diff options
Diffstat (limited to 'drivers/iio/adc/ltc2497.c')
| -rw-r--r-- | drivers/iio/adc/ltc2497.c | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c new file mode 100644 index 000000000..e1e14f5d2 --- /dev/null +++ b/drivers/iio/adc/ltc2497.c @@ -0,0 +1,174 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * ltc2497.c - Driver for Analog Devices/Linear Technology LTC2497 ADC + * + * Copyright (C) 2017 Analog Devices Inc. + * + * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf + */ + +#include <linux/i2c.h> +#include <linux/iio/iio.h> +#include <linux/iio/driver.h> +#include <linux/module.h> +#include <linux/mod_devicetable.h> +#include <linux/property.h> + +#include <asm/unaligned.h> + +#include "ltc2497.h" + +enum ltc2497_chip_type { + TYPE_LTC2497, + TYPE_LTC2499, +}; + +struct ltc2497_driverdata { + /* this must be the first member */ + struct ltc2497core_driverdata common_ddata; + struct i2c_client *client; + u32 recv_size; + /* + * DMA (thus cache coherency maintenance) may require the + * transfer buffers to live in their own cache lines. + */ + union { + __be32 d32; + u8 d8[3]; + } data __aligned(IIO_DMA_MINALIGN); +}; + +static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata, + u8 address, int *val) +{ + struct ltc2497_driverdata *st = + container_of(ddata, struct ltc2497_driverdata, common_ddata); + int ret; + + if (val) { + if (st->recv_size == 3) + ret = i2c_master_recv(st->client, (char *)&st->data.d8, + st->recv_size); + else + ret = i2c_master_recv(st->client, (char *)&st->data.d32, + st->recv_size); + if (ret < 0) { + dev_err(&st->client->dev, "i2c_master_recv failed\n"); + return ret; + } + + /* + * The data format is 16/24 bit 2s complement, but with an upper sign bit on the + * resolution + 1 position, which is set for positive values only. Given this + * bit's value, subtracting BIT(resolution + 1) from the ADC's result is + * equivalent to a sign extension. + */ + if (st->recv_size == 3) { + *val = (get_unaligned_be24(st->data.d8) >> 6) + - BIT(ddata->chip_info->resolution + 1); + } else { + *val = (be32_to_cpu(st->data.d32) >> 6) + - BIT(ddata->chip_info->resolution + 1); + } + + /* + * The part started a new conversion at the end of the above i2c + * transfer, so if the address didn't change since the last call + * everything is fine and we can return early. + * If not (which should only happen when some sort of bulk + * conversion is implemented) we have to program the new + * address. Note that this probably fails as the conversion that + * was triggered above is like not complete yet and the two + * operations have to be done in a single transfer. + */ + if (ddata->addr_prev == address) + return 0; + } + + ret = i2c_smbus_write_byte(st->client, + LTC2497_ENABLE | address); + if (ret) + dev_err(&st->client->dev, "i2c transfer failed: %pe\n", + ERR_PTR(ret)); + return ret; +} + +static int ltc2497_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + const struct ltc2497_chip_info *chip_info; + struct iio_dev *indio_dev; + struct ltc2497_driverdata *st; + struct device *dev = &client->dev; + u32 resolution; + + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C | + I2C_FUNC_SMBUS_WRITE_BYTE)) + return -EOPNOTSUPP; + + indio_dev = devm_iio_device_alloc(dev, sizeof(*st)); + if (!indio_dev) + return -ENOMEM; + + st = iio_priv(indio_dev); + i2c_set_clientdata(client, indio_dev); + st->client = client; + st->common_ddata.result_and_measure = ltc2497_result_and_measure; + + chip_info = device_get_match_data(dev); + if (!chip_info) + chip_info = (const struct ltc2497_chip_info *)id->driver_data; + st->common_ddata.chip_info = chip_info; + + resolution = chip_info->resolution; + st->recv_size = BITS_TO_BYTES(resolution) + 1; + + return ltc2497core_probe(dev, indio_dev); +} + +static void ltc2497_remove(struct i2c_client *client) +{ + struct iio_dev *indio_dev = i2c_get_clientdata(client); + + ltc2497core_remove(indio_dev); +} + +static const struct ltc2497_chip_info ltc2497_info[] = { + [TYPE_LTC2497] = { + .resolution = 16, + .name = NULL, + }, + [TYPE_LTC2499] = { + .resolution = 24, + .name = "ltc2499", + }, +}; + +static const struct i2c_device_id ltc2497_id[] = { + { "ltc2497", (kernel_ulong_t)<c2497_info[TYPE_LTC2497] }, + { "ltc2499", (kernel_ulong_t)<c2497_info[TYPE_LTC2499] }, + { } +}; +MODULE_DEVICE_TABLE(i2c, ltc2497_id); + +static const struct of_device_id ltc2497_of_match[] = { + { .compatible = "lltc,ltc2497", .data = <c2497_info[TYPE_LTC2497] }, + { .compatible = "lltc,ltc2499", .data = <c2497_info[TYPE_LTC2499] }, + {}, +}; +MODULE_DEVICE_TABLE(of, ltc2497_of_match); + +static struct i2c_driver ltc2497_driver = { + .driver = { + .name = "ltc2497", + .of_match_table = ltc2497_of_match, + }, + .probe = ltc2497_probe, + .remove = ltc2497_remove, + .id_table = ltc2497_id, +}; +module_i2c_driver(ltc2497_driver); + +MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>"); +MODULE_DESCRIPTION("Linear Technology LTC2497 ADC driver"); +MODULE_LICENSE("GPL v2"); |