[PATCH 1/2] iio: document ti-dac8554 devicetree bindings

[PATCH 1/2] iio: document ti-dac8554 devicetree bindings

[Nikolaus Schulz]

Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
---
 .../devicetree/bindings/iio/dac/ti-dac8554.txt     | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt

diff --git a/Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt b/Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt
new file mode 100644
index 0000000..16f7178
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt
@@ -0,0 +1,22 @@
+TI DAC8554 Digital to Analog Converter
+
+This driver supports the SPI bus.
+
+Required properties:
+	- compatible: must be "ti,dac8554"
+	- vref-supply: the vref power supply
+	- address: the additional 2-bit chip address
+
+For required properties on SPI, please consult
+Documentation/devicetree/bindings/spi/spi-bus.txt
+
+Example:
+
+	dac8554@0 {
+		compatible = "ti,dac8554";
+		reg = <0>;
+		spi-max-frequency = <50000000>;
+
+		vref-supply = <&vdd_vref>;
+		address = <0>;
+	};
-- 
2.1.3

[PATCH 1/2] iio: document ti-dac8554 devicetree bindings

[Nikolaus Schulz]

Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
---
 .../devicetree/bindings/iio/dac/ti-dac8554.txt     | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt

diff --git a/Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt b/Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt
new file mode 100644
index 0000000..16f7178
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/dac/ti-dac8554.txt
@@ -0,0 +1,22 @@
+TI DAC8554 Digital to Analog Converter
+
+This driver supports the SPI bus.
+
+Required properties:
+	- compatible: must be "ti,dac8554"
+	- vref-supply: the vref power supply
+	- address: the additional 2-bit chip address
+
+For required properties on SPI, please consult
+Documentation/devicetree/bindings/spi/spi-bus.txt
+
+Example:
+
+	dac8554@0 {
+		compatible = "ti,dac8554";
+		reg = <0>;
+		spi-max-frequency = <50000000>;
+
+		vref-supply = <&vdd_vref>;
+		address = <0>;
+	};
-- 
2.1.3

[PATCH 2/2] iio: add driver for the TI DAC8554

[Nikolaus Schulz]

The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
interface.

Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
---
 drivers/iio/dac/Kconfig      |  10 ++
 drivers/iio/dac/Makefile     |   1 +
 drivers/iio/dac/ti-dac8554.c | 365 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 376 insertions(+)
 create mode 100644 drivers/iio/dac/ti-dac8554.c

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 2236ea2..1689260 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -181,4 +181,14 @@ config MCP4922
 	  To compile this driver as a module, choose M here: the module
 	  will be called mcp4922.
 
