 and source offset is
+		 * already taken into account.
+		 *
+		 * In other cases, real world measurement are expressed as:
+		 *
+		 *	schan_scale * (raw + schan_offset)
+		 *
+		 * Given that the rescaler parameters are applied recursively:
+		 *
+		 *	rescaler_scale * (schan_scale * (raw + schan_offset) +
+		 *		rescaler_offset)
+		 *
+		 * Or,
+		 *
+		 *	(rescaler_scale * schan_scale) * (raw +
+		 *		(schan_offset +	rescaler_offset / schan_scale)
+		 *
+		 * Thus, reusing the original expression the parameters exposed
+		 * to userspace are:
+		 *
+		 *	scale = schan_scale * rescaler_scale
+		 *	offset = schan_offset + rescaler_offset / schan_scale
+		 */
+		if (rescale->chan_processed) {
+			*val = rescale->offset;
+			return IIO_VAL_INT;
+		}
+
+		if (iio_channel_has_info(rescale->source->channel,
+					 IIO_CHAN_INFO_OFFSET)) {
+			ret = iio_read_channel_offset(rescale->source,
+						      &schan_off, NULL);
+			if (ret != IIO_VAL_INT)
+				return ret < 0 ? ret : -EOPNOTSUPP;
+		}
+
+		if (iio_channel_has_info(rescale->source->channel,
+					 IIO_CHAN_INFO_SCALE)) {
+			ret = iio_read_channel_scale(rescale->source, &scale, &scale2);
+			return rescale_process_offset(rescale, ret, scale, scale2,
+						      schan_off, val, val2);
+		}
+
+		/*
+		 * If we get here we have no scale so scale 1:1 but apply
+		 * rescaler and offset, if any.
+		 */
+		return rescale_process_offset(rescale, IIO_VAL_FRACTIONAL, 1, 1,
+					      schan_off, val, val2);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int rescale_read_avail(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      const int **vals, int *type, int *length,
+			      long mask)
+{
+	struct rescale *rescale = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*type = IIO_VAL_INT;
+		return iio_read_avail_channel_raw(rescale->source,
+						  vals, length);
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info rescale_info = {
+	.read_raw = rescale_read_raw,
+	.read_avail = rescale_read_avail,
+};
+
+static ssize_t rescale_read_ext_info(struct iio_dev *indio_dev,
+				     uintptr_t private,
+				     struct iio_chan_spec const *chan,
+				     char *buf)
+{
+	struct rescale *rescale = iio_priv(indio_dev);
+
+	return iio_read_channel_ext_info(rescale->source,
+					 rescale->ext_info[private].name,
+					 buf);
+}
+
+static ssize_t rescale_write_ext_info(struct iio_dev *indio_dev,
+				      uintptr_t private,
+				      struct iio_chan_spec const *chan,
+				      const char *buf, size_t len)
+{
+	struct rescale *rescale = iio_priv(indio_dev);
+
+	return iio_write_channel_ext_info(rescale->source,
+					  rescale->ext_info[private].name,
+					  buf, len);
+}
+
+static int rescale_configure_channel(struct device *dev,
+				     struct rescale *rescale)
+{
+	struct iio_chan_spec *chan = &rescale->chan;
+	struct iio_chan_spec const *schan = rescale->source->channel;
+
+	chan->indexed = 1;
+	chan->output = schan->output;
+	chan->ext_info = rescale->ext_info;
+	chan->type = rescale->cfg->type;
+
+	if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) &&
+	    (iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE) ||
+	     iio_channel_has_info(schan, IIO_CHAN_INFO_OFFSET))) {
+		dev_info(dev, "using raw+scale/offset source channel\n");
+	} else if (iio_channel_has_info(schan, IIO_CHAN_INFO_PROCESSED)) {
+		dev_info(dev, "using processed channel\n");
+		rescale->chan_processed = true;
+	} else {
+		dev_err(dev, "source channel is not supported\n");
+		return -EINVAL;
+	}
+
+	chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+		BIT(IIO_CHAN_INFO_SCALE);
+
+	if (rescale->offset)
+		chan->info_mask_separate |= BIT(IIO_CHAN_INFO_OFFSET);
+
+	/*
+	 * Using .read_avail() is fringe to begin with and makes no sense
+	 * whatsoever for processed channels, so we make sure that this cannot
+	 * be called on a processed channel.
