[PATCH v3] iio: dac: add support for max5522

[Angelo Dureghello <angelo.dureghello@timesys.com>]

Add initial support for DAC max5522.

Tested writing DAC A and B with some values,
from 0 to 1023, measured output voltages, driver works properly.

Additions for max5523/24/25 will follow.

Signed-off-by: Angelo Dureghello <angelo.dureghello@timesys.com>

---
Changes for v.2
- fix commit message
- Kconfig, fix depends and select
- Kconfig, fix typo
- fix include alphabetical order
- remove sysfs includes
- fix MAX5522_REG_DATA macro
- use devm_ as much as possible
- add regulator_enable
- remove useless code
- remove commas after structure initializers and null terminators
- change to use simplier module_spi_driver
- get id->name from device info structure
- regulator voltage read always from read_raw (no cache)

Changes for v.3
- move signed-off to be before the changelog
- re-fix include alphabetical order
- remove vrefin_mv references
- align function params with opening bracket
- try to get chip_info from firmware
- name always read from max5522_chip_info_tbl
- remove line break before MODULE_DEVICE_TABLE
---
 drivers/iio/dac/Kconfig   |  13 +++
 drivers/iio/dac/Makefile  |   1 +
 drivers/iio/dac/max5522.c | 207 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 221 insertions(+)
 create mode 100644 drivers/iio/dac/max5522.c

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 80521bd28d0f..6c49523fe357 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -357,6 +357,19 @@ config MAX517
 	  This driver can also be built as a module.  If so, the module
 	  will be called max517.
 
