On Tue, 22 May 2018 16:18:22 +0200
Jean-Baptiste Maneyrol <jmaneyrol@xxxxxxxxxxxxxx> wrote:
> Check validity of interrupt timestamps by computing time between
> 2 interrupts. If it matches the chip frequency modulo 4%, it is
> used as the data timestamp and also for estimating the chip
> frequency measured from the system. Otherwise timestamp is
> computed using the estimated chip frequency.
>
> Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@xxxxxxxxxxxxxx>
Applied,
Thanks,
Jonathan
> ---
> drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 7 ++
> drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h | 8 +++
> drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 81 +++++++++++++++++++++-
> 3 files changed, 95 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> index 2c3e666aa970..93c64f30b615 100644
> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> @@ -295,6 +295,13 @@ static int inv_mpu6050_init_config(struct iio_dev *indio_dev)
> memcpy(&st->chip_config, hw_info[st->chip_type].config,
> sizeof(struct inv_mpu6050_chip_config));
>
> + /*
> + * Internal chip period is 1ms (1kHz).
> + * Let's use at the beginning the theorical value before measuring
> + * with interrupt timestamps.
> + */
> + st->chip_period = NSEC_PER_MSEC;
> +
> return inv_mpu6050_set_power_itg(st, false);
>
> error_power_off:
> diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
> index 6bc80ac9d120..de8391693e17 100644
> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
> @@ -125,6 +125,9 @@ struct inv_mpu6050_hw {
> * @map regmap pointer.
> * @irq interrupt number.
> * @irq_mask the int_pin_cfg mask to configure interrupt type.
> + * @chip_period: chip internal period estimation (~1kHz).
> + * @it_timestamp: timestamp from previous interrupt.
> + * @data_timestamp: timestamp for next data sample.
> */
> struct inv_mpu6050_state {
> struct mutex lock;
> @@ -142,6 +145,9 @@ struct inv_mpu6050_state {
> int irq;
> u8 irq_mask;
> unsigned skip_samples;
> + s64 chip_period;
> + s64 it_timestamp;
> + s64 data_timestamp;
> };
>
> /*register and associated bit definition*/
> @@ -223,6 +229,8 @@ struct inv_mpu6050_state {
> #define INV_MPU6050_LATCH_INT_EN 0x20
> #define INV_MPU6050_BIT_BYPASS_EN 0x2
>
> +/* Allowed timestamp period jitter in percent */
> +#define INV_MPU6050_TS_PERIOD_JITTER 4
>
> /* init parameters */
> #define INV_MPU6050_INIT_FIFO_RATE 50
> diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> index 7a4aaed83044..6930af413397 100644
> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> @@ -23,12 +23,89 @@
> #include <asm/unaligned.h>
> #include "inv_mpu_iio.h"
>
> +/**
> + * inv_mpu6050_update_period() - Update chip internal period estimation
> + *
> + * @st: driver state
> + * @timestamp: the interrupt timestamp
> + * @nb: number of data set in the fifo
> + *
> + * This function uses interrupt timestamps to estimate the chip period and
> + * to choose the data timestamp to come.
> + */
> +static void inv_mpu6050_update_period(struct inv_mpu6050_state *st,
> + s64 timestamp, size_t nb)
> +{
> + /* Period boundaries for accepting timestamp */
> + const s64 period_min =
> + (NSEC_PER_MSEC * (100 - INV_MPU6050_TS_PERIOD_JITTER)) / 100;
> + const s64 period_max =
> + (NSEC_PER_MSEC * (100 + INV_MPU6050_TS_PERIOD_JITTER)) / 100;
> + const unsigned divider = INV_MPU6050_FREQ_DIVIDER(st);
> + s64 delta, interval;
> + bool use_it_timestamp = false;
> +
> + if (st->it_timestamp == 0) {
> + /* not initialized, forced to use it_timestamp */
> + use_it_timestamp = true;
> + } else if (nb == 1) {
> + /*
> + * Validate the use of it timestamp by checking if interrupt
> + * has been delayed.
> + * nb > 1 means interrupt was delayed for more than 1 sample,
> + * so it's obviously not good.
> + * Compute the chip period between 2 interrupts for validating.
> + */
> + delta = (timestamp - st->it_timestamp) / divider;
> + if (delta > period_min && delta < period_max) {
> + /* update chip period and use it timestamp */
> + st->chip_period = (st->chip_period + delta) / 2;
> + use_it_timestamp = true;
> + }
> + }
> +
> + if (use_it_timestamp) {
> + /*
> + * Manage case of multiple samples in the fifo (nb > 1):
> + * compute timestamp corresponding to the first sample using
> + * estimated chip period.
> + */
> + interval = (nb - 1) * st->chip_period * divider;
> + st->data_timestamp = timestamp - interval;
> + }
> +
> + /* save it timestamp */
> + st->it_timestamp = timestamp;
> +}
> +
> +/**
> + * inv_mpu6050_get_timestamp() - Return the current data timestamp
> + *
> + * @st: driver state
> + * @return: current data timestamp
> + *
> + * This function returns the current data timestamp and prepares for next one.
> + */
> +static s64 inv_mpu6050_get_timestamp(struct inv_mpu6050_state *st)
> +{
> + s64 ts;
> +
> + /* return current data timestamp and increment */
> + ts = st->data_timestamp;
> + st->data_timestamp += st->chip_period * INV_MPU6050_FREQ_DIVIDER(st);
> +
> + return ts;
> +}
> +
> int inv_reset_fifo(struct iio_dev *indio_dev)
> {
> int result;
> u8 d;
> struct inv_mpu6050_state *st = iio_priv(indio_dev);
>
> + /* reset it timestamp validation */
> + st->it_timestamp = 0;
> +
> /* disable interrupt */
> result = regmap_write(st->map, st->reg->int_enable, 0);
> if (result) {
> @@ -97,7 +174,7 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
> int result;
> u8 data[INV_MPU6050_OUTPUT_DATA_SIZE];
> u16 fifo_count;
> - s64 timestamp = pf->timestamp;
> + s64 timestamp;
> int int_status;
> size_t i, nb;
>
> @@ -140,6 +217,7 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
> fifo_count = get_unaligned_be16(&data[0]);
> /* compute and process all complete datum */
> nb = fifo_count / bytes_per_datum;
> + inv_mpu6050_update_period(st, pf->timestamp, nb);
> for (i = 0; i < nb; ++i) {
> result = regmap_bulk_read(st->map, st->reg->fifo_r_w,
> data, bytes_per_datum);
> @@ -150,6 +228,7 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
> st->skip_samples--;
> continue;
> }
> + timestamp = inv_mpu6050_get_timestamp(st);
> iio_push_to_buffers_with_timestamp(indio_dev, data, timestamp);
> }
>
--
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