Date:   Sun, 2 Apr 2017 10:30:31 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     michael.hennerich@...log.com, lars@...afoo.de, knaack.h@....de,
        pmeerw@...erw.net, robh+dt@...nel.org, mark.rutland@....com
Cc:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio:adc: Driver for Linear Technology LTC2497 ADC

On 27/03/17 08:23, michael.hennerich@...log.com wrote:
> From: Michael Hennerich <michael.hennerich@...log.com>
> 
> This patch adds support for the Analog Devices / Linear Technology
> LTC2497 ADCs. The LTC2497 is a 16-channel (eight differential),
> 16-bit, high precision, delta-sigma ADC with an automatic, differential,
> input current cancellation front end and a 2-wire, I2C interface.
> 
> Signed-off-by: Michael Hennerich <michael.hennerich@...log.com>
Looks good to me.

Applied to the togreg branch of iio.git and pushed out as testing for
the autobuilders to play with it.

Bindings are trivial so happy to take without pestering Rob or Mark.
(of course their comments are always welcome!)

Thanks,

Jonathan
> 
> ---
> 
> Changes since v1:
> 
>  - remove confusing kconfig help text
>  - use proper defines
>  - add descriptive comment
>  - fix removal order
>  - add poper commit mssage
> ---
>  .../devicetree/bindings/iio/adc/ltc2497.txt        |  13 +
>  MAINTAINERS                                        |   1 +
>  drivers/iio/adc/Kconfig                            |  10 +
>  drivers/iio/adc/Makefile                           |   1 +
>  drivers/iio/adc/ltc2497.c                          | 269 +++++++++++++++++++++
>  5 files changed, 294 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/ltc2497.txt
>  create mode 100644 drivers/iio/adc/ltc2497.c
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/ltc2497.txt b/Documentation/devicetree/bindings/iio/adc/ltc2497.txt
> new file mode 100644
> index 0000000..c2829c19
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/ltc2497.txt
> @@ -0,0 +1,13 @@
> +* Linear Technology / Analog Devices LTC2497 ADC
> +
> +Required properties:
> + - compatible: Should be "lltc,ltc2497"
> + - reg: Should contain the ADC I2C address
> + - vref-supply: The regulator supply for ADC reference voltage
> +
> +Example:
> +	ltc2497: adc@76 {
> +		compatible = "lltc,ltc2497";
> +		reg = <0x76>;
> +		vref-supply = <&ltc2497_reg>;
> +	};
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a7d6f9a..173043c 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -813,6 +813,7 @@ W:	http://wiki.analog.com/
>  W:	http://ez.analog.com/community/linux-device-drivers
>  S:	Supported
>  F:	drivers/iio/*/ad*
> +F:	drivers/iio/adc/ltc2497*
>  X:	drivers/iio/*/adjd*
>  F:	drivers/staging/iio/*/ad*
>  F:	drivers/staging/iio/trigger/iio-trig-bfin-timer.c
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 2268a6f..acc115b 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -326,6 +326,16 @@ config LTC2485
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called ltc2485.
>  
> +config LTC2497
> +	tristate "Linear Technology LTC2497 ADC driver"
> +	depends on I2C
> +	help
> +	  Say yes here to build support for Linear Technology LTC2497
> +	  16-Bit 8-/16-Channel Delta Sigma ADC.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called ltc2497.
> +
>  config MAX1027
>  	tristate "Maxim max1027 ADC driver"
>  	depends on SPI
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 73dbe39..9d626b5 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -32,6 +32,7 @@ obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
>  obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
>  obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
