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Date:   Sun, 22 Dec 2019 16:04:01 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Dan Robertson <dan@dlrobertson.com>,
        linux-iio <linux-iio@vger.kernel.org>,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        devicetree <devicetree@vger.kernel.org>,
        Hartmut Knaack <knaack.h@gmx.de>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Joe Perches <joe@perches.com>,
        Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCH v8 2/3] iio: (bma400) add driver for the BMA400
Message-ID: <20191222160401.63816074@archlinux>
In-Reply-To: <CAHp75Veko7f1cjrOdBf1quN40wJJLCDXaYzyY_AVy7T5tjGWQA@mail.gmail.com>
References: <20191220160051.26321-1-dan@dlrobertson.com>
        <20191220160051.26321-3-dan@dlrobertson.com>
        <CAHp75Veko7f1cjrOdBf1quN40wJJLCDXaYzyY_AVy7T5tjGWQA@mail.gmail.com>
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On Fri, 20 Dec 2019 18:43:24 +0200
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Fri, Dec 20, 2019 at 6:17 PM Dan Robertson <dan@dlrobertson.com> wrote:
> >
> > Add a IIO driver for the Bosch BMA400 3-axes ultra-low power accelerometer.
> > The driver supports reading from the acceleration and temperature
> > registers. The driver also supports reading and configuring the output data
> > rate, oversampling ratio, and scale.  
> 
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> One comment below.

Good points below. I've added comments where you suggested.

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

Nice driver. Thanks!

Jonathan

> 
> >
> > Signed-off-by: Dan Robertson <dan@dlrobertson.com>
> > ---
> >  MAINTAINERS                     |   7 +
> >  drivers/iio/accel/Kconfig       |  16 +
> >  drivers/iio/accel/Makefile      |   2 +
> >  drivers/iio/accel/bma400.h      |  95 ++++
> >  drivers/iio/accel/bma400_core.c | 820 ++++++++++++++++++++++++++++++++
> >  drivers/iio/accel/bma400_i2c.c  |  61 +++
> >  6 files changed, 1001 insertions(+)
> >  create mode 100644 drivers/iio/accel/bma400.h
> >  create mode 100644 drivers/iio/accel/bma400_core.c
> >  create mode 100644 drivers/iio/accel/bma400_i2c.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index ec020dc504ca..a5f2cb0de34d 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -3047,6 +3047,13 @@ S:       Supported
> >  F:     drivers/net/bonding/
> >  F:     include/uapi/linux/if_bonding.h
> >
> > +BOSCH SENSORTEC BMA400 ACCELEROMETER IIO DRIVER
> > +M:     Dan Robertson <dan@dlrobertson.com>
> > +L:     linux-iio@vger.kernel.org
> > +S:     Maintained
> > +F:     drivers/iio/accel/bma400*
> > +F:     Documentation/devicetree/bindings/iio/accel/bosch,bma400.yaml
> > +
> >  BPF (Safe dynamic programs and tools)
> >  M:     Alexei Starovoitov <ast@kernel.org>
> >  M:     Daniel Borkmann <daniel@iogearbox.net>
> > diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> > index d4ef35aeb579..670e60568033 100644
> > --- a/drivers/iio/accel/Kconfig
> > +++ b/drivers/iio/accel/Kconfig
> > @@ -112,6 +112,22 @@ config BMA220
> >           To compile this driver as a module, choose M here: the
> >           module will be called bma220_spi.
> >
> > +config BMA400
> > +       tristate "Bosch BMA400 3-Axis Accelerometer Driver"
> > +       select REGMAP
> > +       select BMA400_I2C if I2C
> > +       help
> > +         Say Y here if you want to build a driver for the Bosch BMA400
> > +         triaxial acceleration sensor.
> > +
> > +         To compile this driver as a module, choose M here: the
> > +         module will be called bma400_core and you will also get
> > +         bma400_i2c if I2C is enabled.
> > +
> > +config BMA400_I2C
> > +       tristate
> > +       depends on BMA400
> > +
> >  config BMC150_ACCEL
> >         tristate "Bosch BMC150 Accelerometer Driver"
> >         select IIO_BUFFER
> > diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
> > index 56bd0215e0d4..3a051cf37f40 100644
> > --- a/drivers/iio/accel/Makefile
> > +++ b/drivers/iio/accel/Makefile
> > @@ -14,6 +14,8 @@ obj-$(CONFIG_ADXL372_I2C) += adxl372_i2c.o
> >  obj-$(CONFIG_ADXL372_SPI) += adxl372_spi.o
> >  obj-$(CONFIG_BMA180) += bma180.o
> >  obj-$(CONFIG_BMA220) += bma220_spi.o
> > +obj-$(CONFIG_BMA400) += bma400_core.o
> > +obj-$(CONFIG_BMA400_I2C) += bma400_i2c.o
> >  obj-$(CONFIG_BMC150_ACCEL) += bmc150-accel-core.o
> >  obj-$(CONFIG_BMC150_ACCEL_I2C) += bmc150-accel-i2c.o
> >  obj-$(CONFIG_BMC150_ACCEL_SPI) += bmc150-accel-spi.o
> > diff --git a/drivers/iio/accel/bma400.h b/drivers/iio/accel/bma400.h
> > new file mode 100644
> > index 000000000000..15c0e307d2c4
> > --- /dev/null
> > +++ b/drivers/iio/accel/bma400.h
> > @@ -0,0 +1,95 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Register constants and other forward declarations needed by the bma400
> > + * sources.
