Re: [PATCH 10/12] iio: imu: inv_icm42600: add accurate timestamping
From: Jean-Baptiste Maneyrol
Date: Mon May 18 2020 - 11:51:57 EST
Hi Jonathan,
reading timestamp register is here mainly because we can do it, and this is the only way to have the full 20 bits resolution.
But it is not very useful indeed. I will delete it.
I am not using timestamp stored inside the FIFO, because it is only present when having both accel and gyro on. There is no timestamp data for a single sensor, which is really too bad. That would have been helpful.
I will add more documentation about it. It is not that tricky, but need more deep explanations.
New series V2 is in preparation. And again my apologizes for ruining the mail text formatting.
Thanks,
JB
From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Sent: Friday, May 8, 2020 16:42
To: Jean-Baptiste Maneyrol <JManeyrol@xxxxxxxxxxxxxx>
Cc: jic23@xxxxxxxxxx <jic23@xxxxxxxxxx>; robh+dt@xxxxxxxxxx <robh+dt@xxxxxxxxxx>; robh@xxxxxxxxxx <robh@xxxxxxxxxx>; mchehab+huawei@xxxxxxxxxx <mchehab+huawei@xxxxxxxxxx>; davem@xxxxxxxxxxxxx <davem@xxxxxxxxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx <gregkh@xxxxxxxxxxxxxxxxxxx>;
linux-iio@xxxxxxxxxxxxxxx <linux-iio@xxxxxxxxxxxxxxx>; devicetree@xxxxxxxxxxxxxxx <devicetree@xxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx <linux-kernel@xxxxxxxxxxxxxxx>
Subject: Re: [PATCH 10/12] iio: imu: inv_icm42600: add accurate timestamping
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On Thu, 7 May 2020 16:42:20 +0200
Jean-Baptiste Maneyrol <jmaneyrol@xxxxxxxxxxxxxx> wrote:
> Add a timestamp channel with processed value that returns full
> precision 20 bits timestamp.
>
> Add a timestamping mechanism for buffer that provides accurate
> event timestamps when using watermark. This mechanism estimates
> device internal clock by comparing FIFO interrupts delta time and
> corresponding device elapsed time computed by parsing FIFO data.
Yikes. That is complex. Hmm. I always get lost in the maths in these
timestamp patches so my review may be a little superficial.
However a bit more in the way of docs would be good here.
The sysfs read of timestamp is unusual and I'm not really sure what it is for.
The delays in a sysfs read of that value are likely to be enough that it's
that useful for anything.
Also, do we make use of the timestamps within the fifo records?
J
>
> Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@xxxxxxxxxxxxxx>
> ---
> drivers/iio/imu/inv_icm42600/Makefile | 1 +
> drivers/iio/imu/inv_icm42600/inv_icm42600.h | 10 +-
> .../iio/imu/inv_icm42600/inv_icm42600_accel.c | 32 ++-
> .../imu/inv_icm42600/inv_icm42600_buffer.c | 28 +-
> .../iio/imu/inv_icm42600/inv_icm42600_core.c | 6 +
> .../iio/imu/inv_icm42600/inv_icm42600_gyro.c | 32 ++-
> .../imu/inv_icm42600/inv_icm42600_timestamp.c | 246 ++++++++++++++++++
> .../imu/inv_icm42600/inv_icm42600_timestamp.h | 82 ++++++
> 8 files changed, 421 insertions(+), 16 deletions(-)
> create mode 100644 drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c
> create mode 100644 drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.h
>
> diff --git a/drivers/iio/imu/inv_icm42600/Makefile b/drivers/iio/imu/inv_icm42600/Makefile
> index d6732118010c..1197b545a682 100644
> --- a/drivers/iio/imu/inv_icm42600/Makefile
> +++ b/drivers/iio/imu/inv_icm42600/Makefile
> @@ -7,6 +7,7 @@ inv-icm42600-y += inv_icm42600_accel.o
> inv-icm42600-y += inv_icm42600_temp.o
> inv-icm42600-y += inv_icm42600_trigger.o
> inv-icm42600-y += inv_icm42600_buffer.o
> +inv-icm42600-y += inv_icm42600_timestamp.o
>
> obj-$(CONFIG_INV_ICM42600_I2C) += inv-icm42600-i2c.o
> inv-icm42600-i2c-y += inv_icm42600_i2c.o
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600.h b/drivers/iio/imu/inv_icm42600/inv_icm42600.h
> index 947ca4dd245b..e15eddafe009 100644
> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600.h
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600.h
> @@ -16,6 +16,7 @@
> #include <linux/iio/trigger.h>
>
> #include "inv_icm42600_buffer.h"
> +#include "inv_icm42600_timestamp.h"
>
> enum inv_icm42600_chip {
> INV_CHIP_ICM42600,
> @@ -127,6 +128,7 @@ struct inv_icm42600_suspended {
> * @indio_accel: accelerometer IIO device.
