Message-ID: <CAEnQRZAyouV1u+Kv5VFXwschVWD7m+sBYhGJ7e392eMg38XiBw@mail.gmail.com>
Date:	Wed, 15 Apr 2015 14:46:22 +0300
From:	Daniel Baluta <daniel.baluta@...el.com>
To:	Peter Meerwald <pmeerw@...erw.net>
Cc:	Daniel Baluta <daniel.baluta@...el.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>
Subject: Re: [PATCH 1/3] iio: magnetometer: Add support for MEMSIC MMC35240 sensor

On Wed, Apr 15, 2015 at 2:28 PM, Peter Meerwald <pmeerw@...erw.net> wrote:
> Hello,
>
> looks good, some comments below...
>
>> Minimal implementation for MMC35240 3-axis magnetometer
>> sensor. It provides processed readings and possiblity to change
>> the sampling frequency.
>
> possibility

Ok.

>
> link to datasheet missing
>

Unfortunately the datasheet isn't public.

>> Signed-off-by: Daniel Baluta <daniel.baluta@...el.com>
>> ---
>>  drivers/iio/magnetometer/Kconfig    |  11 +
>>  drivers/iio/magnetometer/Makefile   |   1 +
>>  drivers/iio/magnetometer/mmc35240.c | 476 ++++++++++++++++++++++++++++++++++++
>>  3 files changed, 488 insertions(+)
>>  create mode 100644 drivers/iio/magnetometer/mmc35240.c
>>
>> diff --git a/drivers/iio/magnetometer/Kconfig b/drivers/iio/magnetometer/Kconfig
>> index a5d6de7..7aba685 100644
>> --- a/drivers/iio/magnetometer/Kconfig
>> +++ b/drivers/iio/magnetometer/Kconfig
>> @@ -47,6 +47,17 @@ config HID_SENSOR_MAGNETOMETER_3D
>>         Say yes here to build support for the HID SENSOR
>>         Magnetometer 3D.
>>
>> +config MMC35240
>> +     tristate "MEMSIC MMC35240 3-axis magnetic sensor"
>> +     select REGMAP_I2C
>> +     depends on I2C
>> +     help
>> +       Say yes here to build support for the MEMSIC MMC35240 3-axis
>> +       magnetic sensor.
>> +
>> +       To compile this driver as a module, choose M here: the module
>> +       will be called mmc35240.
>> +
>>  config IIO_ST_MAGN_3AXIS
>>       tristate "STMicroelectronics magnetometers 3-Axis Driver"
>>       depends on (I2C || SPI_MASTER) && SYSFS
>> diff --git a/drivers/iio/magnetometer/Makefile b/drivers/iio/magnetometer/Makefile
>> index 0f5d3c9..696a429 100644
>> --- a/drivers/iio/magnetometer/Makefile
>> +++ b/drivers/iio/magnetometer/Makefile
>> @@ -6,6 +6,7 @@
>>  obj-$(CONFIG_AK8975) += ak8975.o
>>  obj-$(CONFIG_MAG3110)        += mag3110.o
>>  obj-$(CONFIG_HID_SENSOR_MAGNETOMETER_3D) += hid-sensor-magn-3d.o
>> +obj-$(CONFIG_MMC35240)       += mmc35240.o
>>
>>  obj-$(CONFIG_IIO_ST_MAGN_3AXIS) += st_magn.o
>>  st_magn-y := st_magn_core.o
