Re: [PATCH] iio:dac: Add support for the AD7303

[Jonathan Cameron <jic23@kernel.org>]

On 06/11/2013 05:56 PM, Lars-Peter Clausen wrote:
> This patch adds support for the AD7303. The AD7303 is a simple 2 channel 8 bit
> DAC with an SPI interface.
> 

Do we need an explicit, 'Use the reference regulator' element in device tree
/platform data?  (I know this is done in existing drivers) Or would a simple
lack of having one specified be sufficient?  Are there real cases where
a board is designed with one, but we want to not use it (other than bugs
of course ;)  Doesn't seem to be documented.

Otherwise, whether you put a blank line before return statements is a bit
random in this driver.

Rest is fine and I'm only bring the above up because its that sort of an evening ;)
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> ---
>  .../devicetree/bindings/iio/dac/ad7303.txt         |  23 ++
>  drivers/iio/dac/Kconfig                            |  10 +
>  drivers/iio/dac/Makefile                           |   1 +
>  drivers/iio/dac/ad7303.c                           | 315 +++++++++++++++++++++
>  include/linux/platform_data/ad7303.h               |  21 ++
>  5 files changed, 370 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/dac/ad7303.txt
>  create mode 100644 drivers/iio/dac/ad7303.c
>  create mode 100644 include/linux/platform_data/ad7303.h
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/ad7303.txt b/Documentation/devicetree/bindings/iio/dac/ad7303.txt
> new file mode 100644
> index 0000000..914610f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/dac/ad7303.txt
> @@ -0,0 +1,23 @@
> +Analog Devices AD7303 DAC device driver
> +
> +Required properties:
> +	- compatible: Must be "adi,ad7303"
> +	- reg: SPI chip select number for the device
> +	- spi-max-frequency: Max SPI frequency to use (< 30000000)
> +	- Vdd-supply: Phandle to the Vdd power supply
> +
> +Optional properties:
> +	- REF-supply: Phandle to the external reference voltage supply. This should
> +	  only be set if there is an external reference voltage connected to the REF
> +	  pin. If the property is not set Vdd/2 is used as the reference voltage.
> +
> +Example:
> +
> +		ad7303@4 {
> +			compatible = "adi,ad7303";
> +			reg = <4>;
> +			spi-max-frequency = <10000000>;
> +			Vdd-supply = <&vdd_supply>;
> +			adi,use-external-reference;
above is a I think undocumented?