> * @trigger: device internal interrupt trigger
> * @fifo: FIFO management structure.
> + * @timestamp: timestamp management structure.
> */
> struct inv_icm42600_state {
> struct mutex lock;
> @@ -142,6 +144,10 @@ struct inv_icm42600_state {
> struct iio_dev *indio_accel;
> struct iio_trigger *trigger;
> struct inv_icm42600_fifo fifo;
> + struct {
> + struct inv_icm42600_timestamp gyro;
> + struct inv_icm42600_timestamp accel;
> + } timestamp;
> };
>
> /* Virtual register addresses: @bank on MSB (4 upper bits), @address on LSB */
> @@ -382,11 +388,11 @@ int inv_icm42600_core_probe(struct regmap *regmap, int chip, int irq,
>
> int inv_icm42600_gyro_init(struct inv_icm42600_state *st);
>
> -int inv_icm42600_gyro_parse_fifo(struct iio_dev *indio_dev, int64_t ts);
> +int inv_icm42600_gyro_parse_fifo(struct iio_dev *indio_dev);
>
> int inv_icm42600_accel_init(struct inv_icm42600_state *st);
>
> -int inv_icm42600_accel_parse_fifo(struct iio_dev *indio_dev, int64_t ts);
> +int inv_icm42600_accel_parse_fifo(struct iio_dev *indio_dev);
>
> int inv_icm42600_trigger_init(struct inv_icm42600_state *st, int irq,
> int irq_type);
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
> index 4206be54d057..ac140c824c03 100644
> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
> @@ -17,6 +17,7 @@
> #include "inv_icm42600.h"
> #include "inv_icm42600_temp.h"
> #include "inv_icm42600_buffer.h"
> +#include "inv_icm42600_timestamp.h"
>
> #define INV_ICM42600_ACCEL_CHAN(_modifier, _index, _ext_info) \
> { \
> @@ -66,7 +67,7 @@ static const struct iio_chan_spec inv_icm42600_accel_channels[] = {
> INV_ICM42600_ACCEL_CHAN(IIO_MOD_Z, INV_ICM42600_ACCEL_SCAN_Z,
> inv_icm42600_accel_ext_infos),
> INV_ICM42600_TEMP_CHAN(INV_ICM42600_ACCEL_SCAN_TEMP),
> - IIO_CHAN_SOFT_TIMESTAMP(INV_ICM42600_ACCEL_SCAN_TIMESTAMP),
> + INV_ICM42600_TIMESTAMP_CHAN(INV_ICM42600_ACCEL_SCAN_TIMESTAMP),
> };
>
> /* IIO buffer data */
> @@ -94,14 +95,20 @@ static irqreturn_t inv_icm42600_accel_handler(int irq, void *_data)
> struct iio_poll_func *pf = _data;
> struct iio_dev *indio_dev = pf->indio_dev;
> struct inv_icm42600_state *st = iio_device_get_drvdata(indio_dev);
> + struct inv_icm42600_timestamp *ts = &st->timestamp.accel;
> const size_t fifo_nb = st->fifo.nb.total;
> + const size_t accel_nb = st->fifo.nb.accel;
> + const uint32_t fifo_period = st->fifo.period;
> int ret;
>
> /* exit if no sample */
> if (fifo_nb == 0)
> goto out;
>
> - ret = inv_icm42600_accel_parse_fifo(indio_dev, pf->timestamp);
> + inv_icm42600_timestamp_interrupt(ts, fifo_period, fifo_nb, accel_nb,
> + pf->timestamp);
> +
> + ret = inv_icm42600_accel_parse_fifo(indio_dev);
> if (ret)
> dev_err(regmap_get_device(st->map), "accel fifo error %d\n",
> ret);
> @@ -143,6 +150,7 @@ static int inv_icm42600_accel_update_scan_mode(struct iio_dev *indio_dev,
> }
>
> /* update data FIFO write and FIFO watermark */
> + inv_icm42600_timestamp_apply_odr(&st->timestamp.accel, 0, 0, 0);
> ret = inv_icm42600_buffer_set_fifo_en(st, fifo_en | st->fifo.en);
> if (ret)
> goto out_unlock;
> @@ -347,6 +355,7 @@ static int inv_icm42600_accel_write_odr(struct inv_icm42600_state *st,