> > + *
> > + * Copyright 2019 Dan Robertson <dan@dlrobertson.com>
> > + */
> > +
> > +#ifndef _BMA400_H_
> > +#define _BMA400_H_
> > +
> > +#include <linux/bits.h>
> > +#include <linux/regmap.h>
> > +
> > +/*
> > + * Read-Only Registers
> > + */
> > +
> > +/* Status and ID registers */
> > +#define BMA400_CHIP_ID_REG          0x00
> > +#define BMA400_ERR_REG              0x02
> > +#define BMA400_STATUS_REG           0x03
> > +
> > +/* Acceleration registers */
> > +#define BMA400_X_AXIS_LSB_REG       0x04
> > +#define BMA400_X_AXIS_MSB_REG       0x05
> > +#define BMA400_Y_AXIS_LSB_REG       0x06
> > +#define BMA400_Y_AXIS_MSB_REG       0x07
> > +#define BMA400_Z_AXIS_LSB_REG       0x08
> > +#define BMA400_Z_AXIS_MSB_REG       0x09
> > +
> > +/* Sensor time registers */
> > +#define BMA400_SENSOR_TIME0         0x0a
> > +#define BMA400_SENSOR_TIME1         0x0b
> > +#define BMA400_SENSOR_TIME2         0x0c
> > +
> > +/* Event and interrupt registers */
> > +#define BMA400_EVENT_REG            0x0d
> > +#define BMA400_INT_STAT0_REG        0x0e
> > +#define BMA400_INT_STAT1_REG        0x0f
> > +#define BMA400_INT_STAT2_REG        0x10
> > +
> > +/* Temperature register */
> > +#define BMA400_TEMP_DATA_REG        0x11
> > +
> > +/* FIFO length and data registers */
> > +#define BMA400_FIFO_LENGTH0_REG     0x12
> > +#define BMA400_FIFO_LENGTH1_REG     0x13
> > +#define BMA400_FIFO_DATA_REG        0x14
> > +
> > +/* Step count registers */
> > +#define BMA400_STEP_CNT0_REG        0x15
> > +#define BMA400_STEP_CNT1_REG        0x16
> > +#define BMA400_STEP_CNT3_REG        0x17
> > +#define BMA400_STEP_STAT_REG        0x18
> > +
> > +/*
> > + * Read-write configuration registers
> > + */
> > +#define BMA400_ACC_CONFIG0_REG      0x19
> > +#define BMA400_ACC_CONFIG1_REG      0x1a
> > +#define BMA400_ACC_CONFIG2_REG      0x1b
> > +#define BMA400_CMD_REG              0x7e
> > +
> > +/* Chip ID of BMA 400 devices found in the chip ID register. */
> > +#define BMA400_ID_REG_VAL           0x90
> > +
> > +#define BMA400_LP_OSR_SHIFT         5
> > +#define BMA400_NP_OSR_SHIFT         4
> > +#define BMA400_SCALE_SHIFT          6
> > +
> > +#define BMA400_TWO_BITS_MASK        GENMASK(1, 0)
> > +#define BMA400_LP_OSR_MASK          GENMASK(6, 5)
> > +#define BMA400_NP_OSR_MASK          GENMASK(5, 4)
> > +#define BMA400_ACC_ODR_MASK         GENMASK(3, 0)
> > +#define BMA400_ACC_SCALE_MASK       GENMASK(7, 6)
> > +
> > +#define BMA400_ACC_ODR_MIN_RAW      0x05
> > +#define BMA400_ACC_ODR_LP_RAW       0x06
> > +#define BMA400_ACC_ODR_MAX_RAW      0x0b
> > +
> > +#define BMA400_ACC_ODR_MAX_HZ       800
> > +#define BMA400_ACC_ODR_MIN_WHOLE_HZ 25
> > +#define BMA400_ACC_ODR_MIN_HZ       12
> > +
> > +#define BMA400_SCALE_MIN            38357
> > +#define BMA400_SCALE_MAX            306864
> > +
> > +extern const struct regmap_config bma400_regmap_config;
> > +
> > +int bma400_probe(struct device *dev, struct regmap *regmap, const char *name);
> > +
> > +int bma400_remove(struct device *dev);
> > +
> > +#endif
> > diff --git a/drivers/iio/accel/bma400_core.c b/drivers/iio/accel/bma400_core.c
> > new file mode 100644
> > index 000000000000..e7ba01e79d2c
> > --- /dev/null
> > +++ b/drivers/iio/accel/bma400_core.c
> > @@ -0,0 +1,820 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Core IIO driver for Bosch BMA400 triaxial acceleration sensor.
> > + *
> > + * Copyright 2019 Dan Robertson <dan@dlrobertson.com>
> > + *
> > + * TODO:
> > + *  - Support for power management
> > + *  - Support events and interrupts
> > + *  - Create channel for step count
> > + *  - Create channel for sensor time
> > + */
> > +
> > +#include <linux/bitops.h>
> > +#include <linux/device.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/iio/sysfs.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/mutex.h>
> > +#include <linux/regmap.h>
> > +
> > +#include "bma400.h"
> > +
> > +/*
> > + * The G-range selection may be one of 2g, 4g, 8, or 16g. The scale may
> > + * be selected with the acc_range bits of the ACC_CONFIG1 register.
> > + * NB: This buffer is populated in the device init.
> > + */
> > +static int bma400_scales[8];
> > +
> > +/*
> > + * See the ACC_CONFIG1 section of the datasheet.
> > + * NB: This buffer is populated in the device init.
