iio:dac: Add support for the AD7303

This patch adds support for the AD7303. The AD7303 is a simple 2 channel 8 bit
DAC with an SPI interface.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

3 files changed, 326 insertions, 0 deletions

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index b61160bd935e..c9c33ce32d3a 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 5b528ebb3343..c8d7ab6bff01 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 000000000000..85aeef60dc5f
--- /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");