> mutex_lock(&st->lock);
> conf.odr = inv_icm42600_accel_odr_conv[idx / 2];
> ret = inv_icm42600_set_accel_conf(st, &conf, NULL);
> + inv_icm42600_timestamp_update_odr(&st->timestamp.accel, conf.odr);
> inv_icm42600_buffer_update_fifo_period(st);
> inv_icm42600_buffer_update_watermark(st);
> mutex_unlock(&st->lock);
> @@ -502,6 +511,9 @@ static int inv_icm42600_accel_read_raw(struct iio_dev *indio_dev,
> case IIO_TEMP:
> return inv_icm42600_temp_read_raw(indio_dev, chan, val, val2,
> mask);
> + case IIO_TIMESTAMP:
> + return inv_icm42600_timestamp_read_raw(indio_dev, chan, val,
> + val2, mask);
> default:
> return -EINVAL;
> }
> @@ -694,13 +706,18 @@ int inv_icm42600_accel_init(struct inv_icm42600_state *st)
> return devm_iio_device_register(dev, st->indio_accel);
> }
>
> -int inv_icm42600_accel_parse_fifo(struct iio_dev *indio_dev, int64_t ts)
> +int inv_icm42600_accel_parse_fifo(struct iio_dev *indio_dev)
> {
> struct inv_icm42600_state *st = iio_device_get_drvdata(indio_dev);
> + struct inv_icm42600_timestamp *ts = &st->timestamp.accel;
> + const size_t fifo_nb = st->fifo.nb.total;
> const size_t accel_nb = st->fifo.nb.accel;
> + const uint32_t fifo_period = st->fifo.period;
> ssize_t i, size;
> + unsigned int no;
> const void *accel, *gyro, *temp, *timestamp;
> unsigned int odr;
> + int64_t ts_val;
> struct inv_icm42600_accel_buffer buffer;
>
> /* exit if no accel sample */
> @@ -708,7 +725,7 @@ int inv_icm42600_accel_parse_fifo(struct iio_dev *indio_dev, int64_t ts)
> return 0;
>
> /* parse all fifo packets */
> - for (i = 0; i < st->fifo.count; i += size) {
> + for (i = 0, no = 0; i < st->fifo.count; i += size, ++no) {
> size = inv_icm42600_fifo_decode_packet(&st->fifo.data[i],
> &accel, &gyro, &temp, ×tamp, &odr);
> dev_dbg(regmap_get_device(st->map), "accel packet size = %zd\n",
> @@ -721,9 +738,14 @@ int inv_icm42600_accel_parse_fifo(struct iio_dev *indio_dev, int64_t ts)
> dev_dbg(regmap_get_device(st->map), "skip accel data\n");
> continue;
> }
> + /* update odr */
> + if (odr & INV_ICM42600_SENSOR_ACCEL)
> + inv_icm42600_timestamp_apply_odr(ts, fifo_period,
> + fifo_nb, no);
> memcpy(&buffer.accel, accel, sizeof(buffer.accel));
> memcpy(&buffer.temp, temp, sizeof(buffer.temp));
> - iio_push_to_buffers_with_timestamp(indio_dev, &buffer, ts);
> + ts_val = inv_icm42600_timestamp_get(ts);
> + iio_push_to_buffers_with_timestamp(indio_dev, &buffer, ts_val);
> }
>
> return 0;
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c
> index b428abdc92ee..bea4c9810da7 100644
> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c
> @@ -15,6 +15,7 @@
> #include <linux/iio/trigger_consumer.h>
>
> #include "inv_icm42600.h"
> +#include "inv_icm42600_timestamp.h"
> #include "inv_icm42600_buffer.h"
>
> void inv_icm42600_buffer_update_fifo_period(struct inv_icm42600_state *st)
> @@ -194,14 +195,17 @@ static int inv_icm42600_buffer_postdisable(struct iio_dev *indio_dev)
> unsigned int *watermark;
> struct inv_icm42600_sensor_conf conf = INV_ICM42600_SENSOR_CONF_INIT;
> unsigned int sleep = 0;
> + struct inv_icm42600_timestamp *ts;
> int ret;