+config TI_DAC8554
+	tristate "TI DAC8554 driver"
+	depends on SPI
+	depends on OF
+	help
+	  Say yes here to build the driver for the TI DAC8554.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called ti-dac8554.
+
 endmenu
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 52be7e1..b98d79a 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -20,3 +20,4 @@ obj-$(CONFIG_MAX517) += max517.o
 obj-$(CONFIG_MAX5821) += max5821.o
 obj-$(CONFIG_MCP4725) += mcp4725.o
 obj-$(CONFIG_MCP4922) += mcp4922.o
+obj-$(CONFIG_TI_DAC8554) += ti-dac8554.o
diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
new file mode 100644
index 0000000..9c135e1
--- /dev/null
+++ b/drivers/iio/dac/ti-dac8554.c
@@ -0,0 +1,365 @@
+/*
+ * TI DAC8554 Digital to Analog Converter SPI driver
+ *
+ * Copyright (C) 2014 Avionic Design GmbH
+ *
+ * Based on ad5446r_spi.c
+ * Copyright (C) 2010,2011 Analog Devices Inc.
+ *
+ * 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/spi/spi.h>
+#include <linux/regulator/consumer.h>
+#include <linux/module.h>
+#include <linux/iio/iio.h>
+#include <linux/of.h>
+
+#define DAC8554_DRIVERNAME			"ti-dac8554"
+#define DAC8554_DAC_CHANNELS			4
+
+/* Load commands */
+#define DAC8554_CMD_STORE_DAC_N			0x0
+#define DAC8554_CMD_UPDATE_DAC_N		0x1
+#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
+#define DAC8554_CMD_UPDATE_BROADCAST		0x3
+
+#define DAC8554_BROADCAST_USE_SRDATA		0x2
+/* Powerdown modes (ORed PD1|PD2 bits) */
+#define DAC8554_PWRDN_HIZ			0x0
+#define DAC8554_PWRDN_1K			0x1
+#define DAC8554_PWRDN_100K			0x2
+
+#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
+
+/**
+ * struct dac8554_state - driver instance specific data
+ * @spi:		spi_device
+ * @reg:		supply regulator
+ * @addr:		two-bit chip address
+ * @vref_mv:		reference voltage in millivolt
+ * @val			DAC/channel data
+ * @powerdown		channel powerdown flag
+ * @powerdown_mode	channel powerdown mode
+ */
+struct dac8554_state {
+	struct spi_device		*spi;
+	struct regulator		*reg;
+	unsigned			addr;
+	unsigned			vref_mv;
+	u16				val[DAC8554_DAC_CHANNELS];
+	bool				powerdown[DAC8554_DAC_CHANNELS];
+	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
+};
+
+static int dac8554_spi_write(struct spi_device *spi,
+			     unsigned chip_addr, unsigned cmd,
+			     unsigned chan_addr, unsigned val)
+{
+	u32 data;
+	u8 msg[3];
+
+	/*
+	 * The input shift register is 24 bits wide. The 8 MSB are
+	 * control bits, followed by 16 data bits.
+	 * The first two bits A1 and A0 address a DAC8554 chip.
+	 * The next two are the command bits, LD1 and LD0.
+	 * After a don't-care-bit, the next two bits select the channel.
+	 * The final control bit PD0 is a flag signalling if the data
+	 * bits encode a powerdown mode. We merge PD0 with the adjacent
+	 * data bits.
+	 */
+
+	if (chip_addr > 3 || cmd > 3 || chan_addr > 3 ||
+			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
+		return -EINVAL;
+
+	data = (chip_addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
+	msg[0] = data >> 16;
+	msg[1] = data >> 8;
+	msg[2] = data;
+
+	return spi_write(spi, msg, sizeof(msg));
+}
+
+static int dac8554_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val,
+			    int *val2,
+			    long m)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	switch (m) {
+	case IIO_CHAN_INFO_RAW:
+		*val = st->val[chan->address];
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = st->vref_mv;
+		*val2 = 16;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	}
+	return -EINVAL;
+}
+
+static int dac8554_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val,
+			     int val2,
+			     long mask)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+	int err = 0;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (val > 0xffff || val < 0)
+			return -EINVAL;
+
+		err = dac8554_spi_write(st->spi, st->addr,
+				DAC8554_CMD_UPDATE_DAC_N,
+				chan->address, val);
+		if (err)
+			return err;
+
+		st->val[chan->address] = val;
+
+		/* By hw design, DAC updates automatically trigger powerup. */
+		st->powerdown[chan->address] = false;
+
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	return st->powerdown_mode[chan->address];
+}
+
+static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan,
+				      unsigned int mode)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	st->powerdown_mode[chan->address] = mode;
+
+	return 0;
+}
+
+static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
+					  uintptr_t private,
+					  const struct iio_chan_spec *chan,
