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Date: Tue, 23 Aug 2016 07:31:38 +0200 (CEST)
From: Peter Meerwald-Stadler <pmeerw@...erw.net>
To: Alison Schofield <amsfield22@...il.com>
cc: jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: adc: ltc2485: add support for Linear Technology
LTC2485 ADC
> 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@...il.com>
> Cc: Daniel Baluta <daniel.baluta@...il.com>
> ---
>
> 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@...il.com>
> + *
> + * 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 = <c2485_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@...il.com>");
> +MODULE_DESCRIPTION("Linear Technology LTC2485 ADC driver");
> +MODULE_LICENSE("GPL v2");
>
--
Peter Meerwald-Stadler
+43-664-2444418 (mobile)
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