diff options
Diffstat (limited to 'drivers/iio/adc/max11100.c')
| -rw-r--r-- | drivers/iio/adc/max11100.c | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/drivers/iio/adc/max11100.c b/drivers/iio/adc/max11100.c new file mode 100644 index 000000000..49e38dca8 --- /dev/null +++ b/drivers/iio/adc/max11100.c @@ -0,0 +1,163 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * iio/adc/max11100.c + * Maxim max11100 ADC Driver with IIO interface + * + * Copyright (C) 2016-17 Renesas Electronics Corporation + * Copyright (C) 2016-17 Jacopo Mondi + */ +#include <linux/delay.h> +#include <linux/kernel.h> +#include <linux/mod_devicetable.h> +#include <linux/module.h> +#include <linux/regulator/consumer.h> +#include <linux/spi/spi.h> +#include <asm/unaligned.h> + +#include <linux/iio/iio.h> +#include <linux/iio/driver.h> + +/* + * LSB is the ADC single digital step + * 1 LSB = (vref_mv / 2 ^ 16) + * + * LSB is used to calculate analog voltage value + * from the number of ADC steps count + * + * Ain = (count * LSB) + */ +#define MAX11100_LSB_DIV (1 << 16) + +struct max11100_state { + struct regulator *vref_reg; + struct spi_device *spi; + + /* + * DMA (thus cache coherency maintenance) may require the + * transfer buffers to live in their own cache lines. + */ + u8 buffer[3] __aligned(IIO_DMA_MINALIGN); +}; + +static const struct iio_chan_spec max11100_channels[] = { + { /* [0] */ + .type = IIO_VOLTAGE, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | + BIT(IIO_CHAN_INFO_SCALE), + }, +}; + +static int max11100_read_single(struct iio_dev *indio_dev, int *val) +{ + int ret; + struct max11100_state *state = iio_priv(indio_dev); + + ret = spi_read(state->spi, state->buffer, sizeof(state->buffer)); + if (ret) { + dev_err(&indio_dev->dev, "SPI transfer failed\n"); + return ret; + } + + /* the first 8 bits sent out from ADC must be 0s */ + if (state->buffer[0]) { + dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n"); + return -EINVAL; + } + + *val = get_unaligned_be16(&state->buffer[1]); + + return 0; +} + +static int max11100_read_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + int *val, int *val2, long info) +{ + int ret, vref_uv; + struct max11100_state *state = iio_priv(indio_dev); + + switch (info) { + case IIO_CHAN_INFO_RAW: + ret = max11100_read_single(indio_dev, val); + if (ret) + return ret; + + return IIO_VAL_INT; + + case IIO_CHAN_INFO_SCALE: + vref_uv = regulator_get_voltage(state->vref_reg); + if (vref_uv < 0) + /* dummy regulator "get_voltage" returns -EINVAL */ + return -EINVAL; + + *val = vref_uv / 1000; + *val2 = MAX11100_LSB_DIV; + return IIO_VAL_FRACTIONAL; + } + + return -EINVAL; +} + +static const struct iio_info max11100_info = { + .read_raw = max11100_read_raw, +}; + +static void max11100_regulator_disable(void *reg) +{ + regulator_disable(reg); +} + +static int max11100_probe(struct spi_device *spi) +{ + int ret; + struct iio_dev *indio_dev; + struct max11100_state *state; + + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state)); + if (!indio_dev) + return -ENOMEM; + + state = iio_priv(indio_dev); + state->spi = spi; + + indio_dev->name = "max11100"; + indio_dev->info = &max11100_info; + indio_dev->modes = INDIO_DIRECT_MODE; + indio_dev->channels = max11100_channels; + indio_dev->num_channels = ARRAY_SIZE(max11100_channels); + + state->vref_reg = devm_regulator_get(&spi->dev, "vref"); + if (IS_ERR(state->vref_reg)) + return PTR_ERR(state->vref_reg); + + ret = regulator_enable(state->vref_reg); + if (ret) + return ret; + + ret = devm_add_action_or_reset(&spi->dev, max11100_regulator_disable, + state->vref_reg); + if (ret) + return ret; + + return devm_iio_device_register(&spi->dev, indio_dev); +} + +static const struct of_device_id max11100_ids[] = { + {.compatible = "maxim,max11100"}, + { }, +}; +MODULE_DEVICE_TABLE(of, max11100_ids); + +static struct spi_driver max11100_driver = { + .driver = { + .name = "max11100", + .of_match_table = max11100_ids, + }, + .probe = max11100_probe, +}; + +module_spi_driver(max11100_driver); + +MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>"); +MODULE_DESCRIPTION("Maxim max11100 ADC Driver"); +MODULE_LICENSE("GPL v2"); |