Re: [PATCH 1/2] iio: adc: Add MAX1241 driver

Ardelean, Alexandru
2020-03-19T06:51:44Z

On Wed, 2020-03-18 at 22:28 +0200, Alexandru Lazar wrote:
> Add driver for the Maxim MAX1241 12-bit, single-channel ADC. The driver
> includes support for this device's low-power operation mode.

Just one minor typo I see.

>
> Signed-off-by: Alexandru Lazar <alazar@startmail.com>
> ---
> drivers/iio/adc/Kconfig | 10 ++
> drivers/iio/adc/Makefile | 1 +
> drivers/iio/adc/max1241.c | 206 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 217 insertions(+)
> create mode 100644 drivers/iio/adc/max1241.c
>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 5d8540b7b427..4254633147af 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -566,6 +566,16 @@ config MAX1118
> To compile this driver as a module, choose M here: the module will be
> called max1118.
>
> +config MAX1241
> + tristate "Maxim max1241 ADC driver"
> + depends on SPI_MASTER
> + help
> + Say yes here to build support for Maxim max1241 12-bit, single-channel
> + ADC.
> +
> + To compile this driver as a module, choose M here: the module will be
> + called max1118.

Apologies if I did not notice this before. 'called max1118' -> 'called max1241'

> +
> config MAX1363
> tristate "Maxim max1363 ADC driver"
> depends on I2C
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index a1f1fbec0f87..37d6f17559dc 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -54,6 +54,7 @@ obj-$(CONFIG_LTC2497) += ltc2497.o
> obj-$(CONFIG_MAX1027) += max1027.o
> obj-$(CONFIG_MAX11100) += max11100.o
> obj-$(CONFIG_MAX1118) += max1118.o
> +obj-$(CONFIG_MAX1241) += max1241.o
> obj-$(CONFIG_MAX1363) += max1363.o
> obj-$(CONFIG_MAX9611) += max9611.o
> obj-$(CONFIG_MCP320X) += mcp320x.o
> diff --git a/drivers/iio/adc/max1241.c b/drivers/iio/adc/max1241.c
> new file mode 100644
> index 000000000000..0278510ec346
> --- /dev/null
> +++ b/drivers/iio/adc/max1241.c
> @@ -0,0 +1,206 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * MAX1241 low-power, 12-bit serial ADC
> + *
> + * Datasheet:
> https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
> + */
> +
> +#include <linux/regulator/consumer.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +
> +#define MAX1241_VAL_MASK 0xFFF
> +#define MAX1241_SHDN_DELAY_USEC 4
> +
> +enum max1241_id {
> + max1241,
> +};
> +
> +struct max1241 {
> + struct spi_device *spi;
> + struct mutex lock;
> + struct regulator *reg;
> + struct gpio_desc *shdn;
> +
> + __be16 data ____cacheline_aligned;
> +};
> +
> +static const struct iio_chan_spec max1241_channels[] = {
> + {
> + .type = IIO_VOLTAGE,
> + .indexed = 1,
> + .channel = 0,
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> + BIT(IIO_CHAN_INFO_SCALE),
> + .scan_index = 0,
> + .scan_type = {
> + .sign = 'u',
> + .realbits = 12,
> + .storagebits = 16,
> + },
> + },
> +};
> +
> +static int max1241_read(struct max1241 *adc)
> +{
> + struct spi_transfer xfers[] = {
> + /*
> + * Begin conversion by bringing /CS low for at least
> + * tconv us.
> + */
> + {
> + .len = 0,
> + .delay.value = 8,
> + .delay.unit = SPI_DELAY_UNIT_USECS,
> + },
> + /*
> + * Then read two bytes of data in our RX buffer.
> + */
> + {
> + .rx_buf = &adc->data,
> + .len = 2,
> + },
> + };
> +
> + return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
> +}
> +
