[PATCH v3 0/3] iio: accel: add MSA311 accelerometer driver

[Dmitry Rokosov <DDRokosov@sberdevices.ru>]

MSA311 is a tri-axial, low-g accelerometer with I2C digital output for
sensitivity consumer applications. It has dynamical user selectable full
scales range of +-2g/+-4g/+-8g/+-16g and allows acceleration measurements
with output data rates from 1Hz to 1000Hz.

Datasheet can be found at following URL:
https://cdn-shop.adafruit.com/product-files/5309/MSA311-V1.1-ENG.pdf

This driver supports following MSA311 features:
    - IIO interface
    - Different power modes: NORMAL and SUSPEND (using pm_runtime)
    - ODR (Output Data Rate) selection
    - Scale and samp_freq selection
    - IIO triggered buffer, IIO reg access
    - NEW_DATA interrupt + trigger

Below features to be done:
    - Motion Events: ACTIVE, TAP, ORIENT, FREEFALL
    - Low Power mode

Also this patchset has new vendor prefix for MEMSensing Microsystems and
MSA311 dt-binding schema.

You can test msa311 driver using libiio and gnuplot following below
instructions:
  $ # Create hrtimer trigger object
  $ mkdir /sys/kernel/config/iio/triggers/hrtimer/iio_hrtimer_trigger
  $ # Read 4K samples using msa311-new-data trigger (irq) and
  $ # buffer with depth equals to 64 samples and rotate device a little bit
  $ iio_readdev -u "local:" -b 64 -s 4096 -t msa311-new-data -T 0 \
  $             msa311 > /tmp/msa311.dat
  $ # Or using hrtimer trigger instead of msa311-new-data trigger
  $ iio_readdev -u "local:" -b 64 -s 4096 -t iio_hrtimer_trigger -T 0 \
  $                msa311 > /data/local/tmp/msa311.dat
  $ cat <<EOF >> msa311_data.gnu
  set title "MSA311 Accel Data"

  set key below

  set xdata time
  set format x "%H:%M\n%.4S"
  set xlabel "timestamp"

  set autoscale y

  plot 'msa311.dat' binary endian=little \
                    format='%int16%int16%int16%uint16%uint64' using \
                    (\$5/1000000000):(int(\$1)/16) title "acc_x" \
                    with lines,\\
       'msa311.dat' binary endian=little \
                    format='%int16%int16%int16%uint16%uint64' using \
                    (\$5/1000000000):(int(\$2)/16) title "acc_y" \
                    with lines,\\
       'msa311.dat' binary endian=little \
                    format='%int16%int16%int16%uint16%uint64' using \
                    (\$5/1000000000):(int(\$3)/16) title "acc_z" with lines
  EOF
  $ gnuplot --persist msa311_data.gnu

Changes:
* v2->v3:
    - removed MSA311_TIMESTAMP_CHANNEL() macro, used IIO_CHAN_SOFT_TIMESTAMP
      directly
    - do not call dev_err_probe() inside functions, which is used not only
      from probe() path
    - simplified error handling a little bit
    - used iio_device_claim_direct_mode() and
      iio_device_release_direct_mode() to lock attributes when buffer mode
      is enabled
    - prohibited sampling frequency changing during buffer usage because
      otherwise sometimes MSA311 returns outliers when frequency values
      grow up in the read operation moment
    - allowed scale value changing when buffer mode is enabled
    - removed IRQF_TRIGGER_RISING irq flag from irg registration because
      it's provided from device tree directly
    - do not switch off autosuspend from powerdown() devm callback,
      because it's already done from pm_runtime_disable() during
      devm pm_runtime actions
    - provided more information why we need force suspend state for MSA311
      in the powerdown flow
    - reworked comments stuff: removed obvious extra comments, provided
      more details in the complex driver code places

* v1->v2:
    - memsensing vendor prefix was moved to right place by
      alphabetical order
    - LOW mode mention was deleted, because LOW mode isn't supported
      in the current driver version
    - reworked some enums with gaps to defines
    - reworked register names as Jonathan mentioned in the v1
    - do not use regmap_field API for entire registers
    - deleted all extra comments
    - supported info_mask_*_avail bitmaps instead of explicit IIO attrs
      definitions, implemented read_avail() callback for samp_freq and
      scale values
    - msa311 mutex is still used to protect msa311 power transitions,
      samp_freq/scale tune and axes data handling; described this lock
      more informative
    - ask new_data interruption status from appropriate register,
      do not hold atomic variable for that
    - optimized reads of axes data by I2C using regmap_bulk API
    - use dev_err_probe() instead of dev_err() for all probe() code paths
    - from now all I2C bus communication failures are interpreted as errors
    - described wait_from_next() semantic better
    - deleted all unneeded pm wrappers
    - interpreter all axes data as __le16 type and adjust them to right
      format (endianness + sign) for raw() flow only
    - redesigned msa311_fs_table[] to 2D matrix (it's more comfortable
      format for read_avail() callback)
    - align and initialize msa311 buffer before pushing properly
    - use pm_runtime resume and suspend from buffer preenable/postdisable,
      deleted them from trigger set_state
    - supported multiple trigger usage (tested with external hrtimer
      trigger and internal new_data trigger)
    - moved all irq related stuff to msa311_setup_interrupts() routine
    - implemented msa311_powerdown() devm release action
    - reworked initialization of pm_runtime msa311 flow, use
      autosuspend logic
    - purged driver remove() callback, because of devm release logic runs
      all deinit stuff fully
    - fixed dts bindings problems
    - changed irq type in the dt-binding description, because interrupt
      type for msa311 should have the same type as i2c irq, for example
      using the gpio_intc it's IRQ_TYPE_EDGE_RISING usually. Otherwise
      we may lose irq map on the second and further insmod attempts

Dmitry Rokosov (3):
  dt-bindings: vendor-prefixes: add MEMSensing Microsystems Co., Ltd.
  iio: add MEMSensing MSA311 3-axis accelerometer driver
  dt-bindings: iio: accel: add dt-binding schema for msa311 accel driver

 .../bindings/iio/accel/memsensing,msa311.yaml |   52 +
 .../devicetree/bindings/vendor-prefixes.yaml  |    2 +
 MAINTAINERS                                   |    7 +
 drivers/iio/accel/Kconfig                     |   13 +
 drivers/iio/accel/Makefile                    |    2 +
 drivers/iio/accel/msa311.c                    | 1312 +++++++++++++++++
 6 files changed, 1388 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/accel/memsensing,msa311.yaml
 create mode 100644 drivers/iio/accel/msa311.c

-- 
2.36.0