>
> if (indio_dev == st->indio_gyro) {
> sensor = INV_ICM42600_SENSOR_GYRO;
> watermark = &st->fifo.watermark.gyro;
> + ts = &st->timestamp.gyro;
> } else if (indio_dev == st->indio_accel) {
> sensor = INV_ICM42600_SENSOR_ACCEL;
> watermark = &st->fifo.watermark.accel;
> + ts = &st->timestamp.accel;
> } else {
> return -EINVAL;
> }
> @@ -223,6 +227,8 @@ static int inv_icm42600_buffer_postdisable(struct iio_dev *indio_dev)
> else
> ret = inv_icm42600_set_accel_conf(st, &conf, &sleep);
>
> + inv_icm42600_timestamp_reset(ts);
> +
> out_unlock:
> mutex_unlock(&st->lock);
> if (sleep)
> @@ -316,11 +322,25 @@ int inv_icm42600_buffer_hwfifo_flush(struct inv_icm42600_state *st,
> if (st->fifo.nb.total == 0)
> return 0;
>
> - ret = inv_icm42600_gyro_parse_fifo(st->indio_gyro, ts_gyro);
> - if (ret)
> - return ret;
> + if (st->fifo.nb.gyro > 0) {
> + inv_icm42600_timestamp_interrupt(&st->timestamp.gyro,
> + st->fifo.period, st->fifo.nb.total,
> + st->fifo.nb.gyro, ts_gyro);
> + ret = inv_icm42600_gyro_parse_fifo(st->indio_gyro);
> + if (ret)
> + return ret;
> + }
>
> - return inv_icm42600_accel_parse_fifo(st->indio_accel, ts_accel);
> + if (st->fifo.nb.accel > 0) {
> + inv_icm42600_timestamp_interrupt(&st->timestamp.accel,
> + st->fifo.period, st->fifo.nb.total,
> + st->fifo.nb.accel, ts_accel);
> + ret = inv_icm42600_accel_parse_fifo(st->indio_accel);
> + if (ret)
> + return ret;
> + }
> +
> + return ret;
> }
>
> int inv_icm42600_buffer_init(struct inv_icm42600_state *st)
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_core.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_core.c
> index 689089065ff9..563c4348de01 100644
> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_core.c
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_core.c
> @@ -15,6 +15,7 @@
>
> #include "inv_icm42600.h"
> #include "inv_icm42600_buffer.h"
> +#include "inv_icm42600_timestamp.h"
>
> static const struct regmap_range_cfg inv_icm42600_regmap_ranges[] = {
> {
> @@ -516,6 +517,11 @@ int inv_icm42600_core_probe(struct regmap *regmap, int chip, int irq,
> if (ret)
> return ret;
>
> + /* initialize timestamping */
> + ret = inv_icm42600_timestamp_init(st);
> + if (ret)
> + return ret;
> +
> /* setup FIFO buffer */
> ret = inv_icm42600_buffer_init(st);
> if (ret)
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
> index dafb104abc77..1245588170bd 100644
> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
> @@ -17,6 +17,7 @@
> #include "inv_icm42600.h"
> #include "inv_icm42600_temp.h"
> #include "inv_icm42600_buffer.h"
> +#include "inv_icm42600_timestamp.h"
>
> #define INV_ICM42600_GYRO_CHAN(_modifier, _index, _ext_info) \
> { \
> @@ -66,7 +67,7 @@ static const struct iio_chan_spec inv_icm42600_gyro_channels[] = {
> INV_ICM42600_GYRO_CHAN(IIO_MOD_Z, INV_ICM42600_GYRO_SCAN_Z,
> inv_icm42600_gyro_ext_infos),
> INV_ICM42600_TEMP_CHAN(INV_ICM42600_GYRO_SCAN_TEMP),
> - IIO_CHAN_SOFT_TIMESTAMP(INV_ICM42600_GYRO_SCAN_TIMESTAMP),
Interrupt timestamp was pretty much garbage, so I'd just not register that in the
first place. Introduce the timestamp for the first time in this patch.
