Re: [PATCH] iio: imu: st_lsm6dsx: add odr calibration feature

Jonathan Cameron
2019-10-12T13:20:11Z

On Mon, 7 Oct 2019 16:07:27 +0200
Lorenzo Bianconi <lorenzo@kernel.org> wrote:

> > On LSM6DSO/LSM6DSR/LSM6DSOX/ASM330LHH and ISH330DHCX
> > devices it is possible to trim the hardware timestamp
> > resolution through the FREQ_FINE[7:0] bits of the
> > INTERNAL_FREQ_FINE register, which contains the difference
> > in percentage of the effective ODR (and timestamp rate)
> > with respect to the typical value.
> >
> > The formula for calculating the effective ODR reported
> > in the application notes has been linearized to the first
> > order to simplify the calculation (pls. see note on source
> > code).
> >
> > This change may be useful in the outcome of CTS
> > tests regarding the SingleSensorTests and the
> > SensorTest#testSensorTimeStamps for high ODRs
> >
> > Signed-off-by: Mario Tesi <mario.tesi@st.com>
>
> Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Hi.

The leading tabs on the commit message are a bit unusual,
but as far as I can tell the code is good.

Applied to the togreg branch of iio.git and pushed out
as testing for the autobuilders to play with it.

Thanks,

Jonathan

>
> > ---
> > drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h | 4 ++++
> > drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c | 5 ++---
> > drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c | 23 +++++++++++++++++++++++
> > 3 files changed, 29 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> > index 7485423..9a40587 100644
> > --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> > +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> > @@ -153,12 +153,14 @@ struct st_lsm6dsx_fifo_ops {
> > * @hr_timer: Hw timer resolution register info (addr + mask).
> > * @fifo_en: Hw timer FIFO enable register info (addr + mask).
> > * @decimator: Hw timer FIFO decimator register info (addr + mask).
> > + * @freq_fine: Difference in % of ODR with respect to the typical.
> > */
> > struct st_lsm6dsx_hw_ts_settings {
> > struct st_lsm6dsx_reg timer_en;
> > struct st_lsm6dsx_reg hr_timer;
> > struct st_lsm6dsx_reg fifo_en;
> > struct st_lsm6dsx_reg decimator;
> > + u8 freq_fine;
> > };
> >
> > /**
> > @@ -344,6 +346,7 @@ struct st_lsm6dsx_sensor {
> > * @fifo_mode: FIFO operating mode supported by the device.
> > * @suspend_mask: Suspended sensor bitmask.
> > * @enable_mask: Enabled sensor bitmask.
> > + * @ts_gain: Hw timestamp rate after internal calibration.
> > * @ts_sip: Total number of timestamp samples in a given pattern.
> > * @sip: Total number of samples (acc/gyro/ts) in a given pattern.
> > * @buff: Device read buffer.
> > @@ -365,6 +368,7 @@ struct st_lsm6dsx_hw {
> > enum st_lsm6dsx_fifo_mode fifo_mode;
> > u8 suspend_mask;
> > u8 enable_mask;
> > + s64 ts_gain;
> > u8 ts_sip;
> > u8 sip;
> >
> > diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> > index cabd4bf..d7cacb9 100644
> > --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> > +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> > @@ -50,7 +50,6 @@
> >
> > #define ST_LSM6DSX_MAX_FIFO_ODR_VAL 0x08
> >
> > -#define ST_LSM6DSX_TS_SENSITIVITY 25000UL /* 25us */
> > #define ST_LSM6DSX_TS_RESET_VAL 0xaa
> >
> > struct st_lsm6dsx_decimator_entry {
> > @@ -423,7 +422,7 @@ int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
> > */
> > if (!reset_ts && ts >= 0xff0000)
> > reset_ts = true;
> > - ts *= ST_LSM6DSX_TS_SENSITIVITY;
> > + ts *= hw->ts_gain;
> >
> > offset += ST_LSM6DSX_SAMPLE_SIZE;
> > }
> > @@ -566,7 +565,7 @@ int st_lsm6dsx_read_tagged_fifo(struct st_lsm6dsx_hw *hw)
> > */
> > if (!reset_ts && ts >= 0xffff0000)
> > reset_ts = true;
> > - ts *= ST_LSM6DSX_TS_SENSITIVITY;
> > + ts *= hw->ts_gain;
> > } else {
> > st_lsm6dsx_push_tagged_data(hw, tag, iio_buff,
> > ts);
> > diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> > index bacc908..2b54ce1 100644
> > --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> > +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> > @@ -63,6 +63,8 @@
> >
> > #define ST_LSM6DSX_REG_WHOAMI_ADDR 0x0f
> >
> > +#define ST_LSM6DSX_TS_SENSITIVITY 25000UL /* 25us */
> > +
> > static const struct iio_chan_spec st_lsm6dsx_acc_channels[] = {
> > ST_LSM6DSX_CHANNEL_ACC(IIO_ACCEL, 0x28, IIO_MOD_X, 0),
> > ST_LSM6DSX_CHANNEL_ACC(IIO_ACCEL, 0x2a, IIO_MOD_Y, 1),
> > @@ -832,6 +834,7 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
> > .addr = 0x0a,
> > .mask = GENMASK(7, 6),
> > },
> > + .freq_fine = 0x63,
> > },
> > .shub_settings = {
> > .page_mux = {
> > @@ -1020,6 +1023,7 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
> > .addr = 0x0a,
> > .mask = GENMASK(7, 6),
> > },
> > + .freq_fine = 0x63,
> > },
> > .event_settings = {
> > .enable_reg = {
> > @@ -1185,6 +1189,7 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
> > .addr = 0x0a,
> > .mask = GENMASK(7, 6),
> > },
> > + .freq_fine = 0x63,
> > },
> > .shub_settings = {
> > .page_mux = {
> > @@ -1874,6 +1879,24 @@ static int st_lsm6dsx_init_hw_timer(struct st_lsm6dsx_hw *hw)
> > if (err < 0)
> > return err;
> > }
> > +
> > + /* calibrate timestamp sensitivity */
> > + hw->ts_gain = ST_LSM6DSX_TS_SENSITIVITY;
> > + if (ts_settings->freq_fine) {
> > + err = regmap_read(hw->regmap, ts_settings->freq_fine, &val);
> > + if (err < 0)
> > + return err;
> > +
> > + /*
> > + * linearize the AN5192 formula:
> > + * 1 / (1 + x) ~= 1 - x (Taylor’s Series)
> > + * ttrim[s] = 1 / (40000 * (1 + 0.0015 * val))
> > + * ttrim[ns] ~= 25000 - 37.5 * val
> > + * ttrim[ns] ~= 25000 - (37500 * val) / 1000
> > + */
> > + hw->ts_gain -= ((s8)val * 37500) / 1000;
> > + }
> > +
> > return 0;
> > }
> >
> > --
> > 2.7.4
> >