iio: accel: st_accel: fix LIS3LV02 reading and scaling

The LIS3LV02 has a special bit that need to be set to get the
read values left aligned. Before this patch we get gibberish
like this:

iio_generic_buffer -a -c10 -n lis3lv02dl_accel
(...)
0.000000 -0.010042 -0.642688 19155832931907
0.000000 -0.010042 -0.642688 19155858751073

Which is because we read a raw value for 1g as 64 which is
the nominal 1024 for 1g shifted 4 bits to the left by being
right-aligned rather than left aligned.

Since all other sensors are left aligned, add some code to
set the special DAS (data alignment setting) bit to 1 so that
the right value is now read like this:

iio_generic_buffer -a -c10 -n lis3lv02dl_accel
(...)
0.000000 -0.147095 -10.120135 24761614364956
-0.029419 -0.176514 -10.120135 24761631624540

The scaling was weird as well: we have a gain of 1000 for 1g
and 3000 for 6g. I don't even remember how I came up with the
old values but they are wrong.

Fixes: 3acddf74f807 ("iio: st-sensors: add support for lis3lv02d accelerometer")
Cc: Lorenzo Bianconi <lorenzo.bianconi@st.com>
Cc: Giuseppe Barba <giuseppe.barba@st.com>
Cc: Denis Ciocca <denis.ciocca@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/iio/common/st_sensors.h b/include/linux/iio/common/st_sensors.h
index 228bd44efa4c..497f2b3a5a62 100644
--- a/include/linux/iio/common/st_sensors.h
+++ b/include/linux/iio/common/st_sensors.h
@@ -116,6 +116,16 @@ struct st_sensor_bdu {
 };
 
 /**
+ * struct st_sensor_das - ST sensor device data alignment selection
+ * @addr: address of the register.
+ * @mask: mask to write the das flag for left alignment.
+ */
+struct st_sensor_das {
+	u8 addr;
+	u8 mask;
+};
+
+/**
  * struct st_sensor_data_ready_irq - ST sensor device data-ready interrupt
  * @addr: address of the register.
  * @mask_int1: mask to enable/disable IRQ on INT1 pin.
@@ -185,6 +195,7 @@ struct st_sensor_transfer_function {
  * @enable_axis: Enable one or more axis of the sensor.
  * @fs: Full scale register and full scale list available.
  * @bdu: Block data update register.
+ * @das: Data Alignment Selection register.
  * @drdy_irq: Data ready register of the sensor.
  * @multi_read_bit: Use or not particular bit for [I2C/SPI] multi-read.
  * @bootime: samples to discard when sensor passing from power-down to power-up.
@@ -200,6 +211,7 @@ struct st_sensor_settings {
 	struct st_sensor_axis enable_axis;
 	struct st_sensor_fullscale fs;
 	struct st_sensor_bdu bdu;
+	struct st_sensor_das das;
 	struct st_sensor_data_ready_irq drdy_irq;
 	bool multi_read_bit;
 	unsigned int bootime;