diff options
| author | Linus Walleij <linus.walleij@linaro.org> | 2021-07-05 00:20:14 +0200 |
|---|---|---|
| committer | Guenter Roeck <linux@roeck-us.net> | 2021-08-17 14:54:25 -0700 |
| commit | bd56c1e9603a4c645fcafdef8df9b2b04125d406 (patch) | |
| tree | 712cf55092bd4acbd1cdf173b6b305c5757e40ec /drivers | |
| parent | 02c9dce4df8dd23e67dac1074be732c65c0e67d8 (diff) | |
hwmon: (ntc_thermistor) Use library interpolation
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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/hwmon/ntc_thermistor.c | 20 |
1 files changed, 11 insertions, 9 deletions
diff --git a/drivers/hwmon/ntc_thermistor.c b/drivers/hwmon/ntc_thermistor.c index 18fd6f12ca16..cf26c44f2b88 100644 --- a/drivers/hwmon/ntc_thermistor.c +++ b/drivers/hwmon/ntc_thermistor.c @@ -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; } |