>> diff --git a/drivers/iio/magnetometer/mmc35240.c b/drivers/iio/magnetometer/mmc35240.c
>> new file mode 100644
>> index 0000000..c46c1f7
>> --- /dev/null
>> +++ b/drivers/iio/magnetometer/mmc35240.c
>> @@ -0,0 +1,476 @@
>> +/*
>> + * MMC35240 - MEMSIC 3-axis Magnetic Sensor
>> + *
>> + * Copyright (c) 2015, Intel Corporation.
>> + *
>> + * This file is subject to the terms and conditions of version 2 of
>> + * the GNU General Public License.  See the file COPYING in the main
>> + * directory of this archive for more details.
>> + *
>> + * IIO driver for MMC35240 (7-bit I2C slave address 0x30).
>> + *
>> + * TODO: offset, ACPI, continuous measurement mode, PM
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/init.h>
>> +#include <linux/i2c.h>
>> +#include <linux/delay.h>
>> +#include <linux/regmap.h>
>> +
>> +#include <linux/iio/iio.h>
>> +#include <linux/iio/sysfs.h>
>> +
>> +#define MMC35240_DRV_NAME "mmc35240"
>> +#define MMC35240_REGMAP_NAME "mmc35240_regmap"
>> +
>> +#define MMC35240_REG_XOUT_L  0x00
>> +#define MMC35240_REG_XOUT_H  0x01
>> +#define MMC35240_REG_YOUT_L  0x02
>> +#define MMC35240_REG_YOUT_H  0x03
>> +#define MMC35240_REG_ZOUT_L  0x04
>> +#define MMC35240_REG_ZOUT_H  0x05
>> +
>> +#define MMC35240_REG_STATUS  0x06
>> +#define MMC35240_REG_CTRL0   0x07
>> +#define MMC35240_REG_CTRL1   0x08
>> +
>> +#define MMC35240_REG_ID              0x20
>> +
>> +#define MMC35240_STATUS_MEAS_DONE_BIT        BIT(0)
>> +
>> +#define MMC35240_CTRL0_REFILL_BIT    BIT(7)
>> +#define MMC35240_CTRL0_RESET_BIT     BIT(6)
>> +#define MMC35240_CTRL0_SET_BIT               BIT(5)
>> +#define MMC35240_CTRL0_CMM_BIT               BIT(1)
>> +#define MMC35240_CTRL0_TM_BIT                BIT(0)
>> +
>> +/* output resolution bits */
>> +#define MMC35240_CTRL1_BW0_BIT               BIT(0)
>> +#define MMC35240_CTRL1_BW1_BIT               BIT(1)
>> +
>> +#define MMC35240_CTRL1_BW_MASK        (MMC35240_CTRL1_BW0_BIT | \
>> +              MMC35240_CTRL1_BW1_BIT)
>> +#define MMC35240_CTRL1_BW_SHIFT              0
>> +
>> +#define MMC35240_WAIT_CHARGE_PUMP    50000   /* us */
>> +#define MMC53240_WAIT_SET_RESET              1000    /* us */
>> +
>> +enum mmc35240_resolution {
>> +     MMC35240_16_BITS_SLOW = 0, /* 100 Hz */
>> +     MMC35240_16_BITS_FAST,     /* 200 Hz */
>> +     MMC35240_14_BITS,          /* 333 Hz */
>> +     MMC35240_12_BITS,          /* 666 Hz */
>> +     MMC35240_MAX_BITS /* this must be last */
>
> _MAX_BITS is not used

