Re: [PATCH] iio: adc: ltc2485: add support for Linear Technology LTC2485 ADC

[Peter Meerwald-Stadler]

> Adds basic support for the LTC2485 ADC - a delta-sigma analog-to-digital
> converter with an I2C interface that operates in single shot conversion
> mode. 

comments below, looks good
 
> The driver supports an on board 5V reference and the power-on default
> configuration which rejects both 50hz & 60hz line frequencies and
> operates in 1x speed mode.
> 
> Signed-off-by: Alison Schofield <amsfield22@xxxxxxxxx>
> Cc: Daniel Baluta <daniel.baluta@xxxxxxxxx>
> ---
> 
> Reviewers: In addition to commenting on what is present, please comment
> on what is absent and the priority in which you would like to see
> additional features added to this driver, or needed in this first submittal.
> 
> Not supported: 
> 1. External Vref
> 2. Additional Configuration Modes
>         Temperature Sensor Mode: report temp data (not voltage).
> 
>         Line Frequency Rejection Mode: select to reject 50Hz or 60Hz
> 	or both. (both is default)
> 
>         Speed Mode: Default speed mode (1x) performs two conversions each
> 	cycle and combines the results.  2x speed mode only does one
> 	conversion each cycle.
> 3. Power management
> 4. DT Bindings
> 5. Triggered buffers
> 6. What else?
> 
> 
>  drivers/iio/adc/Kconfig   |   9 +++
>  drivers/iio/adc/Makefile  |   1 +
>  drivers/iio/adc/ltc2485.c | 150 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 160 insertions(+)
>  create mode 100644 drivers/iio/adc/ltc2485.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 1de31bd..a042611 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -264,6 +264,15 @@ config LPC18XX_ADC
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called lpc18xx_adc.
>  
> +config LTC2485
> +	tristate "Linear Technology LTC2485 ADC driver"
> +	depends on I2C
> +	help
> +	  Say yes here to build support for Linear Technology LTC2485 ADC.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called ltc2485.
> +
>  config MAX1027
>  	tristate "Maxim max1027 ADC driver"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 0ba0d50..1be5747 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -27,6 +27,7 @@ obj-$(CONFIG_IMX7D_ADC) += imx7d_adc.o
>  obj-$(CONFIG_INA2XX_ADC) += ina2xx-adc.o
>  obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
>  obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
> +obj-$(CONFIG_LTC2485) += ltc2485.o
>  obj-$(CONFIG_MAX1027) += max1027.o
>  obj-$(CONFIG_MAX1363) += max1363.o
>  obj-$(CONFIG_MCP320X) += mcp320x.o
> diff --git a/drivers/iio/adc/ltc2485.c b/drivers/iio/adc/ltc2485.c
> new file mode 100644
> index 0000000..a62778b
> --- /dev/null
> +++ b/drivers/iio/adc/ltc2485.c
> @@ -0,0 +1,150 @@
> +/*
> + * ltc2485.c - Driver for Linear Technology LTC2485 ADC
> + *
> + * Copyright (C) 2016 Alison Schofield <amsfield22@xxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * Datasheet: http://cds.linear.com/docs/en/datasheet/2485fd.pdf
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +/* Power-on configuration: rejects both 50/60Hz, operates at 1x speed */
> +#define LTC2485_CONFIG_DEFAULT		0
> +
> +struct ltc2485_data {
> +	struct i2c_client	*client;
> +	s64			time_prev;	/* last conversion */
> +};
> +
> +static void ltc2485_wait_conv(struct ltc2485_data *data)
> +{
> +	int conv_time = 147000000;		/* conv time ns */

const maybe?

> +	s64 time_elapsed;
> +
> +	/* delay if conversion time not passed since last read or write */
> +	time_elapsed = ktime_get_real_ns() - data->time_prev;
> +
> +	if (time_elapsed < conv_time) {
> +		usleep_range((conv_time - time_elapsed) / 1000,
> +			     conv_time / 1000);
> +	}
> +}
> +
> +static int ltc2485_read(struct ltc2485_data *data, int *val)
> +{
> +	struct i2c_client *client = data->client;
> +	__be32 buf = 0;
> +	int ret;
> +
> +	ltc2485_wait_conv(data);
> +
> +	ret = i2c_master_recv(client, (char *)&buf, 4);
> +	if (ret < 0)  {
> +		dev_err(&client->dev, "i2c_master_recv failed\n");
> +		return ret;
> +	}
> +
> +	data->time_prev = ktime_get_real_ns();
> +	*val = sign_extend32(be32_to_cpu(buf) >> 6, 24);
> +
> +	return ret;
> +}
> +
> +static int ltc2485_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct ltc2485_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (mask == IIO_CHAN_INFO_RAW) {
> +		ret = ltc2485_read(data, val);
> +		if (ret < 0)
> +			return ret;
> +
> +		return IIO_VAL_INT;
> +
> +	} else if (mask == IIO_CHAN_INFO_SCALE) {
> +		*val = 5000;			/* on board vref millivolts */
> +		*val2 = 25;			/* 25 (24 + sign) data bits */
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +
> +	} else {
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_chan_spec ltc2485_channel[] = {
> +	{
> +		.type = IIO_VOLTAGE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE)
> +	},
> +};
> +
> +static const struct iio_info ltc2485_info = {
> +	.read_raw = ltc2485_read_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static int ltc2485_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct iio_dev *indio_dev;
> +	struct ltc2485_data *data;
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
> +				     I2C_FUNC_SMBUS_WRITE_BYTE))
> +		return -EOPNOTSUPP;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	data->client = client;
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->name = id->name;
> +	indio_dev->info = &ltc2485_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = ltc2485_channel;
> +	indio_dev->num_channels = ARRAY_SIZE(ltc2485_channel);
> +
> +	ret = i2c_smbus_write_byte(data->client, LTC2485_CONFIG_DEFAULT);
> +	if (ret < 0)
> +		return ret;
> +
> +	data->time_prev = ktime_get_real_ns();
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id ltc2485_id[] = {
> +	{ "ltc2485", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, ltc2485_id);
> +
> +static struct i2c_driver ltc2485_driver = {
> +	.driver = {
> +		.name = "ltc2485",
> +	},
> +	.probe = ltc2485_probe,
> +	.id_table = ltc2485_id,
> +};
> +module_i2c_driver(ltc2485_driver);
> +
> +MODULE_AUTHOR("Alison Schofield <amsfield22@xxxxxxxxx>");
> +MODULE_DESCRIPTION("Linear Technology LTC2485 ADC driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald-Stadler
+43-664-2444418 (mobile)