>  obj-$(CONFIG_LTC2485) += ltc2485.o
> +obj-$(CONFIG_LTC2497) += ltc2497.o
>  obj-$(CONFIG_MAX1027) += max1027.o
>  obj-$(CONFIG_MAX11100) += max11100.o
>  obj-$(CONFIG_MAX1363) += max1363.o
> diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c
> new file mode 100644
> index 0000000..7907534
> --- /dev/null
> +++ b/drivers/iio/adc/ltc2497.c
> @@ -0,0 +1,269 @@
> +/*
> + * ltc2497.c - Driver for Linear Technology LTC2497 ADC
> + *
> + * Copyright (C) 2017 Analog Devices Inc.
> + *
> + * Licensed under the GPL-2.
> + *
> + * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf
> + */
> +
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/delay.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/of.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +#define LTC2497_ENABLE			0xA0
> +#define LTC2497_SGL			(1 << 4)
> +#define LTC2497_DIFF			(0 << 4)
> +#define LTC2497_SIGN			(1 << 3)
> +#define LTC2497_CONFIG_DEFAULT		LTC2497_ENABLE
> +#define LTC2497_CONVERSION_TIME_MS	150ULL
> +
> +struct ltc2497_st {
> +	struct i2c_client *client;
> +	struct regulator *ref;
> +	ktime_t	time_prev;
> +	u8 addr_prev;
> +};
> +
> +static int ltc2497_wait_conv(struct ltc2497_st *st)
> +{
> +	s64 time_elapsed;
> +
> +	time_elapsed = ktime_ms_delta(ktime_get(), st->time_prev);
> +
> +	if (time_elapsed < LTC2497_CONVERSION_TIME_MS) {
> +		/* delay if conversion time not passed
> +		 * since last read or write
> +		 */
> +		msleep(LTC2497_CONVERSION_TIME_MS - time_elapsed);
> +		return 0;
> +	}
> +
> +	if (time_elapsed - LTC2497_CONVERSION_TIME_MS <= 0) {
> +		/* We're in automatic mode -
> +		 * so the last reading is stil not outdated
> +		 */
> +		return 0;
> +	}
> +
> +	return -ETIMEDOUT;
> +}
> +
> +static int ltc2497_read(struct ltc2497_st *st, u8 address, int *val)
> +{
> +	struct i2c_client *client = st->client;
> +	__be32 buf = 0;
> +	int ret;
> +
> +	ret = ltc2497_wait_conv(st);
> +	if (ret < 0 || st->addr_prev != address) {
> +		ret = i2c_smbus_write_byte(st->client,
> +					   LTC2497_ENABLE | address);
> +		if (ret < 0)
> +			return ret;
> +		st->addr_prev = address;
> +		msleep(LTC2497_CONVERSION_TIME_MS);
> +	}
> +	ret = i2c_master_recv(client, (char *)&buf, 3);
> +	if (ret < 0)  {
> +		dev_err(&client->dev, "i2c_master_recv failed\n");
> +		return ret;
> +	}
> +	st->time_prev = ktime_get();
> +
> +	/* convert and shift the result,
> +	 * and finally convert from offset binary to signed integer
> +	 */
> +	*val = (be32_to_cpu(buf) >> 14) - (1 << 17);
> +
> +	return ret;
> +}
> +
> +static int ltc2497_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct ltc2497_st *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&indio_dev->mlock);
> +		ret = ltc2497_read(st, chan->address, val);
> +		mutex_unlock(&indio_dev->mlock);
> +		if (ret < 0)
> +			return ret;
> +
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		ret = regulator_get_voltage(st->ref);
> +		if (ret < 0)
> +			return ret;
> +
> +		*val = ret / 1000;
> +		*val2 = 17;
> +
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +#define LTC2497_CHAN(_chan, _addr) { \
> +	.type = IIO_VOLTAGE, \
> +	.indexed = 1, \
> +	.channel = (_chan), \
> +	.address = (_addr | (_chan / 2) | ((_chan & 1) ? LTC2497_SIGN : 0)), \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> +}
> +
> +#define LTC2497_CHAN_DIFF(_chan, _addr) { \
> +	.type = IIO_VOLTAGE, \
> +	.indexed = 1, \
> +	.channel = (_chan) * 2 + ((_addr) & LTC2497_SIGN ? 1 : 0), \
> +	.channel2 = (_chan) * 2 + ((_addr) & LTC2497_SIGN ? 0 : 1),\
> +	.address = (_addr | _chan), \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> +	.differential = 1, \