Will remove. Very likely, at the moment of coding this I thought of some sort
of enumeration on all possible resolutions.

>
>> +};
>> +
>> +enum mmc35240_axis {
>> +     AXIS_X = 0,
>> +     AXIS_Y,
>> +     AXIS_Z,
>> +};
>> +
>> +static const struct {
>> +     int sens[3]; /* sensitivity per X, Y, Z axis */
>> +     int nfo; /* null field output */
>> +} mmc35240_props_table[] = {
>> +     /* 16 bits, 100Hz ODR */
>> +     {
>> +             {1024, 1024, 770},
>> +             32768,
>> +     },
>> +     /* 16 bits, 200Hz ODR */
>> +     {
>> +             {1024, 1024, 770},
>> +             32768,
>> +     },
>> +     /* 14 bits, 333Hz ODR */
>> +     {
>> +             {256, 256, 193},
>> +             8192,
>> +     },
>> +     /* 12 bits, 666Hz ODR */
>> +     {
>> +             {64, 64, 48},
>> +             2048,
>> +     },
>> +};
>> +
>> +struct mmc35240_data {
>> +     struct i2c_client *client;
>> +     struct mutex mutex;
>> +     struct regmap *regmap;
>> +     enum mmc35240_resolution res;
>> +};
>> +
>> +int mmc35240_samp_freq[] = {100, 200, 333, 666};
>> +
>> +static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("100 200 333 666");
>> +
>> +#define MMC35240_CHANNEL(_axis) { \
>> +     .type = IIO_MAGN, \
>> +     .modified = 1, \
>> +     .channel2 = IIO_MOD_ ## _axis, \
>> +     .address = AXIS_ ## _axis, \
>> +     .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
>> +     .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ), \
>> +}
>> +
>> +static const struct iio_chan_spec mmc35240_channels[] = {
>> +     MMC35240_CHANNEL(X),
>> +     MMC35240_CHANNEL(Y),
>> +     MMC35240_CHANNEL(Z),
>> +};
>> +
>> +static struct attribute *mmc35240_attributes[] = {
>> +     &iio_const_attr_sampling_frequency_available.dev_attr.attr,
>> +};
>> +
>> +static const struct attribute_group mmc35240_attribute_group = {
>> +     .attrs = mmc35240_attributes,
>> +};
>> +
>> +static int mmc35240_get_samp_freq_index(struct mmc35240_data *data,
>> +                                     int val, int val2)
>> +{
>> +     int i;
>> +
>> +     for (i = 0; i < ARRAY_SIZE(mmc35240_samp_freq); i++)
>> +             if (mmc35240_samp_freq[i] == val)
>> +                     return i;
>> +     return -EINVAL;
>> +}
>> +
>> +static int mmc35240_hw_set(struct mmc35240_data *data, bool set)
>> +{
>> +     int ret;
>> +     u8 coil_bit;
>> +
>> +     /*
>> +      * Recharge the capacitor at VCAP pin, requested to be issued
>> +      * before a SET/RESET command.
>> +      */
>> +     ret = regmap_update_bits(data->regmap, MMC35240_REG_CTRL0,
>> +                              MMC35240_CTRL0_REFILL_BIT,
>> +                              MMC35240_CTRL0_REFILL_BIT);
>> +     if (ret < 0)
>> +             return ret;
>> +     usleep_range(MMC35240_WAIT_CHARGE_PUMP, MMC35240_WAIT_CHARGE_PUMP + 1);
>> +
>> +     if (set)
>> +             coil_bit = MMC35240_CTRL0_SET_BIT;
>> +     else
>> +             coil_bit = MMC35240_CTRL0_RESET_BIT;
>> +
>> +     return regmap_update_bits(data->regmap, MMC35240_REG_CTRL0,
>> +                               MMC35240_CTRL0_REFILL_BIT,
>> +                               coil_bit);
>> +}
>> +
>> +static int mmc35240_init(struct mmc35240_data *data)
>> +{
>> +     int ret;
>> +     unsigned int reg_id;
>> +
>> +     ret = regmap_read(data->regmap, MMC35240_REG_ID, &reg_id);
>> +     if (ret < 0) {
>> +             dev_err(&data->client->dev, "Error reading product id\n");
>> +             return ret;
>> +     }
>> +
>> +     dev_info(&data->client->dev, "MMC35240 chip id %x\n", reg_id);
>
> better check the ID and avoid cluttering the log

Hmm, ok. I've seen drivers with both versions. Perhaps dev_dbg instead
of dev_info?
Anyhow, will change in v2.

