/* * A sensor driver for the magnetometer AK8975. * * Magnetic compass sensor driver for monitoring magnetic flux information. * * Copyright (c) 2010, NVIDIA Corporation. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for * more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ #include #include #include #include #include #include #include #include #include #include /* * Register definitions, as well as various shifts and masks to get at the * individual fields of the registers. */ #define AK8975_REG_WIA 0x00 #define AK8975_DEVICE_ID 0x48 #define AK8975_REG_INFO 0x01 #define AK8975_REG_ST1 0x02 #define AK8975_REG_ST1_DRDY_SHIFT 0 #define AK8975_REG_ST1_DRDY_MASK (1 << AK8975_REG_ST1_DRDY_SHIFT) #define AK8975_REG_HXL 0x03 #define AK8975_REG_HXH 0x04 #define AK8975_REG_HYL 0x05 #define AK8975_REG_HYH 0x06 #define AK8975_REG_HZL 0x07 #define AK8975_REG_HZH 0x08 #define AK8975_REG_ST2 0x09 #define AK8975_REG_ST2_DERR_SHIFT 2 #define AK8975_REG_ST2_DERR_MASK (1 << AK8975_REG_ST2_DERR_SHIFT) #define AK8975_REG_ST2_HOFL_SHIFT 3 #define AK8975_REG_ST2_HOFL_MASK (1 << AK8975_REG_ST2_HOFL_SHIFT) #define AK8975_REG_CNTL 0x0A #define AK8975_REG_CNTL_MODE_SHIFT 0 #define AK8975_REG_CNTL_MODE_MASK (0xF << AK8975_REG_CNTL_MODE_SHIFT) #define AK8975_REG_CNTL_MODE_POWER_DOWN 0 #define AK8975_REG_CNTL_MODE_ONCE 1 #define AK8975_REG_CNTL_MODE_SELF_TEST 8 #define AK8975_REG_CNTL_MODE_FUSE_ROM 0xF #define AK8975_REG_RSVC 0x0B #define AK8975_REG_ASTC 0x0C #define AK8975_REG_TS1 0x0D #define AK8975_REG_TS2 0x0E #define AK8975_REG_I2CDIS 0x0F #define AK8975_REG_ASAX 0x10 #define AK8975_REG_ASAY 0x11 #define AK8975_REG_ASAZ 0x12 #define AK8975_MAX_REGS AK8975_REG_ASAZ /* * Miscellaneous values. */ #define AK8975_MAX_CONVERSION_TIMEOUT 500 #define AK8975_CONVERSION_DONE_POLL_TIME 10 /* * Per-instance context data for the device. */ struct ak8975_data { struct i2c_client *client; struct attribute_group attrs; struct mutex lock; u8 asa[3]; long raw_to_gauss[3]; u8 reg_cache[AK8975_MAX_REGS]; int eoc_gpio; }; static const int ak8975_index_to_reg[] = { AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL, }; /* * Helper function to write to the I2C device's registers. */ static int ak8975_write_data(struct i2c_client *client, u8 reg, u8 val, u8 mask, u8 shift) { struct iio_dev *indio_dev = i2c_get_clientdata(client); struct ak8975_data *data = iio_priv(indio_dev); u8 regval; int ret; regval = (data->reg_cache[reg] & ~mask) | (val << shift); ret = i2c_smbus_write_byte_data(client, reg, regval); if (ret < 0) { dev_err(&client->dev, "Write to device fails status %x\n", ret); return ret; } data->reg_cache[reg] = regval; return 0; } /* * Perform some start-of-day setup, including reading the asa calibration * values and caching them. */ static int ak8975_setup(struct i2c_client *client) { struct iio_dev *indio_dev = i2c_get_clientdata(client); struct ak8975_data *data = iio_priv(indio_dev); u8 device_id; int ret; /* Confirm that the device we're talking to is really an AK8975. */ ret = i2c_smbus_read_byte_data(client, AK8975_REG_WIA); if (ret < 0) { dev_err(&client->dev, "Error reading WIA\n"); return ret; } device_id = ret; if (device_id != AK8975_DEVICE_ID) { dev_err(&client->dev, "Device ak8975 not found\n"); return -ENODEV; } /* Write the fused rom access mode. */ ret = ak8975_write_data(client, AK8975_REG_CNTL, AK8975_REG_CNTL_MODE_FUSE_ROM, AK8975_REG_CNTL_MODE_MASK, AK8975_REG_CNTL_MODE_SHIFT); if (ret < 0) { dev_err(&client->dev, "Error in setting fuse access mode\n"); return ret; } /* Get asa data and store in the device data. */ ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX, 3, data->asa); if (ret < 0) { dev_err(&client->dev, "Not able to read asa data\n"); return