> +			REF-supply = <&vref_supply>;
> +		};
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index b61160b..c9c33ce 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -130,6 +130,16 @@ config AD5686
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ad5686.
>  
> +config AD7303
> +	tristate "Analog Devices Analog Devices AD7303 DAC driver"
> +	depends on SPI
> +	help
> +	  Say yes here to build support for Analog Devices AD7303 Digital to Analog
> +	  Converters (DAC).
> +
> +	  To compile this driver as module choose M here: the module will be called
> +	  ad7303.
> +
>  config MAX517
>  	tristate "Maxim MAX517/518/519 DAC driver"
>  	depends on I2C
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index 5b528eb..c8d7ab6 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -14,5 +14,6 @@ obj-$(CONFIG_AD5755) += ad5755.o
>  obj-$(CONFIG_AD5764) += ad5764.o
>  obj-$(CONFIG_AD5791) += ad5791.o
>  obj-$(CONFIG_AD5686) += ad5686.o
> +obj-$(CONFIG_AD7303) += ad7303.o
>  obj-$(CONFIG_MAX517) += max517.o
>  obj-$(CONFIG_MCP4725) += mcp4725.o
> diff --git a/drivers/iio/dac/ad7303.c b/drivers/iio/dac/ad7303.c
> new file mode 100644
> index 0000000..85aeef6
> --- /dev/null
> +++ b/drivers/iio/dac/ad7303.c
> @@ -0,0 +1,315 @@
> +/*
> + * AD7303 Digital to analog converters driver
> + *
> + * Copyright 2013 Analog Devices Inc.
> + *
> + * Licensed under the GPL-2.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/spi/spi.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/of.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +#include <linux/platform_data/ad7303.h>
> +
> +#define AD7303_CFG_EXTERNAL_VREF BIT(15)
> +#define AD7303_CFG_POWER_DOWN(ch) BIT(11 + (ch))
> +#define AD7303_CFG_ADDR_OFFSET	10
> +
> +#define AD7303_CMD_UPDATE_DAC	(0x3 << 8)
> +
> +/**
> + * struct ad7303_state - driver instance specific data
> + * @spi:		the device for this driver instance
> + * @config:		cached config register value
> + * @dac_cache:		current DAC raw value (chip does not support readback)
> + * @data:		spi transfer buffer
> + */
> +
> +struct ad7303_state {
> +	struct spi_device *spi;
> +	uint16_t config;
> +	uint8_t dac_cache[2];
> +
> +	struct regulator *vdd_reg;
> +	struct regulator *vref_reg;
> +
> +	/*
> +	 * DMA (thus cache coherency maintenance) requires the
> +	 * transfer buffers to live in their own cache lines.
> +	 */
> +	__be16 data ____cacheline_aligned;
> +};
> +
> +static int ad7303_write(struct ad7303_state *st, unsigned int chan,
> +	uint8_t val)
> +{
> +	st->data = cpu_to_be16(AD7303_CMD_UPDATE_DAC |
> +		(chan << AD7303_CFG_ADDR_OFFSET) |
> +		st->config | val);
> +
> +	return spi_write(st->spi, &st->data, sizeof(st->data));
> +}
> +
> +static ssize_t ad7303_read_dac_powerdown(struct iio_dev *indio_dev,
> +	uintptr_t private, const struct iio_chan_spec *chan, char *buf)
> +{
> +	struct ad7303_state *st = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%d\n", (bool)(st->config &
> +		AD7303_CFG_POWER_DOWN(chan->channel)));
> +}
> +
> +static ssize_t ad7303_write_dac_powerdown(struct iio_dev *indio_dev,
> +	 uintptr_t private, const struct iio_chan_spec *chan, const char *buf,
> +	 size_t len)
> +{
> +	struct ad7303_state *st = iio_priv(indio_dev);
> +	bool pwr_down;
> +	int ret;
> +
> +	ret = strtobool(buf, &pwr_down);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&indio_dev->mlock);
> +
> +	if (pwr_down)
> +		st->config |= AD7303_CFG_POWER_DOWN(chan->channel);
> +	else
> +		st->config &= ~AD7303_CFG_POWER_DOWN(chan->channel);
> +
> +	/* There is no noop cmd which allows us to only update the powerdown
> +	 * mode, so just write one of the DAC channels again */
> +	ad7303_write(st, chan->channel, st->dac_cache[chan->channel]);
> +
> +	mutex_unlock(&indio_dev->mlock);
> +	return ret ? ret : len;
> +}
> +
> +static int ad7303_get_vref(struct ad7303_state *st,
> +	struct iio_chan_spec const *chan)
> +{
> +	int ret;
> +
> +	if (st->config & AD7303_CFG_EXTERNAL_VREF)
> +		return regulator_get_voltage(st->vref_reg);
> +
> +	ret = regulator_get_voltage(st->vdd_reg);
> +	if (ret < 0)
> +		return ret;
> +	return ret / 2;
> +}
> +
> +static int ad7303_read_raw(struct iio_dev *indio_dev,
> +	struct iio_chan_spec const *chan, int *val, int *val2, long info)
> +{
> +	struct ad7303_state *st = iio_priv(indio_dev);
> +	int vref_uv;
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW:
> +		*val = st->dac_cache[chan->channel];
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		vref_uv = ad7303_get_vref(st, chan);
> +		if (vref_uv < 0)
> +			return vref_uv;
> +
> +		*val = 2 * vref_uv / 1000;
> +		*val2 = chan->scan_type.realbits;
> +
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	default:
> +		break;
> +	}
> +	return -EINVAL;
> +}
> +
> +static int ad7303_write_raw(struct iio_dev *indio_dev,
> +	struct iio_chan_spec const *chan, int val, int val2, long mask)