> +static int max1241_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + int ret, vref_uV;
> + struct max1241 *adc = iio_priv(indio_dev);
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + mutex_lock(&adc->lock);
> +
> + if (adc->shdn) {
> + gpiod_set_value(adc->shdn, 0);
> + udelay(MAX1241_SHDN_DELAY_USEC);
> + }
> +
> + ret = max1241_read(adc);
> +
> + if (adc->shdn)
> + gpiod_set_value(adc->shdn, 1);
> +
> + if (ret) {
> + mutex_unlock(&adc->lock);
> + return ret;
> + }
> +
> + *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;
> +
> + mutex_unlock(&adc->lock);
> + return IIO_VAL_INT;
> + case IIO_CHAN_INFO_SCALE:
> + vref_uV = regulator_get_voltage(adc->reg);
> +
> + if (vref_uV < 0)
> + return vref_uV;
> +
> + *val = vref_uV / 1000;
> + *val2 = 12;
> +
> + return IIO_VAL_FRACTIONAL_LOG2;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static const struct iio_info max1241_info = {
> + .read_raw = max1241_read_raw,
> +};
> +
> +static void max1241_disable_reg_action(void *data)
> +{
> + struct max1241 *adc = data;
> + int err;
> +
> + err = regulator_disable(adc->reg);
> + if (err)
> + dev_err(&adc->spi->dev, "could not disable reference
> regulator.\n");
> +}
> +
> +static int max1241_probe(struct spi_device *spi)
> +{
> + struct iio_dev *indio_dev;
> + struct max1241 *adc;
> + int ret = 0;
> +
> + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
> + if (!indio_dev)
> + return -ENOMEM;
> +
> + adc = iio_priv(indio_dev);
> + adc->spi = spi;
> + mutex_init(&adc->lock);
> +
> + spi_set_drvdata(spi, indio_dev);
> +
> + adc->reg = devm_regulator_get(&spi->dev, "vref");
> + if (IS_ERR(adc->reg)) {
> + dev_err(&spi->dev, "failed to get vref regulator\n");
> + return PTR_ERR(adc->reg);
> + }
> +
> + ret = regulator_enable(adc->reg);
> + if (ret)
> + return ret;
> +
> + ret = devm_add_action_or_reset(&spi->dev, max1241_disable_reg_action,
> + adc);
> + if (ret) {
> + dev_err(&spi->dev, "could not set up regulator cleanup
> action!\n");
> + return ret;
> + }
> +
> + adc->shdn = devm_gpiod_get_optional(&spi->dev, "shdn", GPIOD_OUT_HIGH);
> +
> + if (IS_ERR(adc->shdn))
> + return PTR_ERR(adc->shdn);
> +
> + if (!adc->shdn)
> + dev_dbg(&spi->dev, "no shdn pin passed, low-power mode
> disabled");
> + else
> + dev_dbg(&spi->dev, "shdn pin passed, low-power mode enabled");
> +
> + indio_dev->name = spi_get_device_id(spi)->name;
> + indio_dev->dev.parent = &spi->dev;
> + indio_dev->info = &max1241_info;
> + indio_dev->modes = INDIO_DIRECT_MODE;
> + indio_dev->channels = max1241_channels;
> + indio_dev->num_channels = ARRAY_SIZE(max1241_channels);
> +
> + return devm_iio_device_register(&spi->dev, indio_dev);
> +}
> +
> +static const struct spi_device_id max1241_id[] = {
> + { "max1241", max1241 },
> + {},
> +};
> +
> +static const struct of_device_id max1241_dt_ids[] = {
> + { .compatible = "maxim,max1241" },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, max1241_dt_ids);
> +
> +static struct spi_driver max1241_spi_driver = {
> + .driver = {
> + .name = "max1241",
> + .of_match_table = max1241_dt_ids,
> + },
> + .probe = max1241_probe,
> + .id_table = max1241_id,
> +};
> +module_spi_driver(max1241_spi_driver);
> +
> +MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
> +MODULE_DESCRIPTION("MAX1241 ADC driver");
> +MODULE_LICENSE("GPL v2");