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// 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");