> + INV_ICM42600_TIMESTAMP_CHAN(INV_ICM42600_GYRO_SCAN_TIMESTAMP),
> };
>
> /* IIO buffer data */
> @@ -94,14 +95,20 @@ static irqreturn_t inv_icm42600_gyro_handler(int irq, void *_data)
> struct iio_poll_func *pf = _data;
> struct iio_dev *indio_dev = pf->indio_dev;
> struct inv_icm42600_state *st = iio_device_get_drvdata(indio_dev);
> + struct inv_icm42600_timestamp *ts = &st->timestamp.gyro;
> const size_t fifo_nb = st->fifo.nb.total;
> + const size_t gyro_nb = st->fifo.nb.gyro;
> + const uint32_t fifo_period = st->fifo.period;
> int ret;
>
> /* exit if no sample */
> if (fifo_nb == 0)
> goto out;
>
> - ret = inv_icm42600_gyro_parse_fifo(indio_dev, pf->timestamp);
> + inv_icm42600_timestamp_interrupt(ts, fifo_period, fifo_nb, gyro_nb,
> + pf->timestamp);
> +
> + ret = inv_icm42600_gyro_parse_fifo(indio_dev);
> if (ret)
> dev_err(regmap_get_device(st->map), "gyro fifo error %d\n",
> ret);
> @@ -143,6 +150,7 @@ static int inv_icm42600_gyro_update_scan_mode(struct iio_dev *indio_dev,
> }
>
> /* update data FIFO write and FIFO watermark */
> + inv_icm42600_timestamp_apply_odr(&st->timestamp.gyro, 0, 0, 0);
> ret = inv_icm42600_buffer_set_fifo_en(st, fifo_en | st->fifo.en);
> if (ret)
> goto out_unlock;
> @@ -359,6 +367,7 @@ static int inv_icm42600_gyro_write_odr(struct inv_icm42600_state *st,
> mutex_lock(&st->lock);
> conf.odr = inv_icm42600_gyro_odr_conv[idx / 2];
> ret = inv_icm42600_set_gyro_conf(st, &conf, NULL);
> + inv_icm42600_timestamp_update_odr(&st->timestamp.gyro, conf.odr);
> inv_icm42600_buffer_update_fifo_period(st);
> inv_icm42600_buffer_update_watermark(st);
> mutex_unlock(&st->lock);
> @@ -514,6 +523,9 @@ static int inv_icm42600_gyro_read_raw(struct iio_dev *indio_dev,
> case IIO_TEMP:
> return inv_icm42600_temp_read_raw(indio_dev, chan, val, val2,
> mask);
> + case IIO_TIMESTAMP:
> + return inv_icm42600_timestamp_read_raw(indio_dev, chan, val,
> + val2, mask);
> default:
> return -EINVAL;
> }
> @@ -706,13 +718,18 @@ int inv_icm42600_gyro_init(struct inv_icm42600_state *st)
> return devm_iio_device_register(dev, st->indio_gyro);
> }
>
> -int inv_icm42600_gyro_parse_fifo(struct iio_dev *indio_dev, int64_t ts)
> +int inv_icm42600_gyro_parse_fifo(struct iio_dev *indio_dev)
> {
> struct inv_icm42600_state *st = iio_device_get_drvdata(indio_dev);
> + struct inv_icm42600_timestamp *ts = &st->timestamp.gyro;
> + const size_t fifo_nb = st->fifo.nb.total;
> const size_t gyro_nb = st->fifo.nb.gyro;
> + const uint32_t fifo_period = st->fifo.period;
> ssize_t i, size;
> + unsigned int no;
> const void *accel, *gyro, *temp, *timestamp;
> unsigned int odr;
> + int64_t ts_val;
> struct inv_icm42600_gyro_buffer buffer;
>
> /* exit if no gyro sample */
> @@ -720,7 +737,7 @@ int inv_icm42600_gyro_parse_fifo(struct iio_dev *indio_dev, int64_t ts)
> return 0;
>
> /* parse all fifo packets */
> - for (i = 0; i < st->fifo.count; i += size) {
> + for (i = 0, no = 0; i < st->fifo.count; i += size, ++no) {
> size = inv_icm42600_fifo_decode_packet(&st->fifo.data[i],
> &accel, &gyro, &temp, ×tamp, &odr);
> dev_dbg(regmap_get_device(st->map), "gyro packet size = %zd\n",
> @@ -733,9 +750,14 @@ int inv_icm42600_gyro_parse_fifo(struct iio_dev *indio_dev, int64_t ts)