+					  char *buf)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
+}
+
+static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
+					   uintptr_t private,
+					   const struct iio_chan_spec *chan,
+					   const char *buf,
+					   size_t len)
+{
+	bool powerdown;
+	int ret;
+	struct dac8554_state *st = iio_priv(indio_dev);
+	u8 powerdown_mode;
+
+	ret = strtobool(buf, &powerdown);
+	if (ret)
+		return ret;
+
+	st->powerdown[chan->address] = powerdown;
+
+	if (powerdown) {
+		powerdown_mode = st->powerdown_mode[chan->address];
+		ret = dac8554_spi_write(st->spi, st->addr,
+				DAC8554_CMD_UPDATE_DAC_N,
+				chan->address,
+				DAC8554_PWRDN_TO_SR(powerdown_mode));
+	} else {
+		/* Load DAC with cached value. This triggers a powerup. */
+		ret = dac8554_spi_write(st->spi, st->addr,
+				DAC8554_CMD_UPDATE_DAC_N,
+				chan->address,
+				st->val[chan->address]);
+	}
+
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static int dac8554_powerdown_broadcast(struct dac8554_state *st,
+				       u8 powerdown_mode)
+{
+	int ret;
+
+	ret = dac8554_spi_write(st->spi, 0,
+			DAC8554_CMD_UPDATE_BROADCAST,
+			DAC8554_BROADCAST_USE_SRDATA,
+			DAC8554_PWRDN_TO_SR(powerdown_mode));
+	if (ret)
+		return ret;
+
+	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
+	memset(st->powerdown, true, sizeof(st->powerdown));
+
+	return 0;
+}
+
+static const struct iio_info dac8554_info = {
+	.write_raw = dac8554_write_raw,
+	.read_raw = dac8554_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static const char * const dac8554_powerdown_modes[] = {
+	"hi-z",
+	"1kohm_to_gnd",
+	"100kohm_to_gnd"
+};
+
+static const struct iio_enum dac8854_powerdown_mode_enum = {
+	.items = dac8554_powerdown_modes,
+	.num_items = ARRAY_SIZE(dac8554_powerdown_modes),
+	.get = dac8554_get_powerdown_mode,
+	.set = dac8554_set_powerdown_mode,
+};
+
+static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
+	{
+		.name = "powerdown",
+		.read = dac8554_read_dac_powerdown,
+		.write = dac8554_write_dac_powerdown,
+		.shared = IIO_SEPARATE,
+	},
+	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
+		 &dac8854_powerdown_mode_enum),
+	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
+	{ },
+};
+
+#define DAC8554_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), \
+	.ext_info = dac8554_ext_info, \
+}
+const struct iio_chan_spec dac8554_channels[] = {
+	DAC8554_CHANNEL(0),
+	DAC8554_CHANNEL(1),
+	DAC8554_CHANNEL(2),
+	DAC8554_CHANNEL(3),
+};
+#undef DAC8554_CHANNEL
+
+static int dac8554_probe(struct spi_device *spi)
+{
+	struct dac8554_state *st;
+	struct iio_dev *indio_dev;
+	int ret, voltage_uv = 0;
+	u32 addr;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->name = DAC8554_DRIVERNAME;
+	indio_dev->info = &dac8554_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = dac8554_channels;
+	indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
+
+	spi_set_drvdata(spi, indio_dev);
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		return ret;
+
+	st = iio_priv(indio_dev);
+
+	if (!spi->dev.of_node) {
+		dev_err(&spi->dev, "missing OF node");
+		return -ENODEV;
+	}
+	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
+	if (ret || addr > 2) {
+		dev_err(&spi->dev, "no or invalid chip address");
+		return -ENODEV;
+	}
+
+	st->spi = spi;
+	st->addr = addr;
+
+	st->reg = devm_regulator_get(&spi->dev, "vref");
+	if (IS_ERR(st->reg))
+		return PTR_ERR(st->reg);
+
+	ret = regulator_enable(st->reg);
+	if (ret)
+		return ret;
+
+	voltage_uv = regulator_get_voltage(st->reg);
+	if (voltage_uv < 0)
+		goto error_disable_reg;
+	st->vref_mv = voltage_uv / 1000;
+
+	ret = dac8554_powerdown_broadcast(st, DAC8554_PWRDN_100K);
+	if (ret)
+		goto error_disable_reg;
+
+	return 0;
+
+error_disable_reg:
+	regulator_disable(st->reg);
+	return ret;
+}
+
+static int dac8554_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	regulator_disable(st->reg);
+
+	return 0;
+}
+
+static const struct of_device_id dac8554_of_match[] = {
+	{ .compatible = "ti,dac8554" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dac8554_of_match);
+
+static struct spi_driver dac8554_driver = {
+	.driver = {
+		.name = DAC8554_DRIVERNAME,
+		.owner = THIS_MODULE,
+		.of_match_table = dac8554_of_match,
+	 },
+	.probe = dac8554_probe,
+	.remove = dac8554_remove,
+};
+module_spi_driver(dac8554_driver);
+
+MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz@avionic-design.de>");
+MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
+MODULE_LICENSE("GPL v2");
-- 
2.1.3