> > + */
> > +static int bma400_sample_freqs[14];
> > +
> > +static const int bma400_osr_range[] = { 0, 1, 3 };
> > +
> > +/* See the ACC_CONFIG0 section of the datasheet */
> > +enum bma400_power_mode {
> > +       POWER_MODE_SLEEP   = 0x00,
> > +       POWER_MODE_LOW     = 0x01,
> > +       POWER_MODE_NORMAL  = 0x02,
> > +       POWER_MODE_INVALID = 0x03,
> > +};
> > +
> > +struct bma400_sample_freq {
> > +       int hz;
> > +       int uhz;
> > +};
> > +
> > +struct bma400_data {
> > +       struct device *dev;
> > +       struct regmap *regmap;
> > +       struct mutex mutex; /* data register lock */
> > +       struct iio_mount_matrix orientation;
> > +       enum bma400_power_mode power_mode;
> > +       struct bma400_sample_freq sample_freq;
> > +       int oversampling_ratio;
> > +       int scale;
> > +};
> > +
> > +static bool bma400_is_writable_reg(struct device *dev, unsigned int reg)
> > +{
> > +       switch (reg) {
> > +       case BMA400_CHIP_ID_REG:
> > +       case BMA400_ERR_REG:
> > +       case BMA400_STATUS_REG:
> > +       case BMA400_X_AXIS_LSB_REG:
> > +       case BMA400_X_AXIS_MSB_REG:
> > +       case BMA400_Y_AXIS_LSB_REG:
> > +       case BMA400_Y_AXIS_MSB_REG:
> > +       case BMA400_Z_AXIS_LSB_REG:
> > +       case BMA400_Z_AXIS_MSB_REG:
> > +       case BMA400_SENSOR_TIME0:
> > +       case BMA400_SENSOR_TIME1:
> > +       case BMA400_SENSOR_TIME2:
> > +       case BMA400_EVENT_REG:
> > +       case BMA400_INT_STAT0_REG:
> > +       case BMA400_INT_STAT1_REG:
> > +       case BMA400_INT_STAT2_REG:
> > +       case BMA400_TEMP_DATA_REG:
> > +       case BMA400_FIFO_LENGTH0_REG:
> > +       case BMA400_FIFO_LENGTH1_REG:
> > +       case BMA400_FIFO_DATA_REG:
> > +       case BMA400_STEP_CNT0_REG:
> > +       case BMA400_STEP_CNT1_REG:
> > +       case BMA400_STEP_CNT3_REG:
> > +       case BMA400_STEP_STAT_REG:
> > +               return false;
> > +       default:
> > +               return true;
> > +       }
> > +}
> > +
> > +static bool bma400_is_volatile_reg(struct device *dev, unsigned int reg)
> > +{
> > +       switch (reg) {
> > +       case BMA400_ERR_REG:
> > +       case BMA400_STATUS_REG:
> > +       case BMA400_X_AXIS_LSB_REG:
> > +       case BMA400_X_AXIS_MSB_REG:
> > +       case BMA400_Y_AXIS_LSB_REG:
> > +       case BMA400_Y_AXIS_MSB_REG:
> > +       case BMA400_Z_AXIS_LSB_REG:
> > +       case BMA400_Z_AXIS_MSB_REG:
> > +       case BMA400_SENSOR_TIME0:
> > +       case BMA400_SENSOR_TIME1:
> > +       case BMA400_SENSOR_TIME2:
> > +       case BMA400_EVENT_REG:
> > +       case BMA400_INT_STAT0_REG:
> > +       case BMA400_INT_STAT1_REG:
> > +       case BMA400_INT_STAT2_REG:
> > +       case BMA400_TEMP_DATA_REG:
> > +       case BMA400_FIFO_LENGTH0_REG:
> > +       case BMA400_FIFO_LENGTH1_REG:
> > +       case BMA400_FIFO_DATA_REG:
> > +       case BMA400_STEP_CNT0_REG:
> > +       case BMA400_STEP_CNT1_REG:
> > +       case BMA400_STEP_CNT3_REG:
> > +       case BMA400_STEP_STAT_REG:
> > +               return true;
> > +       default:
> > +               return false;
> > +       }
> > +}
> > +
> > +const struct regmap_config bma400_regmap_config = {
> > +       .reg_bits = 8,
> > +       .val_bits = 8,
> > +       .max_register = BMA400_CMD_REG,
> > +       .cache_type = REGCACHE_RBTREE,
> > +       .writeable_reg = bma400_is_writable_reg,
> > +       .volatile_reg = bma400_is_volatile_reg,
> > +};
> > +EXPORT_SYMBOL(bma400_regmap_config);
> > +
> > +static const struct iio_mount_matrix *
> > +bma400_accel_get_mount_matrix(const struct iio_dev *indio_dev,
> > +                             const struct iio_chan_spec *chan)
> > +{
> > +       struct bma400_data *data = iio_priv(indio_dev);
> > +
> > +       return &data->orientation;
> > +}
> > +
> > +static const struct iio_chan_spec_ext_info bma400_ext_info[] = {
> > +       IIO_MOUNT_MATRIX(IIO_SHARED_BY_DIR, bma400_accel_get_mount_matrix),
> > +       { }
> > +};
> > +
> > +#define BMA400_ACC_CHANNEL(_axis) { \
> > +       .type = IIO_ACCEL, \
> > +       .modified = 1, \
> > +       .channel2 = IIO_MOD_##_axis, \
> > +       .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> > +       .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ) | \
> > +               BIT(IIO_CHAN_INFO_SCALE) | \
> > +               BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
> > +       .info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SAMP_FREQ) | \
> > +               BIT(IIO_CHAN_INFO_SCALE) | \
> > +               BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
> > +       .ext_info = bma400_ext_info, \
> > +}
> > +
> > +static const struct iio_chan_spec bma400_channels[] = {
> > +       BMA400_ACC_CHANNEL(X),
> > +       BMA400_ACC_CHANNEL(Y),
> > +       BMA400_ACC_CHANNEL(Z),
> > +       {
> > +               .type = IIO_TEMP,
> > +               .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> > +               .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> > +       },
