iio: imu: st_lsm6dsx: fix decimation factor estimation

This change “iio: imu: st_lsm6dsx: fix decimation factor estimation” (commit 5685b14) in Linux kernel is authored by Lorenzo Bianconi <lorenzo [at] kernel.org> on Thu Nov 28 17:55:18 2019 +0200.

Description of "iio: imu: st_lsm6dsx: fix decimation factor estimation"

The change “iio: imu: st_lsm6dsx: fix decimation factor estimation” introduces changes as follows.

iio: imu: st_lsm6dsx: fix decimation factor estimation

Fix decimation factor and sip estimation for LSM6DSM series
(max value for decimation factor is 32).
If gyro and accel sensors are enabled at 12.5Hz and 416Hz
respectively, decimation factor lookup will fail, producing
unaligned data.
Remove unused decimator filed in st_lsm6dsx_sensor structure.

Fixes: f8710f0357bc ("iio: imu: st_lsm6dsx: express odr in mHZ")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Linux kernel releases containing commit 5685b14

The Linux kernel releases containing this commit are as follows.

Linux kernel code changes from "iio: imu: st_lsm6dsx: fix decimation factor estimation"

There are 27 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h       |  2 --
 .../iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c    | 25 +++++++++++++------
 2 files changed, 18 insertions(+), 9 deletions(-)
 
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
index c605b153be41..510c4bd4a785 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
@@ -320,7 +320,6 @@ enum st_lsm6dsx_fifo_mode {
  * @odr: Output data rate of the sensor [Hz].
  * @watermark: Sensor watermark level.
  * @sip: Number of samples in a given pattern.
- * @decimator: FIFO decimation factor.
  * @ts_ref: Sensor timestamp reference for hw one.
  * @ext_info: Sensor settings if it is connected to i2c controller
  */
@@ -334,7 +333,6 @@ struct st_lsm6dsx_sensor {
 
 	u16 watermark;
 	u8 sip;
-	u8 decimator;
 	s64 ts_ref;
 
 	struct {
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
index d416990ae309..a70b04f14187 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
@@ -78,14 +78,20 @@ struct st_lsm6dsx_decimator_entry st_lsm6dsx_decimator_table[] = {
 	{ 32, 0x7 },
 };
 
-static int st_lsm6dsx_get_decimator_val(u8 val)
+static int
+st_lsm6dsx_get_decimator_val(struct st_lsm6dsx_sensor *sensor, u32 max_odr)
 {
 	const int max_size = ARRAY_SIZE(st_lsm6dsx_decimator_table);
+	u32 decimator =  max_odr / sensor->odr;
 	int i;
 
-	for (i = 0; i < max_size; i++)
-		if (st_lsm6dsx_decimator_table[i].decimator == val)
+	if (decimator > 1)
+		decimator = round_down(decimator, 2);
+
+	for (i = 0; i < max_size; i++) {
+		if (st_lsm6dsx_decimator_table[i].decimator == decimator)
 			break;
+	}
 
 	return i == max_size ? 0 : st_lsm6dsx_decimator_table[i].val;
 }
@@ -111,6 +117,13 @@ static void st_lsm6dsx_get_max_min_odr(struct st_lsm6dsx_hw *hw,
 	}
 }
 
+static u8 st_lsm6dsx_get_sip(struct st_lsm6dsx_sensor *sensor, u32 min_odr)
+{
+	u8 sip = sensor->odr / min_odr;
+
+	return sip > 1 ? round_down(sip, 2) : sip;
+}
+
 static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
 {
 	const struct st_lsm6dsx_reg *ts_dec_reg;
@@ -131,12 +144,10 @@ static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
 		sensor = iio_priv(hw->iio_devs[i]);
 		/* update fifo decimators and sample in pattern */
 		if (hw->enable_mask & BIT(sensor->id)) {
-			sensor->sip = sensor->odr / min_odr;
-			sensor->decimator = max_odr / sensor->odr;
-			data = st_lsm6dsx_get_decimator_val(sensor->decimator);
+			sensor->sip = st_lsm6dsx_get_sip(sensor, min_odr);
+			data = st_lsm6dsx_get_decimator_val(sensor, max_odr);
 		} else {
 			sensor->sip = 0;
-			sensor->decimator = 0;
 			data = 0;
 		}
 		ts_sip = max_t(u16, ts_sip, sensor->sip);

The commit for this change in Linux stable tree is 5685b14 (patch).

Last modified: 2020/02/08