> +{
> +	struct ad7303_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (val >= (1 << chan->scan_type.realbits) || val < 0)
> +			return -EINVAL;
> +
> +		mutex_lock(&indio_dev->mlock);
> +		ret = ad7303_write(st, chan->address, val);
> +		if (ret == 0)
> +			st->dac_cache[chan->channel] = val;
> +		mutex_unlock(&indio_dev->mlock);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +
> +	return ret;
> +}
> +
> +static const struct iio_info ad7303_info = {
> +	.read_raw = ad7303_read_raw,
> +	.write_raw = ad7303_write_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static const struct iio_chan_spec_ext_info ad7303_ext_info[] = {
> +	{
> +		.name = "powerdown",
> +		.read = ad7303_read_dac_powerdown,
> +		.write = ad7303_write_dac_powerdown,
> +	},
> +	{ },
> +};
> +
> +#define AD7303_CHANNEL(chan) {					\
> +	.type = IIO_VOLTAGE,					\
> +	.indexed = 1,						\
> +	.output = 1,						\
> +	.channel = (chan),					\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +	.address = (chan),					\
> +	.scan_type = {						\
> +		.sign = 'u',					\
> +		.realbits = '8',				\
> +		.storagebits = '8',				\
> +		.shift = '0',					\
> +	},							\
> +	.ext_info = ad7303_ext_info,				\
> +}
> +
> +static const struct iio_chan_spec ad7303_channels[] = {
> +	AD7303_CHANNEL(0),
> +	AD7303_CHANNEL(1),
> +};
> +
> +static int ad7303_probe(struct spi_device *spi)
> +{
> +	const struct spi_device_id *id = spi_get_device_id(spi);
> +	struct iio_dev *indio_dev;
> +	struct ad7303_state *st;
> +	bool ext_ref;
> +	int ret;
> +
> +	indio_dev = iio_device_alloc(sizeof(*st));
> +	if (indio_dev == NULL)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	st->spi = spi;
> +
> +	st->vdd_reg = regulator_get(&spi->dev, "Vdd");
> +	if (IS_ERR(st->vdd_reg)) {
> +		ret = PTR_ERR(st->vdd_reg);
> +		goto err_free;
> +	}
> +
> +	ret = regulator_enable(st->vdd_reg);
> +	if (ret)
> +		goto err_put_vdd_reg;
> +
> +	if (spi->dev.of_node) {
> +		ext_ref = of_property_read_bool(spi->dev.of_node,
> +				"REF-supply");
> +	} else {
> +		struct ad7303_platform_data *pdata = spi->dev.platform_data;
> +		if (pdata && pdata->use_external_ref)
> +			ext_ref = true;
> +		else
> +		    ext_ref = false;
> +	}
> +
> +	if (ext_ref) {
> +		st->vref_reg = regulator_get(&spi->dev, "REF");
> +		if (IS_ERR(st->vref_reg))
> +			goto err_disable_vdd_reg;
> +
> +		ret = regulator_enable(st->vref_reg);
> +		if (ret)
> +			goto err_put_vref_reg;
> +
> +		st->config |= AD7303_CFG_EXTERNAL_VREF;
> +	}
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->name = id->name;
> +	indio_dev->info = &ad7303_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = ad7303_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(ad7303_channels);
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret)
> +		goto err_disable_vref_reg;
> +
> +	return 0;
> +
> +err_disable_vref_reg:
> +	if (st->vref_reg)
> +		regulator_disable(st->vref_reg);
> +err_put_vref_reg:
> +	if (st->vref_reg)
> +		regulator_put(st->vref_reg);
> +err_disable_vdd_reg:
> +	regulator_disable(st->vdd_reg);
> +err_put_vdd_reg:
> +	regulator_put(st->vdd_reg);
> +err_free:
> +	iio_device_free(indio_dev);
> +
> +	return ret;
> +}
> +
> +static int ad7303_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct ad7303_state *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	if (st->vref_reg) {
> +		regulator_disable(st->vref_reg);
> +		regulator_put(st->vref_reg);
> +	}
> +	regulator_disable(st->vdd_reg);
> +	regulator_put(st->vdd_reg);
> +
> +	iio_device_free(indio_dev);
> +
> +	return 0;
> +}
> +
> +static const struct spi_device_id ad7303_spi_ids[] = {
> +	{ "ad7303", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, ad7303_spi_ids);
> +
> +static struct spi_driver ad7303_driver = {
> +	.driver = {
> +		.name = "ad7303",
> +		.owner = THIS_MODULE,
> +	},
> +	.probe = ad7303_probe,
> +	.remove = ad7303_remove,
> +	.id_table = ad7303_spi_ids,
> +};
> +module_spi_driver(ad7303_driver);
> +
> +MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
> +MODULE_DESCRIPTION("Analog Devices AD7303 DAC driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/platform_data/ad7303.h b/include/linux/platform_data/ad7303.h
> new file mode 100644
> index 0000000..de6a7a6
> --- /dev/null
> +++ b/include/linux/platform_data/ad7303.h
> @@ -0,0 +1,21 @@
> +/*
> + * Analog Devices AD7303 DAC driver
> + *
> + * Copyright 2013 Analog Devices Inc.
> + *
> + * Licensed under the GPL-2.
> + */
> +
> +#ifndef __IIO_ADC_AD7303_H__
> +#define __IIO_ADC_AD7303_H__
> +
> +/**
> + * struct ad7303_platform_data - AD7303 platform data
> + * @use_external_ref: If set to true use an external voltage reference connected
> + * to the REF pin, otherwise use the internal reference derived from Vdd.
> + */
> +struct ad7303_platform_data {
> +	bool use_external_ref;
> +};
> +
> +#endif
>