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iio: afe: rescale: add RTD temperature sensor support

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An RTD (Resistance Temperature Detector) is a kind of temperature
sensor used to get a linear voltage to temperature reading within a
give range (usually 0 to 100 degrees Celsius). Common types of RTDs
include PT100, PT500, and PT1000.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220213025739.2561834-8-liambeguin@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Liam Beguin 2022-02-12 21:57:36 -05:00 committed by Jonathan Cameron
parent 8e74a48d17
commit 278fe1d2d3
1 changed files with 48 additions and 0 deletions
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48
drivers/iio/afe/iio-rescale.c
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@ -394,10 +394,52 @@ static int rescale_voltage_divider_props(struct device *dev,
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;
}
enum rescale_variant {
CURRENT_SENSE_AMPLIFIER,
CURRENT_SENSE_SHUNT,
VOLTAGE_DIVIDER,
TEMP_SENSE_RTD,
};
static const struct rescale_cfg rescale_cfg[] = {
@ -413,6 +455,10 @@ static const struct rescale_cfg rescale_cfg[] = {
.type = IIO_VOLTAGE,
.props = rescale_voltage_divider_props,
},
[TEMP_SENSE_RTD] = {
.type = IIO_TEMP,
.props = rescale_temp_sense_rtd_props,
},
};
static const struct of_device_id rescale_match[] = {
@ -422,6 +468,8 @@ static const struct of_device_id rescale_match[] = {
.data = &rescale_cfg[CURRENT_SENSE_SHUNT], },
{ .compatible = "voltage-divider",
.data = &rescale_cfg[VOLTAGE_DIVIDER], },
{ .compatible = "temperature-sense-rtd",
.data = &rescale_cfg[TEMP_SENSE_RTD], },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, rescale_match);