+	 */
+	if (iio_channel_has_available(schan, IIO_CHAN_INFO_RAW) &&
+	    !rescale->chan_processed)
+		chan->info_mask_separate_available |= BIT(IIO_CHAN_INFO_RAW);
+
+	return 0;
+}
+
+static int rescale_current_sense_amplifier_props(struct device *dev,
+						 struct rescale *rescale)
+{
+	u32 sense;
+	u32 gain_mult = 1;
+	u32 gain_div = 1;
+	u32 factor;
+	int ret;
+
+	ret = device_property_read_u32(dev, "sense-resistor-micro-ohms",
+				       &sense);
+	if (ret) {
+		dev_err(dev, "failed to read the sense resistance: %d\n", ret);
+		return ret;
+	}
+
+	device_property_read_u32(dev, "sense-gain-mult", &gain_mult);
+	device_property_read_u32(dev, "sense-gain-div", &gain_div);
+
+	/*
+	 * Calculate the scaling factor, 1 / (gain * sense), or
+	 * gain_div / (gain_mult * sense), while trying to keep the
+	 * numerator/denominator from overflowing.
+	 */
+	factor = gcd(sense, 1000000);
+	rescale->numerator = 1000000 / factor;
+	rescale->denominator = sense / factor;
+
+	factor = gcd(rescale->numerator, gain_mult);
+	rescale->numerator /= factor;
+	rescale->denominator *= gain_mult / factor;
+
+	factor = gcd(rescale->denominator, gain_div);
+	rescale->numerator *= gain_div / factor;
+	rescale->denominator /= factor;
+
+	return 0;
+}
+
+static int rescale_current_sense_shunt_props(struct device *dev,
+					     struct rescale *rescale)
+{
+	u32 shunt;
+	u32 factor;
+	int ret;
+
+	ret = device_property_read_u32(dev, "shunt-resistor-micro-ohms",
+				       &shunt);
+	if (ret) {
+		dev_err(dev, "failed to read the shunt resistance: %d\n", ret);
+		return ret;
+	}
+
+	factor = gcd(shunt, 1000000);
+	rescale->numerator = 1000000 / factor;
+	rescale->denominator = shunt / factor;
+
+	return 0;
+}
+
+static int rescale_voltage_divider_props(struct device *dev,
+					 struct rescale *rescale)
+{
+	int ret;
+	u32 factor;
+
+	ret = device_property_read_u32(dev, "output-ohms",
+				       &rescale->denominator);
+	if (ret) {
+		dev_err(dev, "failed to read output-ohms: %d\n", ret);
+		return ret;
+	}
+
+	ret = device_property_read_u32(dev, "full-ohms",
+				       &rescale->numerator);
+	if (ret) {
+		dev_err(dev, "failed to read full-ohms: %d\n", ret);
+		return ret;
+	}
+
+	factor = gcd(rescale->numerator, rescale->denominator);
+	rescale->numerator /= factor;
+	rescale->denominator /= factor;
+
+	return 0;
+}
+
+static int rescale_temp_sense_rtd_props(struct device *dev,
+					struct rescale *rescale)
+{
+	u32 factor;
+	u32 alpha;
+	u32 iexc;
+	u32 tmp;
+	int ret;
+	u32 r0;
+
+	ret = device_property_read_u32(dev, "excitation-current-microamp",
+				       &iexc);
+	if (ret) {
+		dev_err(dev, "failed to read excitation-current-microamp: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = device_property_read_u32(dev, "alpha-ppm-per-celsius", &alpha);
+	if (ret) {
+		dev_err(dev, "failed to read alpha-ppm-per-celsius: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = device_property_read_u32(dev, "r-naught-ohms", &r0);
+	if (ret) {
+		dev_err(dev, "failed to read r-naught-ohms: %d\n", ret);
+		return ret;
+	}
+
+	tmp = r0 * iexc * alpha / 1000000;
+	factor = gcd(tmp, 1000000);
+	rescale->numerator = 1000000 / factor;
+	rescale->denominator = tmp / factor;
+
+	rescale->offset = -1 * ((r0 * iexc) / 1000);
+
+	return 0;
+}
+
+static int rescale_temp_transducer_props(struct device *dev,
+					 struct rescale *rescale)
+{
+	s32 offset = 0;
+	s32 sense = 1;
+	s32 alpha;
+	int ret;
+
+	device_property_read_u32(dev, "sense-offset-millicelsius", &offset);
+	device_property_read_u32(dev, "sense-resistor-ohms", &sense);
+	ret = device_property_read_u32(dev, "alpha-ppm-per-celsius", &alpha);
+	if (ret) {
+		dev_err(dev, "failed to read alpha-ppm-per-celsius: %d\n", ret);
+		return ret;
+	}
+