>
>> +
>> +     /*
>> +      * make sure we restore sensor characteristics, by doing
>> +      * a RESET/SET sequence
>> +      */
>> +     ret = mmc35240_hw_set(data, false);
>> +     if (ret < 0)
>> +             return ret;
>> +     usleep_range(MMC53240_WAIT_SET_RESET, MMC53240_WAIT_SET_RESET + 1);
>> +
>> +     ret = mmc35240_hw_set(data, true);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     /* set default sampling frequency */
>> +     return regmap_update_bits(data->regmap, MMC35240_REG_CTRL1,
>> +                               MMC35240_CTRL1_BW_MASK,
>> +                               data->res << MMC35240_CTRL1_BW_SHIFT);
>> +}
>> +
>> +static int mmc35240_take_measurement(struct mmc35240_data *data)
>> +{
>> +     int ret, tries = 100;
>> +     unsigned int reg_status;
>
> reg_status is probably a u8?
>
>> +
>> +     ret = regmap_write(data->regmap, MMC35240_REG_CTRL0,
>> +                        MMC35240_CTRL0_TM_BIT);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     while (tries-- > 0) {
>> +             ret = regmap_read(data->regmap, MMC35240_REG_STATUS,
>> +                               &reg_status);
>> +             if (ret < 0)
>> +                     return ret;
>> +             if (reg_status & MMC35240_STATUS_MEAS_DONE_BIT)
>> +                     break;
>> +             msleep(20);
>> +     }
>> +
>> +     if (tries < 0) {
>> +             dev_err(&data->client->dev, "data not ready\n");
>> +             return -EIO;
>> +     }
>> +
>> +     return 0;
>> +}
>> +
>> +static int mmc35240_read_measurement(struct mmc35240_data *data, __le16 buf[3])
>> +{
>> +     int ret;
>> +
>> +     ret = mmc35240_take_measurement(data);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     return regmap_bulk_read(data->regmap, MMC35240_REG_XOUT_L, (u8 *)buf,
>> +                             3 * sizeof(__be16));
>
> sizeof(__le16)

Correct.

>
>> +}
>> +
>> +int mmc35240_raw_to_gauss(struct mmc35240_data *data, int index, __le16 buf[],
>> +                       int *val, int *val2)
>> +{
>> +     int raw_x, raw_y, raw_z;
>> +     int sens_x, sens_y, sens_z;
>> +     int nfo;
>> +
>> +     raw_x = le16_to_cpu(buf[AXIS_X]);
>> +     raw_y = le16_to_cpu(buf[AXIS_Y]);
>> +     raw_z = le16_to_cpu(buf[AXIS_Z]);
>> +
>> +     sens_x = mmc35240_props_table[data->res].sens[AXIS_X];
>> +     sens_y = mmc35240_props_table[data->res].sens[AXIS_Y];
>> +     sens_z = mmc35240_props_table[data->res].sens[AXIS_Z];
>> +
>> +     nfo = mmc35240_props_table[data->res].nfo;
>> +
>> +     switch (index) {
>> +     case AXIS_X:
>
> I'd rather expose a _RAW with _SCALE/_OFFSET

This is was also my intention at a first glance. But if you look on
computation of Y or Z axis
processed value you'll see that this is not possible.

Processed value for Y depends on raw_y, raw_z, sensitivity_y,
sensitivity_z and offset.
Any idea on how to expose this as _RAW with _SCALE/_OFFSET is welcomed.

>
>> +             *val = (raw_x - nfo) / sens_x;
>> +             *val2 = ((raw_x - nfo) % sens_x) * 1000000;
>> +             break;
>> +     case AXIS_Y:
>> +             *val = (raw_y - nfo) / sens_y - (raw_z - nfo) / sens_z;
>> +             *val2 = (((raw_y - nfo) % sens_y - (raw_z - nfo) % sens_z))
>> +                     * 1000000;
>> +             break;
>> +     case AXIS_Z:
>> +             *val = (raw_y - nfo) / sens_y + (raw_z - nfo) / sens_z;
>> +             *val2 = (((raw_y - nfo) % sens_y + (raw_z - nfo) % sens_z))
>> +                     * 1000000;
>> +             break;
>> +     default:
>> +             return -EINVAL;
>> +     }
>> +     return 0;
>> +}
>> +
>> +static int mmc35240_read_raw(struct iio_dev *indio_dev,
>> +                          struct iio_chan_spec const *chan, int *val,
>> +                          int *val2, long mask)
>> +{
>> +     struct mmc35240_data *data = iio_priv(indio_dev);
>> +     int ret, i;
>> +     unsigned int reg;
>
> reg is u8 probably

regmap_read needs the third parameter (reg in our case) to be unsigned int.

