Date:   Thu, 23 Mar 2017 15:45:40 +0100
From:   Michael Hennerich <michael.hennerich@...log.com>
To:     Peter Meerwald-Stadler <pmeerw@...erw.net>
CC:     <jic23@...nel.org>, <lars@...afoo.de>, <knaack.h@....de>,
        <robh+dt@...nel.org>, <mark.rutland@....com>,
        <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio/adc/ltc2497: Driver for Linear Technology LTC2497 ADC

On 23.03.2017 12:28, Peter Meerwald-Stadler wrote:
> On Thu, 23 Mar 2017, michael.hennerich@...log.com wrote:
>
>> From: Michael Hennerich <michael.hennerich@...log.com>
>
> comments below

Hi Peter,

Thanks for the review -
comments inline.

>
>> Signed-off-by: Michael Hennerich <michael.hennerich@...log.com>
>> ---
>>  .../devicetree/bindings/iio/adc/ltc2497.txt        |  13 +
>>  MAINTAINERS                                        |   1 +
>>  drivers/iio/adc/Kconfig                            |  11 +
>>  drivers/iio/adc/Makefile                           |   1 +
>>  drivers/iio/adc/ltc2497.c                          | 263 +++++++++++++++++++++
>>  5 files changed, 289 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..141cf4a 100644
>> --- a/drivers/iio/adc/Kconfig
>> +++ b/drivers/iio/adc/Kconfig
>> @@ -326,6 +326,17 @@ 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.
>> +	  Provides direct access via sysfs
>
> the line "Provides..." should be removed I think, it confuses me at least

Sure I can remove - originally added to make checkpatch happy.

>
>> +
>> +	  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..0452715
>> --- /dev/null
>> +++ b/drivers/iio/adc/ltc2497.c
>> @@ -0,0 +1,263 @@
>> +/*
>> + * 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
>
> is the ULL really needed?

Needed? - maybe not - but probably not wrong ktime_ms_delta() returns 
64bit and we later do some comparisons...

>
>> +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, 0xA0 | address);
>
> use LTC2497_ENABLE instead of 0xa0

good catch.

>
>> +		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();
>> +	*val = (be32_to_cpu(buf) >> 14) - (1 << 17);
>
> what is the purpose of - (1 << 17)? maybe add a comment?
> I'd rather do it with bit operations that arithmetic

Well - this is for offset binary to signed conversion.
I'll add a comment.

>
>> +
>> +	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 = devm_iio_device_register(&client->dev, indio_dev);
>
> no devm_ since we have a non-empty _remove()?

ok

>
>> +	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);
>> +
>> +	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");
>>
>


-- 
Greetings,
Michael

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