> > +};
> > +
> > +static int bma400_get_temp_reg(struct bma400_data *data, int *val, int *val2)
> > +{
> > +       unsigned int raw_temp;
> > +       int host_temp;
> > +       int ret;
> > +
> > +       if (data->power_mode == POWER_MODE_SLEEP)
> > +               return -EBUSY;
> > +
> > +       ret = regmap_read(data->regmap, BMA400_TEMP_DATA_REG, &raw_temp);
> > +       if (ret)
> > +               return ret;
> > +
> > +       host_temp = sign_extend32(raw_temp, 7);
> > +       /*
> > +        * The formula for the TEMP_DATA register in the datasheet
> > +        * is: x * 0.5 + 23
> > +        */
> > +       *val = (host_temp >> 1) + 23;
> > +       *val2 = (host_temp & 0x1) * 500000;
> > +       return IIO_VAL_INT_PLUS_MICRO;
> > +}
> > +
> > +static int bma400_get_accel_reg(struct bma400_data *data,
> > +                               const struct iio_chan_spec *chan,
> > +                               int *val)
> > +{
> > +       __le16 raw_accel;
> > +       int lsb_reg;
> > +       int ret;
> > +
> > +       if (data->power_mode == POWER_MODE_SLEEP)
> > +               return -EBUSY;
> > +
> > +       switch (chan->channel2) {
> > +       case IIO_MOD_X:
> > +               lsb_reg = BMA400_X_AXIS_LSB_REG;
> > +               break;
> > +       case IIO_MOD_Y:
> > +               lsb_reg = BMA400_Y_AXIS_LSB_REG;
> > +               break;
> > +       case IIO_MOD_Z:
> > +               lsb_reg = BMA400_Z_AXIS_LSB_REG;
> > +               break;
> > +       default:
> > +               dev_err(data->dev, "invalid axis channel modifier\n");
> > +               return -EINVAL;
> > +       }
> > +
> > +       /* bulk read two registers, with the base being the LSB register */
> > +       ret = regmap_bulk_read(data->regmap, lsb_reg, &raw_accel,
> > +                              sizeof(raw_accel));
> > +       if (ret)
> > +               return ret;
> > +
> > +       *val = sign_extend32(le16_to_cpu(raw_accel), 11);
> > +       return IIO_VAL_INT;
> > +}
> > +
> > +static void bma400_output_data_rate_from_raw(int raw, unsigned int *val,
> > +                                            unsigned int *val2)
> > +{
> > +       *val = BMA400_ACC_ODR_MAX_HZ >> (BMA400_ACC_ODR_MAX_RAW - raw);
> > +       if (raw > BMA400_ACC_ODR_MIN_RAW)
> > +               *val2 = 0;
> > +       else
> > +               *val2 = 500000;
> > +}
> > +
> > +static int bma400_get_accel_output_data_rate(struct bma400_data *data)
> > +{
> > +       unsigned int val;
> > +       unsigned int odr;
> > +       int ret;
> > +
> > +       switch (data->power_mode) {
> > +       case POWER_MODE_LOW:
> > +               /*
> > +                * Runs at a fixed rate in low-power mode. See section 4.3
> > +                * in the datasheet.
> > +                */
> > +               bma400_output_data_rate_from_raw(BMA400_ACC_ODR_LP_RAW,
> > +                                                &data->sample_freq.hz,
> > +                                                &data->sample_freq.uhz);
> > +               return 0;
> > +       case POWER_MODE_NORMAL:
> > +               /*
> > +                * In normal mode the ODR can be found in the ACC_CONFIG1
> > +                * register.
> > +                */
> > +               ret = regmap_read(data->regmap, BMA400_ACC_CONFIG1_REG, &val);
> > +               if (ret)
> > +                       goto error;
> > +
> > +               odr = val & BMA400_ACC_ODR_MASK;
> > +               if (odr < BMA400_ACC_ODR_MIN_RAW ||
> > +                   odr > BMA400_ACC_ODR_MAX_RAW) {
> > +                       ret = -EINVAL;
> > +                       goto error;
> > +               }
> > +
> > +               bma400_output_data_rate_from_raw(odr, &data->sample_freq.hz,
> > +                                                &data->sample_freq.uhz);
> > +               return 0;
> > +       case POWER_MODE_SLEEP:
> > +               data->sample_freq.hz = 0;
> > +               data->sample_freq.uhz = 0;
> > +               return 0;
> > +       default:
> > +               ret = 0;
> > +               goto error;
> > +       }
> > +error:
> > +       data->sample_freq.hz = -1;
> > +       data->sample_freq.uhz = -1;
> > +       return ret;
> > +}
> > +
> > +static int bma400_set_accel_output_data_rate(struct bma400_data *data,
> > +                                            int hz, int uhz)
> > +{
> > +       unsigned int idx;
> > +       unsigned int odr;
> > +       unsigned int val;
> > +       int ret;
> > +
> > +       if (hz >= BMA400_ACC_ODR_MIN_WHOLE_HZ) {
> > +               if (uhz || hz > BMA400_ACC_ODR_MAX_HZ)
> > +                       return -EINVAL;
> > +
> > +               idx = __ffs(hz);
> > +
> > +               if (hz >> idx != BMA400_ACC_ODR_MIN_WHOLE_HZ)  
> 
> Yeah, as I said it works if and only if the MIN_WHOLE_HZ % 2 == 1,
> i.e. odd number.
