Before trying the custom method of reading the sensor
as raw and then converting assuming 1000 scaling, just
use iio_read_channel_processed() which first tries to
see if the ADC can provide a processed value directly,
else reads raw and applies scaling inside of IIO
using the scale attributes of the ADC.
The code that hardcodes scaling to 1000 and assumes
a 12bit ADC is very dubious. I keep it around here
but I have a strong urge to just delete it.
This gives correct readings on the AB8500 thermistor
inputs used in the Ux500 HREFP520 platform for reading
battery and board temperature.
Cc: Peter Rosin <peda@xxxxxxxxxx>
Cc: Chris Lesiak <chris.lesiak@xxxxxxxxx>
Cc: Jonathan Cameron <jic23@xxxxxxxxx>
Cc: linux-iio@xxxxxxxxxxxxxxx
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
drivers/hwmon/ntc_thermistor.c | 29 ++++++++++++++++++++---------
1 file changed, 20 insertions(+), 9 deletions(-)
diff --git a/drivers/hwmon/ntc_thermistor.c b/drivers/hwmon/ntc_thermistor.c
index 3aad62a0e661..ac0d80faddf6 100644
--- a/drivers/hwmon/ntc_thermistor.c
+++ b/drivers/hwmon/ntc_thermistor.c
@@ -326,18 +326,29 @@ struct ntc_data {
static int ntc_adc_iio_read(struct ntc_thermistor_platform_data *pdata)
{
struct iio_channel *channel = pdata->chan;
- int raw, uv, ret;
+ int uv, ret;
- ret = iio_read_channel_raw(channel, &raw);
+ /* A processed voltage channel will return microvolts */
+ ret = iio_read_channel_processed(channel, &uv);
if (ret < 0) {
- pr_err("read channel() error: %d\n", ret);
- return ret;
- }
+ int raw;
- 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;
+ /*
+ * FIXME: This fallback to using a raw read and then right
+ * out assume the ADC is 12 bits and hard-coding scale
+ * to 1000 seems a bit dangerous. Should it simply be
+ * deleted?
+ */
+ ret = iio_read_channel_raw(channel, &raw);
+ if (ret < 0) {
+ pr_err("read channel() error: %d\n", ret);
+ return ret;
+ }
+ 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 uv;
--
2.29.2