+	rescale->numerator = 1000000;
+	rescale->denominator = alpha * sense;
+
+	rescale->offset = div_s64((s64)offset * rescale->denominator,
+				  rescale->numerator);
+
+	return 0;
+}
+
+enum rescale_variant {
+	CURRENT_SENSE_AMPLIFIER,
+	CURRENT_SENSE_SHUNT,
+	VOLTAGE_DIVIDER,
+	TEMP_SENSE_RTD,
+	TEMP_TRANSDUCER,
+};
+
+static const struct rescale_cfg rescale_cfg[] = {
+	[CURRENT_SENSE_AMPLIFIER] = {
+		.type = IIO_CURRENT,
+		.props = rescale_current_sense_amplifier_props,
+	},
+	[CURRENT_SENSE_SHUNT] = {
+		.type = IIO_CURRENT,
+		.props = rescale_current_sense_shunt_props,
+	},
+	[VOLTAGE_DIVIDER] = {
+		.type = IIO_VOLTAGE,
+		.props = rescale_voltage_divider_props,
+	},
+	[TEMP_SENSE_RTD] = {
+		.type = IIO_TEMP,
+		.props = rescale_temp_sense_rtd_props,
+	},
+	[TEMP_TRANSDUCER] = {
+		.type = IIO_TEMP,
+		.props = rescale_temp_transducer_props,
+	},
+};
+
+static const struct of_device_id rescale_match[] = {
+	{ .compatible = "current-sense-amplifier",
+	  .data = &rescale_cfg[CURRENT_SENSE_AMPLIFIER], },
+	{ .compatible = "current-sense-shunt",
+	  .data = &rescale_cfg[CURRENT_SENSE_SHUNT], },
+	{ .compatible = "voltage-divider",
+	  .data = &rescale_cfg[VOLTAGE_DIVIDER], },
+	{ .compatible = "temperature-sense-rtd",
+	  .data = &rescale_cfg[TEMP_SENSE_RTD], },
+	{ .compatible = "temperature-transducer",
+	  .data = &rescale_cfg[TEMP_TRANSDUCER], },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rescale_match);
+
+static int rescale_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct iio_dev *indio_dev;
+	struct iio_channel *source;
+	struct rescale *rescale;
+	int sizeof_ext_info;
+	int sizeof_priv;
+	int i;
+	int ret;
+
+	source = devm_iio_channel_get(dev, NULL);
+	if (IS_ERR(source))
+		return dev_err_probe(dev, PTR_ERR(source),
+				     "failed to get source channel\n");
+
+	sizeof_ext_info = iio_get_channel_ext_info_count(source);
+	if (sizeof_ext_info) {
+		sizeof_ext_info += 1; /* one extra entry for the sentinel */
+		sizeof_ext_info *= sizeof(*rescale->ext_info);
+	}
+
+	sizeof_priv = sizeof(*rescale) + sizeof_ext_info;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof_priv);
+	if (!indio_dev)
+		return -ENOMEM;
+
+	rescale = iio_priv(indio_dev);
+
+	rescale->cfg = device_get_match_data(dev);
+	rescale->numerator = 1;
+	rescale->denominator = 1;
+	rescale->offset = 0;
+
+	ret = rescale->cfg->props(dev, rescale);
+	if (ret)
+		return ret;
+
+	if (!rescale->numerator || !rescale->denominator) {
+		dev_err(dev, "invalid scaling factor.\n");
+		return -EINVAL;
+	}
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	rescale->source = source;
+
+	indio_dev->name = dev_name(dev);
+	indio_dev->info = &rescale_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = &rescale->chan;
+	indio_dev->num_channels = 1;
+	if (sizeof_ext_info) {
+		rescale->ext_info = devm_kmemdup(dev,
+						 source->channel->ext_info,
+						 sizeof_ext_info, GFP_KERNEL);
+		if (!rescale->ext_info)
+			return -ENOMEM;
+
+		for (i = 0; rescale->ext_info[i].name; ++i) {
+			struct iio_chan_spec_ext_info *ext_info =
+				&rescale->ext_info[i];
+
+			if (source->channel->ext_info[i].read)
+				ext_info->read = rescale_read_ext_info;
+			if (source->channel->ext_info[i].write)
+				ext_info->write = rescale_write_ext_info;
+			ext_info->private = i;
+		}
+	}
+
+	ret = rescale_configure_channel(dev, rescale);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static struct platform_driver rescale_driver = {
+	.probe = rescale_probe,
+	.driver = {
+		.name = "iio-rescale",
+		.of_match_table = rescale_match,
+	},
+};
+module_platform_driver(rescale_driver);
+
+MODULE_DESCRIPTION("IIO rescale driver");
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
+MODULE_LICENSE("GPL v2");