> Luckily the constant is 25.
> 
> Perhaps it needs a comment somewhere.
> 
> > +                       return -EINVAL;
> > +
> > +               idx += BMA400_ACC_ODR_MIN_RAW + 1;
> > +       } else if (hz == BMA400_ACC_ODR_MIN_HZ && uhz == 500000) {
> > +               idx = BMA400_ACC_ODR_MIN_RAW;
> > +       } else {
> > +               return -EINVAL;
> > +       }
> > +
> > +       ret = regmap_read(data->regmap, BMA400_ACC_CONFIG1_REG, &val);
> > +       if (ret)
> > +               return ret;
> > +
> > +       /* preserve the range and normal mode osr */
> > +       odr = (~BMA400_ACC_ODR_MASK & val) | idx;
> > +
> > +       ret = regmap_write(data->regmap, BMA400_ACC_CONFIG1_REG, odr);
> > +       if (ret)
> > +               return ret;
> > +
> > +       bma400_output_data_rate_from_raw(idx, &data->sample_freq.hz,
> > +                                        &data->sample_freq.uhz);
> > +       return 0;
> > +}
> > +
> > +static int bma400_get_accel_oversampling_ratio(struct bma400_data *data)
> > +{
> > +       unsigned int val;
> > +       unsigned int osr;
> > +       int ret;
> > +
> > +       /*
> > +        * The oversampling ratio is stored in a different register
> > +        * based on the power-mode. In normal mode the OSR is stored
> > +        * in ACC_CONFIG1. In low-power mode it is stored in
> > +        * ACC_CONFIG0.
> > +        */
> > +       switch (data->power_mode) {
> > +       case POWER_MODE_LOW:
> > +               ret = regmap_read(data->regmap, BMA400_ACC_CONFIG0_REG, &val);
> > +               if (ret) {
> > +                       data->oversampling_ratio = -1;
> > +                       return ret;
> > +               }
> > +
> > +               osr = (val & BMA400_LP_OSR_MASK) >> BMA400_LP_OSR_SHIFT;
> > +
> > +               data->oversampling_ratio = osr;
> > +               return 0;
> > +       case POWER_MODE_NORMAL:
> > +               ret = regmap_read(data->regmap, BMA400_ACC_CONFIG1_REG, &val);
> > +               if (ret) {
> > +                       data->oversampling_ratio = -1;
> > +                       return ret;
> > +               }
> > +
> > +               osr = (val & BMA400_NP_OSR_MASK) >> BMA400_NP_OSR_SHIFT;
> > +
> > +               data->oversampling_ratio = osr;
> > +               return 0;
> > +       case POWER_MODE_SLEEP:
> > +               data->oversampling_ratio = 0;
> > +               return 0;
> > +       default:
> > +               data->oversampling_ratio = -1;
> > +               return -EINVAL;
> > +       }
> > +}
> > +
> > +static int bma400_set_accel_oversampling_ratio(struct bma400_data *data,
> > +                                              int val)
> > +{
> > +       unsigned int acc_config;
> > +       int ret;
> > +
> > +       if (val & ~BMA400_TWO_BITS_MASK)
> > +               return -EINVAL;
> > +
> > +       /*
> > +        * The oversampling ratio is stored in a different register
> > +        * based on the power-mode.
> > +        */
> > +       switch (data->power_mode) {
> > +       case POWER_MODE_LOW:
> > +               ret = regmap_read(data->regmap, BMA400_ACC_CONFIG0_REG,
> > +                                 &acc_config);
> > +               if (ret)
> > +                       return ret;
> > +
> > +               ret = regmap_write(data->regmap, BMA400_ACC_CONFIG0_REG,
> > +                                  (acc_config & ~BMA400_LP_OSR_MASK) |
> > +                                  (val << BMA400_LP_OSR_SHIFT));
> > +               if (ret) {
> > +                       dev_err(data->dev, "Failed to write out OSR\n");
> > +                       return ret;
> > +               }
> > +
> > +               data->oversampling_ratio = val;
> > +               return 0;
> > +       case POWER_MODE_NORMAL:
> > +               ret = regmap_read(data->regmap, BMA400_ACC_CONFIG1_REG,
> > +                                 &acc_config);
> > +               if (ret)
> > +                       return ret;
> > +
> > +               ret = regmap_write(data->regmap, BMA400_ACC_CONFIG1_REG,
> > +                                  (acc_config & ~BMA400_NP_OSR_MASK) |
> > +                                  (val << BMA400_NP_OSR_SHIFT));
> > +               if (ret) {
> > +                       dev_err(data->dev, "Failed to write out OSR\n");
> > +                       return ret;
> > +               }
> > +
> > +               data->oversampling_ratio = val;
> > +               return 0;
> > +       default:
> > +               return -EINVAL;
> > +       }
> > +       return ret;
> > +}
> > +
> > +int bma400_accel_scale_to_raw(struct bma400_data *data, unsigned int val)
> > +{
> > +       int raw;
> > +
> > +       if (val == 0)
> > +               return -EINVAL;
> > +
> > +       raw = __ffs(val);
> > +
> > +       if (val >> raw != BMA400_SCALE_MIN)  
> 
> Ditto.
> Luckily it's 38357.
