iio:dac:ti-dac7612: Add driver for Texas Instruments DAC7612

It is a driver for Texas Instruments Dual, 12-Bit Serial Input
Digital-to-Analog Converter.

Datasheet of this chip:
http://www.ti.com/lit/ds/sbas106/sbas106.pdfSigned-off-by: Ricardo Ribalda Delgado <ricardo@ribalda.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

MAINTAINERS

@@ -15082,6 +15082,12 @@ L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
 S:	Maintained
 F:	sound/soc/ti/
 
+Texas Instruments' DAC7612 DAC Driver
+M:	Ricardo Ribalda <ricardo@ribalda.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+F:	drivers/iio/dac/ti-dac7612.c
+
 THANKO'S RAREMONO AM/FM/SW RADIO RECEIVER USB DRIVER
 M:	Hans Verkuil <hverkuil@xs4all.nl>
 L:	linux-media@vger.kernel.org

drivers/iio/dac/Kconfig

@@ -375,6 +375,16 @@ config TI_DAC7311
 
 	  If compiled as a module, it will be called ti-dac7311.
 
+config TI_DAC7612
+	tristate "Texas Instruments 12-bit 2-channel DAC driver"
+	depends on SPI_MASTER && GPIOLIB
+	help
+	  Driver for the Texas Instruments DAC7612, DAC7612U, DAC7612UB
+	  The driver hand drive the load pin automatically, otherwise
+	  it needs to be toggled manually.
+
+	  If compiled as a module, it will be called ti-dac7612.
+
 config VF610_DAC
 	tristate "Vybrid vf610 DAC driver"
 	depends on OF

drivers/iio/dac/Makefile

@@ -41,4 +41,5 @@ obj-$(CONFIG_STM32_DAC) += stm32-dac.o
 obj-$(CONFIG_TI_DAC082S085) += ti-dac082s085.o
 obj-$(CONFIG_TI_DAC5571) += ti-dac5571.o
 obj-$(CONFIG_TI_DAC7311) += ti-dac7311.o
+obj-$(CONFIG_TI_DAC7612) += ti-dac7612.o
 obj-$(CONFIG_VF610_DAC) += vf610_dac.o

drivers/iio/dac/ti-dac7612.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DAC7612 Dual, 12-Bit Serial input Digital-to-Analog Converter
+ *
+ * Copyright 2019 Qtechnology A/S
+ * 2019 Ricardo Ribalda <ricardo@ribalda.com>
+ *
+ * Licensed under the GPL-2.
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+
+#define DAC7612_RESOLUTION 12
+#define DAC7612_ADDRESS 4
+#define DAC7612_START 5
+
+struct dac7612 {
+	struct spi_device *spi;
+	struct gpio_desc *loaddacs;
+	uint16_t cache[2];
+
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	uint8_t data[2] ____cacheline_aligned;
+};
+
+static int dac7612_cmd_single(struct dac7612 *priv, int channel, u16 val)
+{
+	int ret;
+
+	priv->data[0] = BIT(DAC7612_START) | (channel << DAC7612_ADDRESS);
+	priv->data[0] |= val >> 8;
+	priv->data[1] = val & 0xff;
+
+	priv->cache[channel] = val;
+
+	ret = spi_write(priv->spi, priv->data, sizeof(priv->data));
+	if (ret)
+		return ret;
+
+	gpiod_set_value(priv->loaddacs, 1);
+	gpiod_set_value(priv->loaddacs, 0);
+
+	return 0;
+}
+
+#define dac7612_CHANNEL(chan, name) {				\
+	.type = IIO_VOLTAGE,					\
+	.channel = (chan),					\
+	.indexed = 1,						\
+	.output = 1,						\
+	.datasheet_name = name,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+}
+
+static const struct iio_chan_spec dac7612_channels[] = {
+	dac7612_CHANNEL(0, "OUTA"),
+	dac7612_CHANNEL(1, "OUTB"),
+};
+
+static int dac7612_read_raw(struct iio_dev *iio_dev,
+			    const struct iio_chan_spec *chan,
+			    int *val, int *val2, long mask)
+{
+	struct dac7612 *priv;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		priv = iio_priv(iio_dev);
+		*val = priv->cache[chan->channel];
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		*val = 1;
+		return IIO_VAL_INT;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int dac7612_write_raw(struct iio_dev *iio_dev,
+			     const struct iio_chan_spec *chan,
+			     int val, int val2, long mask)
+{
+	struct dac7612 *priv = iio_priv(iio_dev);
+	int ret;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	if ((val >= BIT(DAC7612_RESOLUTION)) || val < 0 || val2)
+		return -EINVAL;
+
+	if (val == priv->cache[chan->channel])
+		return 0;
+
+	mutex_lock(&iio_dev->mlock);
+	ret = dac7612_cmd_single(priv, chan->channel, val);
+	mutex_unlock(&iio_dev->mlock);
+
+	return ret;
+}
+
+static const struct iio_info dac7612_info = {
+	.read_raw = dac7612_read_raw,
+	.write_raw = dac7612_write_raw,
+};
+
+static int dac7612_probe(struct spi_device *spi)
+{
+	struct iio_dev *iio_dev;
+	struct dac7612 *priv;
+	int i;
+	int ret;
+
+	iio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*priv));
+	if (!iio_dev)
+		return -ENOMEM;
+
+	priv = iio_priv(iio_dev);
+	/*
+	 * LOADDACS pin can be controlled by the driver or externally.
+	 * When controlled by the driver, the DAC value is updated after
+	 * every write.
+	 * When the driver does not control the PIN, the user or an external
+	 * event can change the value of all DACs by pulsing down the LOADDACs
+	 * pin.
+	 */
+	priv->loaddacs = devm_gpiod_get_optional(&spi->dev, "ti,loaddacs",
+						 GPIOD_OUT_LOW);
+	if (IS_ERR(priv->loaddacs))
+		return PTR_ERR(priv->loaddacs);
+	priv->spi = spi;
+	spi_set_drvdata(spi, iio_dev);
+	iio_dev->dev.parent = &spi->dev;
+	iio_dev->info = &dac7612_info;
+	iio_dev->modes = INDIO_DIRECT_MODE;
+	iio_dev->channels = dac7612_channels;
+	iio_dev->num_channels = ARRAY_SIZE(priv->cache);
+	iio_dev->name = spi_get_device_id(spi)->name;
+
+	for (i = 0; i < ARRAY_SIZE(priv->cache); i++) {
+		ret = dac7612_cmd_single(priv, i, 0);
+		if (ret)
+			return ret;
+	}
+
+	return devm_iio_device_register(&spi->dev, iio_dev);
+}
+
+static const struct spi_device_id dac7612_id[] = {
+	{"ti-dac7612"},
+	{}
+};
+MODULE_DEVICE_TABLE(spi, dac7612_id);
+
+static const struct of_device_id dac7612_of_match[] = {
+	{ .compatible = "ti,dac7612" },
+	{ .compatible = "ti,dac7612u" },
+	{ .compatible = "ti,dac7612ub" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, dac7612_of_match);
+
+static struct spi_driver dac7612_driver = {
+	.driver = {
+		   .name = "ti-dac7612",
+		   .of_match_table = dac7612_of_match,
+		   },
+	.probe = dac7612_probe,
+	.id_table = dac7612_id,
+};
+module_spi_driver(dac7612_driver);
+
+MODULE_AUTHOR("Ricardo Ribalda <ricardo@ribalda.com>");
+MODULE_DESCRIPTION("Texas Instruments DAC7612 DAC driver");
+MODULE_LICENSE("GPL v2");