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hwmon: (ntc_thermistor) Use library interpolation

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The kernel has a helper function for linear interpolation so
use it. It incidentally makes the code easier to read as well.

Tested on the ST-Ericsson HREFv60plus hardware reference design
with two thermistors forming a thermal zone.

Cc: Peter Rosin <peda@axentia.se>
Cc: Chris Lesiak <chris.lesiak@licor.com>
Cc: linux-iio@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20210704222014.12058-1-linus.walleij@linaro.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Linus Walleij 2021-07-05 00:20:14 +02:00 committed by Guenter Roeck
parent 02c9dce4df
commit bd56c1e960
1 changed files with 11 additions and 9 deletions
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20
drivers/hwmon/ntc_thermistor.c
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@ -13,6 +13,7 @@
#include <linux/err.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/fixp-arith.h>
#include <linux/platform_data/ntc_thermistor.h>
@ -549,15 +550,16 @@ static int get_temp_mc(struct ntc_data *data, unsigned int ohm)
int temp;
lookup_comp(data, ohm, &low, &high);
if (low == high) {
/* Unable to use linear approximation */
temp = data->comp[low].temp_c * 1000;
} else {
temp = data->comp[low].temp_c * 1000 +
((data->comp[high].temp_c - data->comp[low].temp_c) *
1000 * ((int)ohm - (int)data->comp[low].ohm)) /
((int)data->comp[high].ohm - (int)data->comp[low].ohm);
}
/*
* First multiplying the table temperatures with 1000 to get to
* millicentigrades (which is what we want) and then interpolating
* will give the best precision.
*/
temp = fixp_linear_interpolate(data->comp[low].ohm,
data->comp[low].temp_c * 1000,
data->comp[high].ohm,
data->comp[high].temp_c * 1000,
ohm);
return temp;
}