> +}
> +
> +static const struct iio_chan_spec ltc2497_channel[] = {
> +	LTC2497_CHAN(0, LTC2497_SGL),
> +	LTC2497_CHAN(1, LTC2497_SGL),
> +	LTC2497_CHAN(2, LTC2497_SGL),
> +	LTC2497_CHAN(3, LTC2497_SGL),
> +	LTC2497_CHAN(4, LTC2497_SGL),
> +	LTC2497_CHAN(5, LTC2497_SGL),
> +	LTC2497_CHAN(6, LTC2497_SGL),
> +	LTC2497_CHAN(7, LTC2497_SGL),
> +	LTC2497_CHAN(8, LTC2497_SGL),
> +	LTC2497_CHAN(9, LTC2497_SGL),
> +	LTC2497_CHAN(10, LTC2497_SGL),
> +	LTC2497_CHAN(11, LTC2497_SGL),
> +	LTC2497_CHAN(12, LTC2497_SGL),
> +	LTC2497_CHAN(13, LTC2497_SGL),
> +	LTC2497_CHAN(14, LTC2497_SGL),
> +	LTC2497_CHAN(15, LTC2497_SGL),
> +	LTC2497_CHAN_DIFF(0, LTC2497_DIFF),
> +	LTC2497_CHAN_DIFF(1, LTC2497_DIFF),
> +	LTC2497_CHAN_DIFF(2, LTC2497_DIFF),
> +	LTC2497_CHAN_DIFF(3, LTC2497_DIFF),
> +	LTC2497_CHAN_DIFF(4, LTC2497_DIFF),
> +	LTC2497_CHAN_DIFF(5, LTC2497_DIFF),
> +	LTC2497_CHAN_DIFF(6, LTC2497_DIFF),
> +	LTC2497_CHAN_DIFF(7, LTC2497_DIFF),
> +	LTC2497_CHAN_DIFF(0, LTC2497_DIFF | LTC2497_SIGN),
> +	LTC2497_CHAN_DIFF(1, LTC2497_DIFF | LTC2497_SIGN),
> +	LTC2497_CHAN_DIFF(2, LTC2497_DIFF | LTC2497_SIGN),
> +	LTC2497_CHAN_DIFF(3, LTC2497_DIFF | LTC2497_SIGN),
> +	LTC2497_CHAN_DIFF(4, LTC2497_DIFF | LTC2497_SIGN),
> +	LTC2497_CHAN_DIFF(5, LTC2497_DIFF | LTC2497_SIGN),
> +	LTC2497_CHAN_DIFF(6, LTC2497_DIFF | LTC2497_SIGN),
> +	LTC2497_CHAN_DIFF(7, LTC2497_DIFF | LTC2497_SIGN),
> +};
> +
> +static const struct iio_info ltc2497_info = {
> +	.read_raw = ltc2497_read_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static int ltc2497_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct iio_dev *indio_dev;
> +	struct ltc2497_st *st;
> +	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(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	st->client = client;
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->name = id->name;
> +	indio_dev->info = &ltc2497_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = ltc2497_channel;
> +	indio_dev->num_channels = ARRAY_SIZE(ltc2497_channel);
> +
> +	st->ref = devm_regulator_get(&client->dev, "vref");
> +	if (IS_ERR(st->ref))
> +		return PTR_ERR(st->ref);
> +
> +	ret = regulator_enable(st->ref);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = i2c_smbus_write_byte(st->client, LTC2497_CONFIG_DEFAULT);
> +	if (ret < 0)
> +		goto err_regulator_disable;
> +
> +	st->addr_prev = LTC2497_CONFIG_DEFAULT;
> +	st->time_prev = ktime_get();
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret < 0)
> +		goto err_regulator_disable;
> +
> +	return 0;
> +
> +err_regulator_disable:
> +	regulator_disable(st->ref);
> +
> +	return ret;
> +}
> +
> +static int ltc2497_remove(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct ltc2497_st *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +	regulator_disable(st->ref);
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id ltc2497_id[] = {
> +	{ "ltc2497", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, ltc2497_id);
> +
> +static const struct of_device_id ltc2497_of_match[] = {
> +	{ .compatible = "lltc,ltc2497", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, ltc2497_of_match);
> +
> +static struct i2c_driver ltc2497_driver = {
> +	.driver = {
> +		.name = "ltc2497",
> +		.of_match_table = of_match_ptr(ltc2497_of_match),
> +	},
> +	.probe = ltc2497_probe,
> +	.remove = ltc2497_remove,
> +	.id_table = ltc2497_id,
> +};
> +module_i2c_driver(ltc2497_driver);
> +
> +MODULE_AUTHOR("Michael Hennerich <michael.hennerich@...log.com>");
> +MODULE_DESCRIPTION("Linear Technology LTC2497 ADC driver");
> +MODULE_LICENSE("GPL v2");
> 

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