> 
> > +               return -EINVAL;
> > +
> > +       return raw;
> > +}
> > +
> > +static int bma400_get_accel_scale(struct bma400_data *data)
> > +{
> > +       unsigned int raw_scale;
> > +       unsigned int val;
> > +       int ret;
> > +
> > +       ret = regmap_read(data->regmap, BMA400_ACC_CONFIG1_REG, &val);
> > +       if (ret)
> > +               return ret;
> > +
> > +       raw_scale = (val & BMA400_ACC_SCALE_MASK) >> BMA400_SCALE_SHIFT;
> > +       if (raw_scale > BMA400_TWO_BITS_MASK)
> > +               return -EINVAL;
> > +
> > +       data->scale = BMA400_SCALE_MIN << raw_scale;
> > +
> > +       return 0;
> > +}
> > +
> > +static int bma400_set_accel_scale(struct bma400_data *data, unsigned int val)
> > +{
> > +       unsigned int acc_config;
> > +       int raw;
> > +       int ret;
> > +
> > +       ret = regmap_read(data->regmap, BMA400_ACC_CONFIG1_REG, &acc_config);
> > +       if (ret)
> > +               return ret;
> > +
> > +       raw = bma400_accel_scale_to_raw(data, val);
> > +       if (raw < 0)
> > +               return raw;
> > +
> > +       ret = regmap_write(data->regmap, BMA400_ACC_CONFIG1_REG,
> > +                          (acc_config & ~BMA400_ACC_SCALE_MASK) |
> > +                          (raw << BMA400_SCALE_SHIFT));
> > +       if (ret)
> > +               return ret;
> > +
> > +       data->scale = val;
> > +       return 0;
> > +}
> > +
> > +static int bma400_get_power_mode(struct bma400_data *data)
> > +{
> > +       unsigned int val;
> > +       int ret;
> > +
> > +       ret = regmap_read(data->regmap, BMA400_STATUS_REG, &val);
> > +       if (ret) {
> > +               dev_err(data->dev, "Failed to read status register\n");
> > +               return ret;
> > +       }
> > +
> > +       data->power_mode = (val >> 1) & BMA400_TWO_BITS_MASK;
> > +       return 0;
> > +}
> > +
> > +static int bma400_set_power_mode(struct bma400_data *data,
> > +                                enum bma400_power_mode mode)
> > +{
> > +       unsigned int val;
> > +       int ret;
> > +
> > +       ret = regmap_read(data->regmap, BMA400_ACC_CONFIG0_REG, &val);
> > +       if (ret)
> > +               return ret;
> > +
> > +       if (data->power_mode == mode)
> > +               return 0;
> > +
> > +       if (mode == POWER_MODE_INVALID)
> > +               return -EINVAL;
> > +
> > +       /* Preserve the low-power oversample ratio etc */
> > +       ret = regmap_write(data->regmap, BMA400_ACC_CONFIG0_REG,
> > +                          mode | (val & ~BMA400_TWO_BITS_MASK));
> > +       if (ret) {
> > +               dev_err(data->dev, "Failed to write to power-mode\n");
> > +               return ret;
> > +       }
> > +
> > +       data->power_mode = mode;
> > +
> > +       /*
> > +        * Update our cached osr and odr based on the new
> > +        * power-mode.
> > +        */
> > +       bma400_get_accel_output_data_rate(data);
> > +       bma400_get_accel_oversampling_ratio(data);
> > +       return 0;
> > +}
> > +
> > +static void bma400_init_tables(void)
> > +{
> > +       int raw;
> > +       int i;
> > +
> > +       for (i = 0; i + 1 < ARRAY_SIZE(bma400_sample_freqs); i += 2) {
> > +               raw = (i / 2) + 5;
> > +               bma400_output_data_rate_from_raw(raw, &bma400_sample_freqs[i],
> > +                                                &bma400_sample_freqs[i + 1]);
> > +       }
> > +
> > +       for (i = 0; i + 1 < ARRAY_SIZE(bma400_scales); i += 2) {
> > +               raw = i / 2;
> > +               bma400_scales[i] = 0;
> > +               bma400_scales[i + 1] = BMA400_SCALE_MIN << raw;
> > +       }
> > +}
> > +
> > +static int bma400_init(struct bma400_data *data)
> > +{
> > +       unsigned int val;
> > +       int ret;
> > +
> > +       /* Try to read chip_id register. It must return 0x90. */
> > +       ret = regmap_read(data->regmap, BMA400_CHIP_ID_REG, &val);
> > +       if (ret) {
> > +               dev_err(data->dev, "Failed to read chip id register\n");
> > +               goto out;
> > +       }
> > +
> > +       if (val != BMA400_ID_REG_VAL) {
> > +               dev_err(data->dev, "Chip ID mismatch\n");
> > +               ret = -ENODEV;
> > +               goto out;
> > +       }
> > +
> > +       ret = bma400_get_power_mode(data);
> > +       if (ret) {
> > +               dev_err(data->dev, "Failed to get the initial power-mode\n");
> > +               goto out;
> > +       }
> > +
> > +       if (data->power_mode != POWER_MODE_NORMAL) {
> > +               ret = bma400_set_power_mode(data, POWER_MODE_NORMAL);
> > +               if (ret) {
> > +                       dev_err(data->dev, "Failed to wake up the device\n");
> > +                       goto out;
> > +               }
> > +               /*
> > +                * TODO: The datasheet waits 1500us here in the example, but
> > +                * lists 2/ODR as the wakeup time.