> dev_dbg(regmap_get_device(st->map), "skip gyro data\n");
> continue;
> }
> + /* update odr */
> + if (odr & INV_ICM42600_SENSOR_GYRO)
> + inv_icm42600_timestamp_apply_odr(ts, fifo_period,
> + fifo_nb, no);
> memcpy(&buffer.gyro, gyro, sizeof(buffer.gyro));
> memcpy(&buffer.temp, temp, sizeof(buffer.temp));
> - iio_push_to_buffers_with_timestamp(indio_dev, &buffer, ts);
> + ts_val = inv_icm42600_timestamp_get(ts);
> + iio_push_to_buffers_with_timestamp(indio_dev, &buffer, ts_val);
> }
>
> return 0;
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c
> new file mode 100644
> index 000000000000..79cf777e2e84
> --- /dev/null
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.c
> @@ -0,0 +1,246 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2020 Invensense, Inc.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/mutex.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/regmap.h>
> +#include <linux/math64.h>
> +#include <linux/iio/iio.h>
> +
> +#include "inv_icm42600.h"
> +#include "inv_icm42600_timestamp.h"
> +
> +/* internal chip period is 32kHz, 31250ns */
> +#define INV_ICM42600_TIMESTAMP_PERIOD 31250
> +/* allow a jitter of +/- 2% */
> +#define INV_ICM42600_TIMESTAMP_JITTER 2
> +/* compute min and max periods accepted */
> +#define INV_ICM42600_TIMESTAMP_MIN_PERIOD(_p) \
> + (((_p) * (100 - INV_ICM42600_TIMESTAMP_JITTER)) / 100)
> +#define INV_ICM42600_TIMESTAMP_MAX_PERIOD(_p) \
> + (((_p) * (100 + INV_ICM42600_TIMESTAMP_JITTER)) / 100)
> +
> +static void inv_update_acc(struct inv_icm42600_timestamp_acc *acc, uint32_t val)
> +{
> + uint64_t sum = 0;
> + size_t i;
> +
> + acc->values[acc->idx++] = val;
> + if (acc->idx >= ARRAY_SIZE(acc->values))
> + acc->idx = 0;
> +
> + for (i = 0; i < ARRAY_SIZE(acc->values); ++i) {
> + if (acc->values[i] == 0)
> + break;
> + sum += acc->values[i];
> + }
> +
> + acc->val = div_u64(sum, i);
> +}
> +
> +static int inv_icm42600_timestamp_read(struct inv_icm42600_state *st,
> + uint32_t *ts)
> +{
> + struct device *dev = regmap_get_device(st->map);
> + __le32 raw;
> + int ret;
> +
> + pm_runtime_get_sync(dev);
> + mutex_lock(&st->lock);
> +
> + ret = regmap_write(st->map, INV_ICM42600_REG_SIGNAL_PATH_RESET,
> + INV_ICM42600_SIGNAL_PATH_RESET_TMST_STROBE);
> + if (ret)
> + goto exit;
> +
> + /* Read timestamp value 3 registers little-endian */
> + raw = 0;
> + ret = regmap_bulk_read(st->map, INV_ICM42600_REG_TMSTVAL, &raw, 3);
> + if (ret)
> + goto exit;
> +
> + *ts = (uint32_t)le32_to_cpu(raw);
> +exit:
> + mutex_unlock(&st->lock);
> + pm_runtime_mark_last_busy(dev);
> + pm_runtime_put_autosuspend(dev);
> + return ret;
> +}
> +
> +int inv_icm42600_timestamp_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + struct inv_icm42600_state *st = iio_device_get_drvdata(indio_dev);
> + uint32_t ts;
> + int ret;
> +
> + if (chan->type != IIO_TIMESTAMP)
> + return -EINVAL;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_PROCESSED:
> + ret = iio_device_claim_direct_mode(indio_dev);
> + if (ret)
> + return ret;
> + ret = inv_icm42600_timestamp_read(st, &ts);
> + iio_device_release_direct_mode(indio_dev);
Unusual to expose it as a readable channel. Why would you want to do this?