ret; } /* After reading fuse ROM data set power-down mode */ ret = ak8975_write_data(client, AK8975_REG_CNTL, AK8975_REG_CNTL_MODE_POWER_DOWN, AK8975_REG_CNTL_MODE_MASK, AK8975_REG_CNTL_MODE_SHIFT); if (ret < 0) { dev_err(&client->dev, "Error in setting power-down mode\n"); return ret; } /* * Precalculate scale factor (in Gauss units) for each axis and * store in the device data. * * This scale factor is axis-dependent, and is derived from 3 calibration * factors ASA(x), ASA(y), and ASA(z). * * These ASA values are read from the sensor device at start of day, and * cached in the device context struct. * * Adjusting the flux value with the sensitivity adjustment value should be * done via the following formula: * * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 ) * * where H is the raw value, ASA is the sensitivity adjustment, and Hadj * is the resultant adjusted value. * * We reduce the formula to: * * Hadj = H * (ASA + 128) / 256 * * H is in the range of -4096 to 4095. The magnetometer has a range of * +-1229uT. To go from the raw value to uT is: * * HuT = H * 1229/4096, or roughly, 3/10. * * Since 1uT = 100 gauss, our final scale factor becomes: * * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100 * Hadj = H * ((ASA + 128) * 30 / 256 * * Since ASA doesn't change, we cache the resultant scale factor into the * device context in ak8975_setup(). */ data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8; data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8; data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8; return 0; } static int wait_conversion_complete_gpio(struct ak8975_data *data) { struct i2c_client *client = data->client; u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT; int ret; /* Wait for the conversion to complete. */ while (timeout_ms) { msleep(AK8975_CONVERSION_DONE_POLL_TIME); if (gpio_get_value(data->eoc_gpio)) break; timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME; } if (!timeout_ms) { dev_err(&client->dev, "Conversion timeout happened\n"); return -EINVAL; } ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1); if (ret < 0) dev_err(&client->dev, "Error in reading ST1\n"); return ret; } static int wait_conversion_complete_polled(struct ak8975_data *data) { struct i2c_client *client = data->client; u8 read_status; u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT; int ret; /* Wait for the conversion to complete. */ while (timeout_ms) { msleep(AK8975_CONVERSION_DONE_POLL_TIME); ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1); if (ret < 0) { dev_err(&client->dev, "Error in reading ST1\n"); return ret; } read_status = ret; if (read_status) break; timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME; } if (!timeout_ms) { dev_err(&client->dev, "Conversion timeout happened\n"); return -EINVAL; } return read_status; } /* * Emits the raw flux value for the x, y, or z axis. */ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val) { struct ak8975_data *data = iio_priv(indio_dev); struct i2c_client *client = data->client; int ret; mutex_lock(&data->lock); /* Set up the device for taking a sample. */ ret = ak8975_write_data(client, AK8975_REG_CNTL, AK8975_REG_CNTL_MODE_ONCE, AK8975_REG_CNTL_MODE_MASK, AK8975_REG_CNTL_MODE_SHIFT); if (ret < 0) { dev_err(&client->dev, "Error in setting operating mode\n"); goto exit; } /* Wait for the conversion to complete. */ if (gpio_is_valid(data->eoc_gpio)) ret = wait_conversion_complete_gpio(data); else ret = wait_conversion_complete_polled(data); if (ret < 0) goto exit; if (ret & AK8975_REG_ST1_DRDY_MASK) { ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2); if (ret < 0) { dev_err(&client->dev, "Error in reading ST2\n"); goto