>
>> +     __le16 buf[3];
>> +
>> +     switch (mask) {
>> +     case IIO_CHAN_INFO_PROCESSED:
>> +             mutex_lock(&data->mutex);
>> +             ret = mmc35240_read_measurement(data, buf);
>> +             mutex_unlock(&data->mutex);
>> +             if (ret < 0)
>> +                     return ret;
>> +             ret = mmc35240_raw_to_gauss(data, chan->address,
>> +                                         buf, val, val2);
>> +             if (ret < 0)
>> +                     return ret;
>> +             return IIO_VAL_INT_PLUS_MICRO;
>> +     case IIO_CHAN_INFO_SAMP_FREQ:
>> +             mutex_lock(&data->mutex);
>> +             ret = regmap_read(data->regmap, MMC35240_REG_CTRL1, &reg);
>> +             mutex_unlock(&data->mutex);
>> +             if (ret < 0)
>> +                     return ret;
>> +
>> +             i = (reg & MMC35240_CTRL1_BW_MASK) >> MMC35240_CTRL1_BW_SHIFT;
>> +             if (i < 0 || i > ARRAY_SIZE(mmc35240_samp_freq))
>
>>= ARRAY_SIZE
>
>> +                     return -EINVAL;
>> +
>> +             *val = mmc35240_samp_freq[i];
>> +             *val2 = 0;
>> +             return IIO_VAL_INT_PLUS_MICRO;
>
> return IIO_VAL_INT

Ok.