+config MAX5522
+	tristate "Maxim MAX5522 DAC driver"
+	depends on SPI_MASTER
+	select REGMAP_SPI
+	help
+	  Say Y here if you want to build a driver for the Maxim MAX5522.
+
+	  MAX5522 is a dual, ultra-low-power, 10-Bit, voltage-output
+	  digital to analog converter (DAC) offering rail-to-rail buffered
+	  voltage outputs.
+
+	  If compiled as a module, it will be called max5522.
+
 config MAX5821
 	tristate "Maxim MAX5821 DAC driver"
 	depends on I2C
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index ec3e42713f00..6c74fea21736 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -38,6 +38,7 @@ obj-$(CONFIG_LTC2632) += ltc2632.o
 obj-$(CONFIG_LTC2688) += ltc2688.o
 obj-$(CONFIG_M62332) += m62332.o
 obj-$(CONFIG_MAX517) += max517.o
+obj-$(CONFIG_MAX5522) += max5522.o
 obj-$(CONFIG_MAX5821) += max5821.o
 obj-$(CONFIG_MCP4725) += mcp4725.o
 obj-$(CONFIG_MCP4922) += mcp4922.o
diff --git a/drivers/iio/dac/max5522.c b/drivers/iio/dac/max5522.c
new file mode 100644
index 000000000000..00ba4e98fb9c
--- /dev/null
+++ b/drivers/iio/dac/max5522.c
@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Maxim MAX5522
+ * Dual, Ultra-Low-Power 10-Bit, Voltage-Output DACs
+ *
+ * Copyright 2022 Timesys Corp.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+#include <linux/spi/spi.h>
+
+#include <linux/iio/iio.h>
+
+#define MAX5522_MAX_ADDR	15
+#define MAX5522_CTRL_NONE	0
+#define MAX5522_CTRL_LOAD_IN_A	9
+#define MAX5522_CTRL_LOAD_IN_B	10
+
+#define MAX5522_REG_DATA(x)	((x) + MAX5522_CTRL_LOAD_IN_A)
+
+struct max5522_chip_info {
+	const char *name;
+	const struct iio_chan_spec *channels;
+	unsigned int num_channels;
+};
+
+struct max5522_state {
+	struct regmap *regmap;
+	const struct max5522_chip_info *chip_info;
+	unsigned short dac_cache[2];
+	struct regulator *vrefin_reg;
+};
+
+#define MAX5522_CHANNEL(chan) {	\
+	.type = IIO_VOLTAGE, \
+	.indexed = 1, \
+	.output = 1, \
+	.channel = chan, \
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
+			      BIT(IIO_CHAN_INFO_SCALE), \
+	.scan_type = { \
+		.sign = 'u', \
+		.realbits = 10, \
+		.storagebits = 16, \
+		.shift = 2, \
+	} \
+}
+
+const struct iio_chan_spec max5522_channels[] = {
+	MAX5522_CHANNEL(0),
+	MAX5522_CHANNEL(1),
+};
+
+enum max5522_type {
+	ID_MAX5522,
+};
+
+static const struct max5522_chip_info max5522_chip_info_tbl[] = {
+	[ID_MAX5522] = {
+		.name = "max5522",
+		.channels = max5522_channels,
+		.num_channels = 2,
+	},
+};
+
+static inline int max5522_info_to_reg(struct iio_chan_spec const *chan)
+{
+	return MAX5522_REG_DATA(chan->channel);
+}
+
+static int max5522_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long info)
+{
+	struct max5522_state *state = iio_priv(indio_dev);
+	int ret;
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		*val = state->dac_cache[chan->channel];
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		ret = regulator_get_voltage(state->vrefin_reg);
+		if (ret < 0)
+			return -EINVAL;
+		*val = ret / 1000;
+		*val2 = 10;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	default:
+		return -EINVAL;
+	}
+
+	return -EINVAL;
+}
+
+static int max5522_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long info)
+{
+	struct max5522_state *state = iio_priv(indio_dev);
+	int rval;
+
+	if (val > 1023 || val < 0)
+		return -EINVAL;
+
+	rval = regmap_write(state->regmap, max5522_info_to_reg(chan),
+			    val << chan->scan_type.shift);
+	if (rval < 0)
+		return rval;
+
+	state->dac_cache[chan->channel] = val;
+
+	return 0;
+}
+
+static const struct iio_info max5522_info = {
+	.read_raw = max5522_read_raw,
+	.write_raw = max5522_write_raw,
+};
+
+static const struct regmap_config max5522_regmap_config = {
+	.reg_bits = 4,
+	.val_bits = 12,
+	.max_register = MAX5522_MAX_ADDR,
+};
+
+static int max5522_spi_probe(struct spi_device *spi)
+{
+	const struct spi_device_id *id = spi_get_device_id(spi);
+	struct iio_dev *indio_dev;
+	struct max5522_state *state;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
+	if (indio_dev == NULL) {
+		dev_err(&spi->dev, "failed to allocate iio device\n");
+		return  -ENOMEM;
+	}
+
+	state = iio_priv(indio_dev);
+	state->chip_info = device_get_match_data(&spi->dev);
+	if (!state->chip_info) {
+		state->chip_info =
+			(struct max5522_chip_info *)(id->driver_data);
+		if (!state->chip_info)
+			return -EINVAL;
+	}
+
+	state->vrefin_reg = devm_regulator_get(&spi->dev, "vrefin");
+	if (IS_ERR(state->vrefin_reg))
+		return dev_err_probe(&spi->dev, PTR_ERR(state->vrefin_reg),
+				     "Vrefin regulator not specified\n");
+
+	ret = regulator_enable(state->vrefin_reg);
+	if (ret) {
+		return dev_err_probe(&spi->dev, ret,
+				     "Failed to enable vref regulators\n");
+	}
+
+	state->regmap = devm_regmap_init_spi(spi, &max5522_regmap_config);
+
+	if (IS_ERR(state->regmap))
+		return PTR_ERR(state->regmap);
+
+	indio_dev->info = &max5522_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = max5522_channels;
+	indio_dev->num_channels = ARRAY_SIZE(max5522_channels);
+	indio_dev->name = max5522_chip_info_tbl[ID_MAX5522].name;
+
+	return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct spi_device_id max5522_ids[] = {
+	{ "max5522", (kernel_ulong_t)&max5522_chip_info_tbl[ID_MAX5522] },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, max5522_ids);
+
+static const struct of_device_id max5522_of_match[] = {
+	{
+		.compatible = "maxim,max5522",
+		.data = &max5522_chip_info_tbl[ID_MAX5522],
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, max5522_of_match);
+
+static struct spi_driver max5522_spi_driver = {
+	.driver = {
+		.name = "max5522",
+		.of_match_table = max5522_of_match,
+	},
+	.probe = max5522_spi_probe,
+	.id_table = max5522_ids,
+};
+module_spi_driver(max5522_spi_driver);
+
+MODULE_AUTHOR("Angelo Dureghello <angelo.dureghello@timesys.com");
+MODULE_DESCRIPTION("MAX5522 DAC driver");
+MODULE_LICENSE("GPL");
-- 
2.38.1