> > +                */
> > +               usleep_range(1500, 2000);
> > +       }
> > +
> > +       bma400_init_tables();
> > +
> > +       ret = bma400_get_accel_output_data_rate(data);
> > +       if (ret)
> > +               goto out;
> > +
> > +       ret = bma400_get_accel_oversampling_ratio(data);
> > +       if (ret)
> > +               goto out;
> > +
> > +       ret = bma400_get_accel_scale(data);
> > +       if (ret)
> > +               goto out;
> > +
> > +       /*
> > +        * Once the interrupt engine is supported we might use the
> > +        * data_src_reg, but for now ensure this is set to the
> > +        * variable ODR filter selectable by the sample frequency
> > +        * channel.
> > +        */
> > +       return regmap_write(data->regmap, BMA400_ACC_CONFIG2_REG, 0x00);
> > +
> > +out:
> > +       return ret;
> > +}
> > +
> > +static int bma400_read_raw(struct iio_dev *indio_dev,
> > +                          struct iio_chan_spec const *chan, int *val,
> > +                          int *val2, long mask)
> > +{
> > +       struct bma400_data *data = iio_priv(indio_dev);
> > +       int ret;
> > +
> > +       switch (mask) {
> > +       case IIO_CHAN_INFO_PROCESSED:
> > +               mutex_lock(&data->mutex);
> > +               ret = bma400_get_temp_reg(data, val, val2);
> > +               mutex_unlock(&data->mutex);
> > +               return ret;
> > +       case IIO_CHAN_INFO_RAW:
> > +               mutex_lock(&data->mutex);
> > +               ret = bma400_get_accel_reg(data, chan, val);
> > +               mutex_unlock(&data->mutex);
> > +               return ret;
> > +       case IIO_CHAN_INFO_SAMP_FREQ:
> > +               switch (chan->type) {
> > +               case IIO_ACCEL:
> > +                       if (data->sample_freq.hz < 0)
> > +                               return -EINVAL;
> > +
> > +                       *val = data->sample_freq.hz;
> > +                       *val2 = data->sample_freq.uhz;
> > +                       return IIO_VAL_INT_PLUS_MICRO;
> > +               case IIO_TEMP:
> > +                       /*
> > +                        * Runs at a fixed sampling frequency. See Section 4.4
> > +                        * of the datasheet.
> > +                        */
> > +                       *val = 6;
> > +                       *val2 = 250000;
> > +                       return IIO_VAL_INT_PLUS_MICRO;
> > +               default:
> > +                       return -EINVAL;
> > +               }
> > +       case IIO_CHAN_INFO_SCALE:
> > +               *val = 0;
> > +               *val2 = data->scale;
> > +               return IIO_VAL_INT_PLUS_MICRO;
> > +       case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> > +               /*
> > +                * TODO: We could avoid this logic and returning -EINVAL here if
> > +                * we set both the low-power and normal mode OSR registers when
> > +                * we configure the device.
> > +                */
> > +               if (data->oversampling_ratio < 0)
> > +                       return -EINVAL;
> > +
> > +               *val = data->oversampling_ratio;
> > +               return IIO_VAL_INT;
> > +       default:
> > +               return -EINVAL;
> > +       }
> > +}
> > +
> > +static int bma400_read_avail(struct iio_dev *indio_dev,
> > +                            struct iio_chan_spec const *chan,
> > +                            const int **vals, int *type, int *length,
> > +                            long mask)
> > +{
> > +       switch (mask) {
> > +       case IIO_CHAN_INFO_SCALE:
> > +               *type = IIO_VAL_INT_PLUS_MICRO;
> > +               *vals = bma400_scales;
> > +               *length = ARRAY_SIZE(bma400_scales);
> > +               return IIO_AVAIL_LIST;
> > +       case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> > +               *type = IIO_VAL_INT;
> > +               *vals = bma400_osr_range;
> > +               *length = ARRAY_SIZE(bma400_osr_range);
> > +               return IIO_AVAIL_RANGE;
> > +       case IIO_CHAN_INFO_SAMP_FREQ:
> > +               *type = IIO_VAL_INT_PLUS_MICRO;
> > +               *vals = bma400_sample_freqs;
> > +               *length = ARRAY_SIZE(bma400_sample_freqs);
> > +               return IIO_AVAIL_LIST;
> > +       default:
> > +               return -EINVAL;
> > +       }
> > +}
> > +
> > +static int bma400_write_raw(struct iio_dev *indio_dev,
> > +                           struct iio_chan_spec const *chan, int val, int val2,
> > +                           long mask)
> > +{
> > +       struct bma400_data *data = iio_priv(indio_dev);
> > +       int ret;
> > +
> > +       switch (mask) {
> > +       case IIO_CHAN_INFO_SAMP_FREQ:
> > +               /*
> > +                * The sample frequency is readonly for the temperature
> > +                * register and a fixed value in low-power mode.