exit; } if (ret & (AK8975_REG_ST2_DERR_MASK | AK8975_REG_ST2_HOFL_MASK)) { dev_err(&client->dev, "ST2 status error 0x%x\n", ret); ret = -EINVAL; goto exit; } } /* Read the flux value from the appropriate register (the register is specified in the iio device attributes). */ ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]); if (ret < 0) { dev_err(&client->dev, "Read axis data fails\n"); goto exit; } mutex_unlock(&data->lock); /* Clamp to valid range. */ *val = clamp_t(s16, ret, -4096, 4095); return IIO_VAL_INT; exit: mutex_unlock(&data->lock); return ret; } static int ak8975_read_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan, int *val, int *val2, long mask) { struct ak8975_data *data = iio_priv(indio_dev); switch (mask) { case IIO_CHAN_INFO_RAW: return ak8975_read_axis(indio_dev, chan->address, val); case IIO_CHAN_INFO_SCALE: *val = data->raw_to_gauss[chan->address]; return IIO_VAL_INT; } return -EINVAL; } #define AK8975_CHANNEL(axis, index) \ { \ .type = IIO_MAGN, \ .modified = 1, \ .channel2 = IIO_MOD_##axis, \ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \ BIT(IIO_CHAN_INFO_SCALE), \ .address = index, \ } static const struct iio_chan_spec ak8975_channels[] = { AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2), }; static const struct iio_info ak8975_info = { .read_raw = &ak8975_read_raw, .driver_module = THIS_MODULE, }; static int ak8975_probe(struct i2c_client *client, const struct i2c_device_id *id) { struct ak8975_data *data; struct iio_dev *indio_dev; int eoc_gpio; int err; /* Grab and set up the supplied GPIO. */ if (client->dev.platform_data == NULL) eoc_gpio = -1; else eoc_gpio = *(int *)(client->dev.platform_data); /* We may not have a GPIO based IRQ to scan, that is fine, we will poll if so */ if (gpio_is_valid(eoc_gpio)) { err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975"); if (err < 0) { dev_err(&client->dev, "failed to request GPIO %d, error %d\n", eoc_gpio, err); goto exit; } } /* Register with IIO */ indio_dev = iio_device_alloc(sizeof(*data)); if (indio_dev == NULL) { err = -ENOMEM; goto exit_gpio; } data = iio_priv(indio_dev); i2c_set_clientdata(client, indio_dev); /* Perform some basic start-of-day setup of the device. */ err = ak8975_setup(client); if (err < 0) { dev_err(&client->dev, "AK8975 initialization fails\n"); goto exit_free_iio; } data->client = client; mutex_init(&data->lock); data->eoc_gpio = eoc_gpio; indio_dev->dev.parent = &client->dev; indio_dev->channels = ak8975_channels; indio_dev->num_channels = ARRAY_SIZE(ak8975_channels); indio_dev->info = &ak8975_info; indio_dev->modes = INDIO_DIRECT_MODE; err = iio_device_register(indio_dev); if (err < 0) goto exit_free_iio; return 0; exit_free_iio: iio_device_free(indio_dev); exit_gpio: if (gpio_is_valid(eoc_gpio)) gpio_free(eoc_gpio); exit: return err; } static int ak8975_remove(struct i2c_client *client) { struct iio_dev *indio_dev = i2c_get_clientdata(client); struct ak8975_data *data = iio_priv(indio_dev); iio_device_unregister(indio_dev); if (gpio_is_valid(data->eoc_gpio)) gpio_free(data->eoc_gpio); iio_device_free(indio_dev); return 0; } static const struct i2c_device_id ak8975_id[] = { {"ak8975", 0}, {} }; MODULE_DEVICE_TABLE(i2c, ak8975_id); static const struct of_device_id ak8975_of_match[] = { { .compatible = "asahi-kasei,ak8975", }, { .compatible = "ak8975", }, { } }; MODULE_DEVICE_TABLE(of, ak8975_of_match); static struct i2c_driver ak8975_driver = { .driver = { .name = "ak8975", .of_match_table = ak8975_of_match, }, .probe = ak8975_probe, .remove = ak8975_remove, .id_table = ak8975_id, }; module_i2c_driver(ak8975_driver); MODULE_AUTHOR("Laxman Dewangan "); MODULE_DESCRIPTION("AK8975 magnetometer driver"); MODULE_LICENSE("GPL");