> + if (ret)
> + return ret;
> + *val = ts * 1000;
> + return IIO_VAL_INT;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static void inv_icm42600_init_ts(struct inv_icm42600_timestamp *ts,
> + struct device *dev, uint32_t period)
> +{
> + /* initial odr for sensor is 1kHz */
> + const uint32_t default_period = 1000000;
> +
> + ts->dev = dev;
> + ts->mult = default_period / INV_ICM42600_TIMESTAMP_PERIOD;
> + ts->new_mult = period / INV_ICM42600_TIMESTAMP_PERIOD;
> + ts->period = default_period;
> +
> + /* use theoretical value for chip period */
> + inv_update_acc(&ts->chip_period, INV_ICM42600_TIMESTAMP_PERIOD);
> +}
> +
> +int inv_icm42600_timestamp_init(struct inv_icm42600_state *st)
> +{
> + unsigned int val;
> +
> + inv_icm42600_init_ts(&st->timestamp.gyro, regmap_get_device(st->map),
> + inv_icm42600_odr_to_period(st->conf.gyro.odr));
> + inv_icm42600_init_ts(&st->timestamp.accel, regmap_get_device(st->map),
> + inv_icm42600_odr_to_period(st->conf.accel.odr));
> +
> + /* enable timestamp register */
> + val = INV_ICM42600_TMST_CONFIG_TMST_TO_REGS_EN |
> + INV_ICM42600_TMST_CONFIG_TMST_EN;
> + return regmap_update_bits(st->map, INV_ICM42600_REG_TMST_CONFIG,
> + INV_ICM42600_TMST_CONFIG_MASK, val);
> +}
> +
> +void inv_icm42600_timestamp_update_odr(struct inv_icm42600_timestamp *ts,
> + int odr)
> +{
> + uint32_t period;
> +
> + period = inv_icm42600_odr_to_period(odr);
> + ts->new_mult = period / INV_ICM42600_TIMESTAMP_PERIOD;
> + dev_dbg(ts->dev, "ts new mult: %u\n", ts->new_mult);
> +}
> +
> +static bool inv_validate_period(uint32_t period, uint32_t mult)
> +{
> + const uint32_t chip_period = INV_ICM42600_TIMESTAMP_PERIOD;
> + uint32_t period_min, period_max;
> +
> + /* check that time interval between interrupts is acceptable */
> + period_min = INV_ICM42600_TIMESTAMP_MIN_PERIOD(chip_period) * mult;
> + period_max = INV_ICM42600_TIMESTAMP_MAX_PERIOD(chip_period) * mult;
> + if (period > period_min && period < period_max)
> + return true;
> + else
> + return false;
> +}
> +
> +static bool inv_compute_chip_period(struct inv_icm42600_timestamp *ts,
> + uint32_t mult, uint32_t period)
> +{
> + uint32_t new_chip_period;
> +
> + if (!inv_validate_period(period, mult))
> + return false;
> +
> + /* update chip internal period estimation */
> + new_chip_period = period / mult;
> + inv_update_acc(&ts->chip_period, new_chip_period);
> +
> + dev_dbg(ts->dev, "ts chip period: %u - val %u\n", new_chip_period,
> + ts->chip_period.val);
> +
> + return true;
> +}
> +
> +void inv_icm42600_timestamp_interrupt(struct inv_icm42600_timestamp *ts,
> + uint32_t fifo_period, size_t fifo_nb,
> + size_t sensor_nb, int64_t timestamp)
> +{
> + struct inv_icm42600_timestamp_interval *it;
> + int64_t delta, interval;
> + const uint32_t fifo_mult = fifo_period / INV_ICM42600_TIMESTAMP_PERIOD;
> + uint32_t period = ts->period;
> + int32_t m;
> + bool valid = false;
> +
> + if (fifo_nb == 0)
> + return;
> +
> + /* update interrupt timestamp and compute chip and sensor periods */
> + it = &ts->it;
> + it->lo = it->up;
> + it->up = timestamp;
> + delta = it->up - it->lo;
> + dev_dbg(ts->dev, "ts it: %lld - %lld - %lld\n", it->lo, it->up, delta);
> + if (it->lo != 0) {
> + period = div_s64(delta, fifo_nb);
> + valid = inv_compute_chip_period(ts, fifo_mult, period);
> + if (valid)
> + ts->period = ts->mult * ts->chip_period.val;
> + }
> +
> + /* no previous data, compute theoritical value from interrupt */
> + if (ts->timestamp == 0) {
> + interval = (int64_t)ts->period * (int64_t)sensor_nb;
> + ts->timestamp = it->up - interval;
> + dev_dbg(ts->dev, "ts start: %lld\n", ts->timestamp);
> + return;
> + }
> +
