Message-ID: <20170924154547.15e932b4@archlinux>
Date:   Sun, 24 Sep 2017 15:45:47 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     "Ismail H. Kose" <Ismail.Kose@...imintegrated.com>
Cc:     ihkose@...il.com, Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mike Looijmans <mike.looijmans@...ic.nl>,
        Peter Rosin <peda@...ntia.se>,
        Fabrice Gasnier <fabrice.gasnier@...com>,
        Maxime Roussin-Belanger <maxime.roussinbelanger@...il.com>,
        Jean-Francois Dagenais <jeff.dagenais@...il.com>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/2] iio: dac: ds4422/ds4424 dac driver

On Fri, 22 Sep 2017 13:12:08 -0700
"Ismail H. Kose" <Ismail.Kose@...imintegrated.com> wrote:

> This patch provides an iio device driver for DS4422/DS4424 chips that support
> two/four channel 7-bit Sink/Source Current DAC.
> 
> Signed-off-by: Ismail H. Kose <Ismail.Kose@...imintegrated.com>
> Signed-off-by: Ismail H. Kose <ihkose@...il.com>

A few minor comments inline.  This is coming together nicely.

Jonathan

> ---
> v6:
> 	* Removed reference resistor parsing
> v5:
> 	* Removed unused variable
> v4:
> 	* Removed unnecessary code and space optimization
> 	* Alphabetic order in Kconfig and Makefile
> v3:
> 	* Removed iio-map and platform file support
> 	* Removed ds4424.h file
> 	* Fixed ADC value read bug
> 	* Removed confused comments
> 	* Added device tree binding file
> 	* Fixed bugs in probe and read function
> v2:
> 	* Fixed coding style and removed unncessary code
> 	* Removed min/max rfs, ifs-scale, etc values from device tree
> 	* Removed unused code, definitions and some comments
> 	* Removed regulator control and made standard structure
> 	* Removed data processing and channel scale
> 	* Removed device tree binding file
> 
>  drivers/iio/dac/Kconfig  |   9 ++
>  drivers/iio/dac/Makefile |   1 +
>  drivers/iio/dac/ds4424.c | 340 +++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 350 insertions(+)
>  create mode 100644 drivers/iio/dac/ds4424.c
> 
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index 25bed2d7d2b9..57c179830981 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -211,6 +211,15 @@ config AD8801
>  	  To compile this driver as a module choose M here: the module will be called
>  	  ad8801.
>  
> +config DS4424
> +	tristate "Maxim Integrated DS4422/DS4424 DAC driver"
> +	depends on I2C
> +	help
> +	  If you say yes here you get support for Maxim chips DS4422, DS4424.
> +
> +	  This driver can also be built as a module.  If so, the module
> +	  will be called ds4424.
> +
>  config DPOT_DAC
>  	tristate "DAC emulation using a DPOT"
>  	depends on OF
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index 603587cc2f07..abf5c3094454 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -22,6 +22,7 @@ obj-$(CONFIG_AD5686) += ad5686.o
>  obj-$(CONFIG_AD7303) += ad7303.o
>  obj-$(CONFIG_AD8801) += ad8801.o
>  obj-$(CONFIG_CIO_DAC) += cio-dac.o
> +obj-$(CONFIG_DS4424) += ds4424.o
>  obj-$(CONFIG_DPOT_DAC) += dpot-dac.o
>  obj-$(CONFIG_LPC18XX_DAC) += lpc18xx_dac.o
>  obj-$(CONFIG_LTC2632) += ltc2632.o
> diff --git a/drivers/iio/dac/ds4424.c b/drivers/iio/dac/ds4424.c
> new file mode 100644
> index 000000000000..aea0cd12f9b8
> --- /dev/null
> +++ b/drivers/iio/dac/ds4424.c
> @@ -0,0 +1,340 @@
> +/*
> + * Maxim Integrated
> + * 7-bit, Multi-Channel Sink/Source Current DAC Driver
> + * Copyright (C) 2017 Maxim Integrated
> + *
> + * 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.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/err.h>
> +#include <linux/delay.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/driver.h>
> +#include <linux/iio/machine.h>
> +#include <linux/iio/consumer.h>
> +
> +#define DS4422_MAX_DAC_CHANNELS		2
> +#define DS4424_MAX_DAC_CHANNELS		4
> +
> +#define DS4424_DAC_ADDR(chan)   ((chan) + 0xf8)
> +#define DS4424_SOURCE_I		1
> +#define DS4424_SINK_I		0
> +
> +#define DS4424_CHANNEL(chan) { \
> +	.type = IIO_CURRENT, \
> +	.indexed = 1, \
> +	.output = 1, \
> +	.channel = chan, \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> +}
> +
> +/*
> + * DS4424 DAC control register 8 bits
> + * [7]		0: to sink; 1: to source
> + * [6:0]	steps to sink/source
> + * bit[7] looks like a sign bit, but the value of the register is
> + * not a two's complement code considering the bit[6:0] is a absolute
> + * distance from the zero point.
> + */
> +union ds4424_raw_data {
> +	struct {
> +		u8 dx:7;
> +		u8 source_bit:1;
> +	};
> +	u8 bits;
> +};
> +
> +enum ds4424_device_ids {
> +	ID_DS4422,
> +	ID_DS4424,
> +};
> +
> +struct ds4424_data {
> +	struct i2c_client *client;
> +	struct mutex lock;
> +	__maybe_unused uint8_t save[DS4424_MAX_DAC_CHANNELS];
> +	struct regulator *vcc_reg;
> +	uint8_t raw[DS4424_MAX_DAC_CHANNELS];
> +};
> +
> +static const struct iio_chan_spec ds4424_channels[] = {
> +	DS4424_CHANNEL(0),
> +	DS4424_CHANNEL(1),
> +	DS4424_CHANNEL(2),
> +	DS4424_CHANNEL(3),
> +};
> +
> +static int ds4424_get_value(struct iio_dev *indio_dev,
> +			     int *val, int channel)
> +{
> +	struct ds4424_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&data->lock);
> +	ret = i2c_smbus_read_byte_data(data->client, DS4424_DAC_ADDR(channel));
> +	if (ret < 0)
> +		goto fail;
> +
> +	*val = ret;
> +	mutex_unlock(&data->lock);
> +	return 0;