>
>> +     default:
>> +             return -EINVAL;
>> +     }
>> +}
>> +
>> +static int mmc35240_write_raw(struct iio_dev *indio_dev,
>> +                           struct iio_chan_spec const *chan, int val,
>> +                           int val2, long mask)
>> +{
>> +     struct mmc35240_data *data = iio_priv(indio_dev);
>> +     int i, ret;
>> +
>> +     switch (mask) {
>> +     case IIO_CHAN_INFO_SAMP_FREQ:
>> +             i = mmc35240_get_samp_freq_index(data, val, val2);
>> +             if (i < 0)
>> +                     return -EINVAL;
>> +             mutex_lock(&data->mutex);
>> +             ret = regmap_update_bits(data->regmap, MMC35240_REG_CTRL1,
>> +                                      MMC35240_CTRL1_BW_MASK,
>> +                                      i << MMC35240_CTRL1_BW_SHIFT);
>> +             mutex_unlock(&data->mutex);
>> +             return ret;
>> +     default:
>> +             return -EINVAL;
>> +     }
>> +}
>> +
>> +static const struct iio_info mmc35240_info = {
>> +     .driver_module  = THIS_MODULE,
>> +     .read_raw       = mmc35240_read_raw,
>> +     .write_raw      = mmc35240_write_raw,
>> +     .attrs          = &mmc35240_attribute_group,
>> +};
>> +
>> +static bool mmc35240_is_writeable_reg(struct device *dev, unsigned int reg)
>> +{
>> +     switch (reg) {
>> +     case MMC35240_REG_CTRL0:
>> +     case MMC35240_REG_CTRL1:
>> +             return true;
>> +     default:
>> +             return false;
>> +     }
>> +}
>> +
>> +static bool mmc35240_is_readable_reg(struct device *dev, unsigned int reg)
>> +{
>> +     switch (reg) {
>> +     case MMC35240_REG_XOUT_L:
>> +     case MMC35240_REG_XOUT_H:
>> +     case MMC35240_REG_YOUT_L:
>> +     case MMC35240_REG_YOUT_H:
>> +     case MMC35240_REG_ZOUT_L:
>> +     case MMC35240_REG_ZOUT_H:
>> +     case MMC35240_REG_STATUS:
>> +     case MMC35240_REG_ID:
>> +             return true;
>> +     default:
>> +             return false;
>> +     }
>> +}
>> +
>> +static bool mmc35240_is_volatile_reg(struct device *dev, unsigned int reg)
>> +{
>> +     switch (reg) {
>> +     case MMC35240_REG_CTRL0:
>> +     case MMC35240_REG_CTRL1:
>> +             return false;
>> +     default:
>> +             return true;
>> +     }
>> +}
>> +
>> +static struct reg_default mmc35240_reg_defaults[] = {
>> +     { MMC35240_REG_CTRL0,  0x00 },
>> +     { MMC35240_REG_CTRL1,  0x00 },
>> +};
>> +
>> +static const struct regmap_config mmc35240_regmap_config = {
>> +     .name = MMC35240_REGMAP_NAME,
>> +
>> +     .reg_bits = 8,
>> +     .val_bits = 8,
>> +
>> +     .max_register = MMC35240_REG_ID,
>> +     .cache_type = REGCACHE_FLAT,
>> +
>> +     .writeable_reg = mmc35240_is_writeable_reg,
>> +     .readable_reg = mmc35240_is_readable_reg,
>> +     .volatile_reg = mmc35240_is_volatile_reg,
>> +
>> +     .reg_defaults = mmc35240_reg_defaults,
>> +     .num_reg_defaults = ARRAY_SIZE(mmc35240_reg_defaults),
>> +};
>> +
>> +static int mmc35240_probe(struct i2c_client *client,
>> +                       const struct i2c_device_id *id)
>> +{
>> +     struct mmc35240_data *data;
>> +     struct iio_dev *indio_dev;
>> +     struct regmap *regmap;
>> +     int ret;
>> +
>> +     indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
>> +     if (!indio_dev)
>> +             return -ENOMEM;
>> +
>> +     regmap = devm_regmap_init_i2c(client, &mmc35240_regmap_config);
>> +     if (IS_ERR(regmap)) {
>> +             dev_err(&client->dev, "regmap initialization failed\n");
>> +             return PTR_ERR(regmap);
>> +     }
>> +
>> +     data = iio_priv(indio_dev);
>> +     i2c_set_clientdata(client, indio_dev);
>> +     data->client = client;
>> +     data->regmap = regmap;
>> +     data->res = MMC35240_16_BITS_SLOW;
>> +
>> +     mutex_init(&data->mutex);
>> +
>> +     indio_dev->dev.parent = &client->dev;
>> +     indio_dev->info = &mmc35240_info;
>> +     indio_dev->name = MMC35240_DRV_NAME;
>> +     indio_dev->channels = mmc35240_channels;
>> +     indio_dev->num_channels = ARRAY_SIZE(mmc35240_channels);
>> +     indio_dev->modes = INDIO_DIRECT_MODE;
>> +
>> +     ret = mmc35240_init(data);
>> +     if (ret < 0) {
>> +             dev_err(&client->dev, "mmc35240 chip init failed\n");
>> +             return ret;
>> +     }
>> +     return devm_iio_device_register(&client->dev, indio_dev);
>> +}
>> +
>> +static int mmc35240_remove(struct i2c_client *client)
>> +{
>
> no need for this function (yet)

So this means I can remove it from mmc35240_driver struct definition?
Will do.

>
>> +     return 0;
>> +}
>> +
>> +static const struct i2c_device_id mmc35240_id[] = {
>> +     {"MMC35240", 0},
>> +     {}
>> +};
>> +MODULE_DEVICE_TABLE(i2c, mmc35240_id);
>> +
>> +static struct i2c_driver mmc35240_driver = {
>> +     .driver = {
>> +             .name = MMC35240_DRV_NAME,
>> +     },
>> +     .probe          = mmc35240_probe,
>> +     .remove         = mmc35240_remove,
>> +     .id_table       = mmc35240_id,
>> +};
>> +
>> +module_i2c_driver(mmc35240_driver);
>> +
>> +MODULE_AUTHOR("Daniel Baluta <daniel.baluta@...el.com>");
>> +MODULE_DESCRIPTION("MEMSIC MMC35240 magnetic sensor driver");
>> +MODULE_LICENSE("GPL v2");
>>
>

Thanks a lot Peter for your comments. I will leave this here for
others to have a look and send v2 in few days.

Daniel.
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