> > +                */
> > +               if (chan->type != IIO_ACCEL)
> > +                       return -EINVAL;
> > +
> > +               mutex_lock(&data->mutex);
> > +               ret = bma400_set_accel_output_data_rate(data, val, val2);
> > +               mutex_unlock(&data->mutex);
> > +               return ret;
> > +       case IIO_CHAN_INFO_SCALE:
> > +               if (val != 0 || val2 > BMA400_SCALE_MAX)
> > +                       return -EINVAL;
> > +
> > +               mutex_lock(&data->mutex);
> > +               ret = bma400_set_accel_scale(data, val2);
> > +               mutex_unlock(&data->mutex);
> > +               return ret;
> > +       case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> > +               mutex_lock(&data->mutex);
> > +               ret = bma400_set_accel_oversampling_ratio(data, val);
> > +               mutex_unlock(&data->mutex);
> > +               return ret;
> > +       default:
> > +               return -EINVAL;
> > +       }
> > +}
> > +
> > +static int bma400_write_raw_get_fmt(struct iio_dev *indio_dev,
> > +                                   struct iio_chan_spec const *chan,
> > +                                   long mask)
> > +{
> > +       switch (mask) {
> > +       case IIO_CHAN_INFO_SAMP_FREQ:
> > +               return IIO_VAL_INT_PLUS_MICRO;
> > +       case IIO_CHAN_INFO_SCALE:
> > +               return IIO_VAL_INT_PLUS_MICRO;
> > +       case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> > +               return IIO_VAL_INT;
> > +       default:
> > +               return -EINVAL;
> > +       }
> > +}
> > +
> > +static const struct iio_info bma400_info = {
> > +       .read_raw          = bma400_read_raw,
> > +       .read_avail        = bma400_read_avail,
> > +       .write_raw         = bma400_write_raw,
> > +       .write_raw_get_fmt = bma400_write_raw_get_fmt,
> > +};
> > +
> > +int bma400_probe(struct device *dev, struct regmap *regmap, const char *name)
> > +{
> > +       struct iio_dev *indio_dev;
> > +       struct bma400_data *data;
> > +       int ret;
> > +
> > +       indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> > +       if (!indio_dev)
> > +               return -ENOMEM;
> > +
> > +       data = iio_priv(indio_dev);
> > +       data->regmap = regmap;
> > +       data->dev = dev;
> > +
> > +       ret = bma400_init(data);
> > +       if (ret)
> > +               return ret;
> > +
> > +       ret = iio_read_mount_matrix(dev, "mount-matrix", &data->orientation);
> > +       if (ret)
> > +               return ret;
> > +
> > +       mutex_init(&data->mutex);
> > +       indio_dev->dev.parent = dev;
> > +       indio_dev->name = name;
> > +       indio_dev->info = &bma400_info;
> > +       indio_dev->channels = bma400_channels;
> > +       indio_dev->num_channels = ARRAY_SIZE(bma400_channels);
> > +       indio_dev->modes = INDIO_DIRECT_MODE;
> > +
> > +       dev_set_drvdata(dev, indio_dev);
> > +
> > +       return iio_device_register(indio_dev);
> > +}
> > +EXPORT_SYMBOL(bma400_probe);
> > +
> > +int bma400_remove(struct device *dev)
> > +{
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct bma400_data *data = iio_priv(indio_dev);
> > +       int ret;
> > +
> > +       mutex_lock(&data->mutex);
> > +       ret = bma400_set_power_mode(data, POWER_MODE_SLEEP);
> > +       mutex_unlock(&data->mutex);
> > +
> > +       iio_device_unregister(indio_dev);
> > +
> > +       return ret;
> > +}
> > +EXPORT_SYMBOL(bma400_remove);
> > +
> > +MODULE_AUTHOR("Dan Robertson <dan@dlrobertson.com>");
> > +MODULE_DESCRIPTION("Bosch BMA400 triaxial acceleration sensor core");
> > +MODULE_LICENSE("GPL");
> > diff --git a/drivers/iio/accel/bma400_i2c.c b/drivers/iio/accel/bma400_i2c.c
> > new file mode 100644
> > index 000000000000..9dcb7cc9996e
> > --- /dev/null
> > +++ b/drivers/iio/accel/bma400_i2c.c
> > @@ -0,0 +1,61 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * I2C IIO driver for Bosch BMA400 triaxial acceleration sensor.
> > + *
> > + * Copyright 2019 Dan Robertson <dan@dlrobertson.com>
> > + *
> > + * I2C address is either 0x14 or 0x15 depending on SDO
> > + */
> > +#include <linux/i2c.h>
> > +#include <linux/mod_devicetable.h>
> > +#include <linux/module.h>
> > +#include <linux/regmap.h>
> > +
> > +#include "bma400.h"
> > +
> > +static int bma400_i2c_probe(struct i2c_client *client,
> > +                           const struct i2c_device_id *id)
> > +{
> > +       struct regmap *regmap;
> > +
> > +       regmap = devm_regmap_init_i2c(client, &bma400_regmap_config);
> > +       if (IS_ERR(regmap)) {
> > +               dev_err(&client->dev, "failed to create regmap\n");
> > +               return PTR_ERR(regmap);
> > +       }
> > +
> > +       return bma400_probe(&client->dev, regmap, id->name);
> > +}
> > +
> > +static int bma400_i2c_remove(struct i2c_client *client)
> > +{
> > +       return bma400_remove(&client->dev);
> > +}
> > +
> > +static const struct i2c_device_id bma400_i2c_ids[] = {
> > +       { "bma400", 0 },
> > +       { }
> > +};
> > +MODULE_DEVICE_TABLE(i2c, bma400_i2c_ids);
> > +
> > +static const struct of_device_id bma400_of_i2c_match[] = {
> > +       { .compatible = "bosch,bma400" },
> > +       { }
> > +};
> > +MODULE_DEVICE_TABLE(of, bma400_of_i2c_match);
> > +
> > +static struct i2c_driver bma400_i2c_driver = {
> > +       .driver = {
> > +               .name = "bma400",
> > +               .of_match_table = bma400_of_i2c_match,
> > +       },
> > +       .probe    = bma400_i2c_probe,
> > +       .remove   = bma400_i2c_remove,
> > +       .id_table = bma400_i2c_ids,
> > +};
> > +
> > +module_i2c_driver(bma400_i2c_driver);
> > +
> > +MODULE_AUTHOR("Dan Robertson <dan@dlrobertson.com>");
> > +MODULE_DESCRIPTION("Bosch BMA400 triaxial acceleration sensor (I2C)");
> > +MODULE_LICENSE("GPL");
> >
> >  
> 
>