Lose previous two lines and use the logic in the error path.

> +
> +fail:
> +	mutex_unlock(&data->lock);
> +	return ret;
> +}
> +
> +static int ds4424_set_value(struct iio_dev *indio_dev,
> +			     int val, struct iio_chan_spec const *chan)
> +{
> +	struct ds4424_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&data->lock);
> +	ret = i2c_smbus_write_byte_data(data->client,
> +			DS4424_DAC_ADDR(chan->channel), val);
> +	if (ret < 0) {
> +		mutex_unlock(&data->lock);

A goto unlock: would be slightly cleaner.

> +		return ret;
> +	}
> +
> +	data->raw[chan->channel] = val;
> +	mutex_unlock(&data->lock);
> +
> +	return 0;
> +}
> +
> +static int ds4424_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long mask)
> +{
> +	union ds4424_raw_data raw;
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = ds4424_get_value(indio_dev, val, chan->channel);
> +		if (ret < 0) {
> +			pr_err("%s : ds4424_get_value returned %d\n",
> +							__func__, ret);
> +			return ret;
> +		}
> +		raw.bits = *val;
> +		*val = raw.dx;
> +		if (raw.source_bit == DS4424_SINK_I)
> +			*val = -*val;
> +		return IIO_VAL_INT;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ds4424_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int val, int val2, long mask)
> +{
> +	union ds4424_raw_data raw;
> +
> +	if (val2 != 0)
> +		return -EINVAL;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (val < S8_MIN || val > S8_MAX)
> +			return -EINVAL;
> +
> +		if (val > 0) {
> +			raw.source_bit = DS4424_SOURCE_I;
> +			raw.dx = val;
> +		} else {
> +			raw.source_bit = DS4424_SINK_I;
> +			raw.dx = -val;
> +		}
> +
> +		return ds4424_set_value(indio_dev, raw.bits, chan);
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ds4424_verify_chip(struct iio_dev *indio_dev)
> +{
> +	int ret, val;
> +
> +	ret = ds4424_get_value(indio_dev, &val, DS4424_DAC_ADDR(0));
> +	if (ret < 0)
> +		dev_err(&indio_dev->dev,
> +				"%s failed. ret: %d\n", __func__, ret);
> +
> +	return ret;
> +}
> +
> +static int __maybe_unused ds4424_suspend(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct ds4424_data *data = iio_priv(indio_dev);
> +	int ret = 0;
> +	int i;
> +
> +	for (i = 0; i < indio_dev->num_channels; i++) {
> +		data->save[i] = data->raw[i];
> +		ret = ds4424_set_value(indio_dev, 0,
> +				&indio_dev->channels[i]);
> +		if (ret < 0)
> +			return ret;
> +	}
> +	return ret;
> +}
> +
> +static int __maybe_unused ds4424_resume(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct ds4424_data *data = iio_priv(indio_dev);
> +	int ret = 0;
> +	int i;
> +
> +	for (i = 0; i < indio_dev->num_channels; i++) {
> +		ret = ds4424_set_value(indio_dev, data->save[i],
> +				&indio_dev->channels[i]);
> +		if (ret < 0)
> +			return ret;
> +	}
> +	return ret;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(ds4424_pm_ops, ds4424_suspend, ds4424_resume);
> +
> +static const struct iio_info ds4424_info = {
> +	.read_raw = ds4424_read_raw,
> +	.write_raw = ds4424_write_raw,
> +};
> +
> +static int ds4424_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct ds4424_data *data;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev) {
> +		dev_err(&client->dev, "iio dev alloc failed.\n");
> +		return -ENOMEM;
> +	}
> +
> +	data = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	data->client = client;
> +	indio_dev->name = id->name;
> +	indio_dev->dev.of_node = client->dev.of_node;
> +	indio_dev->dev.parent = &client->dev;
> +
> +	if (!client->dev.of_node) {
> +		dev_err(&client->dev,
> +				"Not found DT.\n");
> +		return -EPERM;

