iio: accel: bmi088: Modified the scale calculate

The units after application of scale are 100*m/s^2,
The scale calculation is only for the device
with the range of 3, 6, 12, and 24g,
but some other chips have a range of 2, 4, 6, and 8g.

Modified the scales from formula to a list, the scales in the list are
calculated as 9.8/32768*pow(2,reg41+1)*1.5, refer to datasheet 5.3.4.
The new units after the application of scale are m/s^2.

Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: LI Qingwu <Qing-wu.Li@leica-geosystems.com.cn>
Link: https://lore.kernel.org/r/20220526133359.2261928-2-Qing-wu.Li@leica-geosystems.com.cn
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/bmi088-accel-core.c

@@ -6,6 +6,7 @@
  * Copyright (c) 2018-2021, Topic Embedded Products
  */
 
+#include <linux/bitfield.h>
 #include <linux/delay.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
@@ -73,6 +74,8 @@
 #define BMI088_ACCEL_FIFO_MODE_FIFO			0x40
 #define BMI088_ACCEL_FIFO_MODE_STREAM			0x80
 
+#define BMIO088_ACCEL_ACC_RANGE_MSK			GENMASK(1, 0)
+
 enum bmi088_accel_axis {
 	AXIS_X,
 	AXIS_Y,
@@ -119,6 +122,7 @@ struct bmi088_accel_chip_info {
 	u8 chip_id;
 	const struct iio_chan_spec *channels;
 	int num_channels;
+	const int scale_table[4][2];
 };
 
 struct bmi088_accel_data {
@@ -280,6 +284,7 @@ static int bmi088_accel_read_raw(struct iio_dev *indio_dev,
 	struct bmi088_accel_data *data = iio_priv(indio_dev);
 	struct device *dev = regmap_get_device(data->regmap);
 	int ret;
+	int reg;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
@@ -330,13 +335,14 @@ static int bmi088_accel_read_raw(struct iio_dev *indio_dev,
 				return ret;
 
 			ret = regmap_read(data->regmap,
-					  BMI088_ACCEL_REG_ACC_RANGE, val);
+					  BMI088_ACCEL_REG_ACC_RANGE, &reg);
 			if (ret)
 				goto out_read_raw_pm_put;
 
-			*val2 = 15 - (*val & 0x3);
-			*val = 3 * 980;
-			ret = IIO_VAL_FRACTIONAL_LOG2;
+			reg = FIELD_GET(BMIO088_ACCEL_ACC_RANGE_MSK, reg);
+			*val  = data->chip_info->scale_table[reg][0];
+			*val2 = data->chip_info->scale_table[reg][1];
+			ret = IIO_VAL_INT_PLUS_MICRO;
 
 			goto out_read_raw_pm_put;
 		default:
@@ -432,6 +438,7 @@ static const struct bmi088_accel_chip_info bmi088_accel_chip_info_tbl[] = {
 		.chip_id = 0x1E,
 		.channels = bmi088_accel_channels,
 		.num_channels = ARRAY_SIZE(bmi088_accel_channels),
+		.scale_table = {{0, 897}, {0, 1794}, {0, 3589}, {0, 7178}},
 	},
 };