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hwmon: (ntc_thermistor) fix iio raw to microvolts conversion 

The function ntc_adc_iio_read was assuming both a 12 bit ADC and that
pullup_uv is the same as the ADC reference voltage.  If either
assumption is false, then the result is incorrect.

Attempt to use iio_convert_raw_to_processed to convert the raw value to
microvolts.  It will fail for iio channels that don't support support
IIO_CHAN_INFO_SCALE; in that case fall back to the assumptions.

Signed-off-by: Chris Lesiak <chris.lesiak@licor.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Chris Lesiak 2015-06-01 11:27:37 -05:00 committed by Guenter Roeck
parent e892b75ff5
commit 0315253b19
1 changed files with 8 additions and 7 deletions
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15
drivers/hwmon/ntc_thermistor.c
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@ -228,20 +228,21 @@ struct ntc_data {
static int ntc_adc_iio_read(struct ntc_thermistor_platform_data *pdata)
{
struct iio_channel *channel = pdata->chan;
s64 result;
int val, ret;
int raw, uv, ret;
ret = iio_read_channel_raw(channel, &val);
ret = iio_read_channel_raw(channel, &raw);
if (ret < 0) {
pr_err("read channel() error: %d\n", ret);
return ret;
}
/* unit: mV */
result = pdata->pullup_uv * (s64) val;
result >>= 12;
ret = iio_convert_raw_to_processed(channel, raw, &uv, 1000);
if (ret < 0) {
/* Assume 12 bit ADC with vref at pullup_uv */
uv = (pdata->pullup_uv * (s64)raw) >> 12;
}
return (int)result;
return uv;
}
static const struct of_device_id ntc_match[] = {