This sensor can perform samples averaging in hardware, but currently the
driver leaves this setting alone (default is no averaging).
This patch binds this HW setting to the "oversampling_ratio" IIO attribute
and allows the user to set the averaging as desired (the HW supports
averaging of 2, 5, 8 or 16 samples; in-between values are rounded up).
Cc: Hartmut Knaack <knaack.h@xxxxxx>
Cc: Lars-Peter Clausen <lars@xxxxxxxxxx>
Cc: Peter Meerwald-Stadler <pmeerw@xxxxxxxxxx>
Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Cc: Patrick Havelange <patrick.havelange@xxxxxxxxxxxxx>
Cc: Paresh Chaudhary <paresh.chaudhary@xxxxxxxxxxxxxxxxxxx>
Cc: Matt Weber <matthew.weber@xxxxxxxxxxxxxxxxxxx>
Cc: Matt Ranostay <matt.ranostay@xxxxxxxxxxxx>
Cc: Chuhong Yuan <hslester96@xxxxxxxxx>
Cc: Daniel Gomez <dagmcr@xxxxxxxxx>
Cc: linux-iio@xxxxxxxxxxxxxxx
Signed-off-by: Andrea Merello <andrea.merello@xxxxxxxxx>
---
drivers/iio/temperature/max31856.c | 46 +++++++++++++++++++++++++++++-
1 file changed, 45 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/temperature/max31856.c b/drivers/iio/temperature/max31856.c
index d97ba9ee1598..9f0f4f65dccd 100644
--- a/drivers/iio/temperature/max31856.c
+++ b/drivers/iio/temperature/max31856.c
@@ -12,6 +12,7 @@
#include <linux/spi/spi.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
+#include <linux/util_macros.h>
#include <dt-bindings/iio/temperature/thermocouple.h>
/*
* The MSB of the register value determines whether the following byte will
@@ -24,6 +25,8 @@
#define MAX31856_CR0_OCFAULT BIT(4)
#define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4)
#define MAX31856_CR0_FILTER_50HZ BIT(0)
+#define MAX31856_AVERAGING_MASK GENMASK(6, 4)
+#define MAX31856_AVERAGING_SHIFT 4
#define MAX31856_TC_TYPE_MASK GENMASK(3, 0)
#define MAX31856_FAULT_OVUV BIT(1)
#define MAX31856_FAULT_OPEN BIT(0)
@@ -50,7 +53,10 @@ static const struct iio_chan_spec max31856_channels[] = {
{ /* Thermocouple Temperature */
.type = IIO_TEMP,
.info_mask_separate =
- BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+ BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) |
+ BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE),
+ .info_mask_shared_by_type =
+ BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
},
{ /* Cold Junction Temperature */
.type = IIO_TEMP,
@@ -58,6 +64,8 @@ static const struct iio_chan_spec max31856_channels[] = {
.modified = 1,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+ .info_mask_shared_by_type =
+ BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
},
};
@@ -65,6 +73,7 @@ struct max31856_data {
struct spi_device *spi;
u32 thermocouple_type;
bool filter_50hz;
+ int averaging;
};
static int max31856_read(struct max31856_data *data, u8 reg,
@@ -109,6 +118,10 @@ static int max31856_init(struct max31856_data *data)
reg_cr1_val &= ~MAX31856_TC_TYPE_MASK;
reg_cr1_val |= data->thermocouple_type;
+
+ reg_cr1_val &= ~MAX31856_AVERAGING_MASK;
+ reg_cr1_val |= data->averaging << MAX31856_AVERAGING_SHIFT;
+
ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val);
if (ret)
return ret;
@@ -217,6 +230,9 @@ static int max31856_read_raw(struct iio_dev *indio_dev,
return IIO_VAL_INT_PLUS_MICRO;
}
break;
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ *val = 1 << data->averaging;
+ return IIO_VAL_INT;
default:
ret = -EINVAL;
break;
@@ -225,6 +241,33 @@ static int max31856_read_raw(struct iio_dev *indio_dev,
return ret;
}
+static int max31856_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct max31856_data *data = iio_priv(indio_dev);
+ int msb;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ if (val > 16 || val < 1)
+ return -EINVAL;
+ msb = fls(val) - 1;
+ /* Round up to next 2pow if needed */
+ if (BIT(msb) < val)
+ msb++;
+
+ data->averaging = msb;
+ max31856_init(data);
+ break;
+
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
@@ -313,6 +356,7 @@ static const struct attribute_group max31856_group = {
static const struct iio_info max31856_info = {
.read_raw = max31856_read_raw,
+ .write_raw = max31856_write_raw,
.attrs = &max31856_group,
};
--
2.17.1