> + /* if interrupt interval is valid, sync with interrupt timestamp */
> + if (valid) {
> + /* compute real fifo_period */
> + fifo_period = fifo_mult * ts->chip_period.val;
> + delta = it->lo - ts->timestamp;
> + while (delta >= (fifo_period * 3 / 2))
> + delta -= fifo_period;
> + /* compute maximal adjustment value */
> + m = INV_ICM42600_TIMESTAMP_MAX_PERIOD(ts->period) - ts->period;
> + if (delta > m)
> + delta = m;
> + else if (delta < -m)
> + delta = -m;
> + dev_dbg(ts->dev, "ts adj: %lld\n", delta);
> + ts->timestamp += delta;
> + }
> +}
> +
> +void inv_icm42600_timestamp_apply_odr(struct inv_icm42600_timestamp *ts,
> + uint32_t fifo_period, size_t fifo_nb,
> + unsigned int fifo_no)
> +{
> + int64_t interval;
> + uint32_t fifo_mult;
> +
> + ts->mult = ts->new_mult;
> + ts->period = ts->mult * ts->chip_period.val;
> + dev_dbg(ts->dev, "ts mult: %u\n", ts->mult);
> +
> + if (ts->timestamp != 0) {
> + /* compute real fifo period */
> + fifo_mult = fifo_period / INV_ICM42600_TIMESTAMP_PERIOD;
> + fifo_period = fifo_mult * ts->chip_period.val;
> + /* compute timestamp from current interrupt after ODR change */
> + interval = (int64_t)(fifo_nb - fifo_no) * (int64_t)fifo_period;
> + ts->timestamp = ts->it.up - interval;
> + dev_dbg(ts->dev, "ts new: %lld\n", ts->timestamp);
> + }
> +}
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.h b/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.h
> new file mode 100644
> index 000000000000..c865e1a9a7c8
> --- /dev/null
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_timestamp.h
> @@ -0,0 +1,82 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2020 Invensense, Inc.
> + */
> +
> +#ifndef INV_ICM42600_TIMESTAMP_H_
> +#define INV_ICM42600_TIMESTAMP_H_
> +
> +#include <linux/device.h>
> +#include <linux/iio/iio.h>
> +
> +struct inv_icm42600_state;
> +
> +struct inv_icm42600_timestamp_interval {
> + int64_t lo;
> + int64_t up;
> +};
> +
> +struct inv_icm42600_timestamp_acc {
> + uint32_t val;
> + size_t idx;
> + uint32_t values[32];
> +};
> +
> +struct inv_icm42600_timestamp {
> + struct device *dev;
> + struct inv_icm42600_timestamp_interval it;
> + int64_t timestamp;
> + uint32_t mult;
> + uint32_t new_mult;
> + uint32_t period;
> + struct inv_icm42600_timestamp_acc chip_period;
> +};
> +
> +#define INV_ICM42600_TIMESTAMP_CHAN(_index) \
> + { \
> + .type = IIO_TIMESTAMP, \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
> + .scan_index = _index, \
> + .scan_type = { \
> + .sign = 's', \
> + .realbits = 64, \
> + .storagebits = 64, \
> + }, \
> + }
> +
> +int inv_icm42600_timestamp_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask);
> +
> +int inv_icm42600_timestamp_init(struct inv_icm42600_state *st);
> +
> +void inv_icm42600_timestamp_update_odr(struct inv_icm42600_timestamp *ts,
> + int odr);
> +
> +void inv_icm42600_timestamp_interrupt(struct inv_icm42600_timestamp *ts,
> + uint32_t fifo_period, size_t fifo_nb,
> + size_t sensor_nb, int64_t timestamp);
> +
> +static inline int64_t
> +inv_icm42600_timestamp_get(struct inv_icm42600_timestamp *ts)
Perhaps timestamp_pop? Kind of indicates that you are destructively
retrieving a timetamp.
> +{
> + ts->timestamp += ts->period;
> + dev_dbg(ts->dev, "ts: %lld\n", ts->timestamp);
> +
> + return ts->timestamp;
> +}
> +
> +void inv_icm42600_timestamp_apply_odr(struct inv_icm42600_timestamp *ts,
> + uint32_t fifo_period, size_t fifo_nb,
> + unsigned int fifo_no);
> +
> +static inline void
> +inv_icm42600_timestamp_reset(struct inv_icm42600_timestamp *ts)
> +{
> + const struct inv_icm42600_timestamp_interval interval_init = {0LL, 0LL};
> +
> + ts->it = interval_init;
> + ts->timestamp = 0;
> +}
> +
> +#endif