Slightly odd error.  -ENODEV probably makes more sense...

> +	}
> +
> +	data->vcc_reg = devm_regulator_get(&client->dev, "vcc");
> +	if (IS_ERR(data->vcc_reg)) {
> +		ret = PTR_ERR(data->vcc_reg);
> +		dev_err(&client->dev,
> +			"Failed to get vcc-supply regulator: %d\n", ret);
> +		return ret;

return PTR_ERR(data->vcc_reg);

> +	}
> +
> +	mutex_init(&data->lock);
> +	ret = regulator_enable(data->vcc_reg);
> +	if (ret < 0) {
> +		dev_err(&client->dev,
> +				"Unable to enable the regulator.\n");
> +		return ret;
> +	}
> +
> +	usleep_range(1000, 1200);
> +	ret = ds4424_verify_chip(indio_dev);
> +	if (ret < 0)

regulator disable?  Easier if you do a goto block at the end
for any error handling which is not a valid direct return
(see below).

> +		return -ENXIO;
> +
> +	switch (id->driver_data) {
> +	case ID_DS4422:
> +		indio_dev->num_channels = DS4422_MAX_DAC_CHANNELS;
> +		break;
> +	case ID_DS4424:
> +		indio_dev->num_channels = DS4424_MAX_DAC_CHANNELS;
> +		break;
> +	default:
> +		dev_err(&client->dev,
> +				"ds4424: Invalid chip id.\n");
> +		regulator_disable(data->vcc_reg);

Given you have multiple error paths where regulator_disable is needed,
I would prefer this done as a goto with the error handling laid
out at the end of this function rather than mutiple copies inline.

> +		return -ENXIO;
> +	}
> +
> +	indio_dev->channels = ds4424_channels;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &ds4424_info;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret < 0) {
> +		dev_err(&client->dev,
> +				"iio_device_register failed. ret: %d\n", ret);
> +		regulator_disable(data->vcc_reg);
> +	}
> +
> +	return ret;
> +}
> +
> +static int ds4424_remove(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct ds4424_data *data = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +	regulator_disable(data->vcc_reg);
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id ds4424_id[] = {
> +	{ "ds4422", ID_DS4422 },
> +	{ "ds4424", ID_DS4424 },
> +	{ }
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, ds4424_id);
> +
> +static const struct of_device_id ds4424_of_match[] = {
> +	{ .compatible = "maxim,ds4422" },
> +	{ .compatible = "maxim,ds4424" },
> +	{ },
> +};
> +
> +MODULE_DEVICE_TABLE(of, ds4424_of_match);
> +
> +static struct i2c_driver ds4424_driver = {
> +	.driver = {
> +		.name	= "ds4424",
> +		.of_match_table = ds4424_of_match,
> +		.pm     = &ds4424_pm_ops,
> +	},
> +	.probe		= ds4424_probe,
> +	.remove		= ds4424_remove,
> +	.id_table	= ds4424_id,
> +};
> +module_i2c_driver(ds4424_driver);
> +
> +MODULE_DESCRIPTION("Maxim DS4424 DAC Driver");
> +MODULE_AUTHOR("Ismail H. Kose <ismail.kose@...imintegrated.com>");
> +MODULE_AUTHOR("Vishal Sood <vishal.sood@...imintegrated.com>");
> +MODULE_AUTHOR("David Jung <david.jung@...imintegrated.com>");
> +MODULE_LICENSE("GPL v2");

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