[PATCH 2/2] iio: add driver for the TI DAC8554

[Nikolaus Schulz]

The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
interface.

Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
---
 drivers/iio/dac/Kconfig      |  10 ++
 drivers/iio/dac/Makefile     |   1 +
 drivers/iio/dac/ti-dac8554.c | 365 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 376 insertions(+)
 create mode 100644 drivers/iio/dac/ti-dac8554.c

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 2236ea2..1689260 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -181,4 +181,14 @@ config MCP4922
 	  To compile this driver as a module, choose M here: the module
 	  will be called mcp4922.
 
+config TI_DAC8554
+	tristate "TI DAC8554 driver"
+	depends on SPI
+	depends on OF
+	help
+	  Say yes here to build the driver for the TI DAC8554.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called ti-dac8554.
+
 endmenu
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 52be7e1..b98d79a 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -20,3 +20,4 @@ obj-$(CONFIG_MAX517) += max517.o
 obj-$(CONFIG_MAX5821) += max5821.o
 obj-$(CONFIG_MCP4725) += mcp4725.o
 obj-$(CONFIG_MCP4922) += mcp4922.o
+obj-$(CONFIG_TI_DAC8554) += ti-dac8554.o
diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
new file mode 100644
index 0000000..9c135e1
--- /dev/null
+++ b/drivers/iio/dac/ti-dac8554.c
@@ -0,0 +1,365 @@
+/*
+ * TI DAC8554 Digital to Analog Converter SPI driver
+ *
+ * Copyright (C) 2014 Avionic Design GmbH
+ *
+ * Based on ad5446r_spi.c
+ * Copyright (C) 2010,2011 Analog Devices Inc.
+ *
+ * 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/spi/spi.h>
+#include <linux/regulator/consumer.h>
+#include <linux/module.h>
+#include <linux/iio/iio.h>
+#include <linux/of.h>
+
+#define DAC8554_DRIVERNAME			"ti-dac8554"
+#define DAC8554_DAC_CHANNELS			4
+
+/* Load commands */
+#define DAC8554_CMD_STORE_DAC_N			0x0
+#define DAC8554_CMD_UPDATE_DAC_N		0x1
+#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
+#define DAC8554_CMD_UPDATE_BROADCAST		0x3
+
+#define DAC8554_BROADCAST_USE_SRDATA		0x2
+/* Powerdown modes (ORed PD1|PD2 bits) */
+#define DAC8554_PWRDN_HIZ			0x0
+#define DAC8554_PWRDN_1K			0x1
+#define DAC8554_PWRDN_100K			0x2
+
+#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
+
+/**
+ * struct dac8554_state - driver instance specific data
+ * @spi:		spi_device
+ * @reg:		supply regulator
+ * @addr:		two-bit chip address
+ * @vref_mv:		reference voltage in millivolt
+ * @val			DAC/channel data
+ * @powerdown		channel powerdown flag
+ * @powerdown_mode	channel powerdown mode
+ */
+struct dac8554_state {
+	struct spi_device		*spi;
+	struct regulator		*reg;
+	unsigned			addr;
+	unsigned			vref_mv;
+	u16				val[DAC8554_DAC_CHANNELS];
+	bool				powerdown[DAC8554_DAC_CHANNELS];
+	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
+};
+
+static int dac8554_spi_write(struct spi_device *spi,
+			     unsigned chip_addr, unsigned cmd,
+			     unsigned chan_addr, unsigned val)
+{
+	u32 data;
+	u8 msg[3];
+
+	/*
+	 * The input shift register is 24 bits wide. The 8 MSB are
+	 * control bits, followed by 16 data bits.
+	 * The first two bits A1 and A0 address a DAC8554 chip.
+	 * The next two are the command bits, LD1 and LD0.
+	 * After a don't-care-bit, the next two bits select the channel.
+	 * The final control bit PD0 is a flag signalling if the data
+	 * bits encode a powerdown mode. We merge PD0 with the adjacent
+	 * data bits.
+	 */
+
+	if (chip_addr > 3 || cmd > 3 || chan_addr > 3 ||
+			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
+		return -EINVAL;
+
+	data = (chip_addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
+	msg[0] = data >> 16;
+	msg[1] = data >> 8;
+	msg[2] = data;
+
+	return spi_write(spi, msg, sizeof(msg));
+}
+
+static int dac8554_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val,
+			    int *val2,
+			    long m)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	switch (m) {
+	case IIO_CHAN_INFO_RAW:
+		*val = st->val[chan->address];
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = st->vref_mv;
+		*val2 = 16;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	}
+	return -EINVAL;
+}
+
+static int dac8554_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val,
+			     int val2,
+			     long mask)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+	int err = 0;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (val > 0xffff || val < 0)
+			return -EINVAL;
+
+		err = dac8554_spi_write(st->spi, st->addr,
+				DAC8554_CMD_UPDATE_DAC_N,
+				chan->address, val);
+		if (err)
+			return err;
+
+		st->val[chan->address] = val;
+
+		/* By hw design, DAC updates automatically trigger powerup. */
+		st->powerdown[chan->address] = false;
+
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	return st->powerdown_mode[chan->address];
+}
+
+static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan,
+				      unsigned int mode)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	st->powerdown_mode[chan->address] = mode;
+
+	return 0;
+}
+
+static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
+					  uintptr_t private,
+					  const struct iio_chan_spec *chan,
+					  char *buf)
+{
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
+}
+
+static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
+					   uintptr_t private,
+					   const struct iio_chan_spec *chan,
+					   const char *buf,
+					   size_t len)
+{
+	bool powerdown;
+	int ret;
+	struct dac8554_state *st = iio_priv(indio_dev);
+	u8 powerdown_mode;
+
+	ret = strtobool(buf, &powerdown);
+	if (ret)
+		return ret;
+
+	st->powerdown[chan->address] = powerdown;
+
+	if (powerdown) {
+		powerdown_mode = st->powerdown_mode[chan->address];
+		ret = dac8554_spi_write(st->spi, st->addr,
+				DAC8554_CMD_UPDATE_DAC_N,
+				chan->address,
+				DAC8554_PWRDN_TO_SR(powerdown_mode));
+	} else {
+		/* Load DAC with cached value. This triggers a powerup. */
+		ret = dac8554_spi_write(st->spi, st->addr,
+				DAC8554_CMD_UPDATE_DAC_N,
+				chan->address,
+				st->val[chan->address]);
+	}
+
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static int dac8554_powerdown_broadcast(struct dac8554_state *st,
+				       u8 powerdown_mode)
+{
+	int ret;
+
+	ret = dac8554_spi_write(st->spi, 0,
+			DAC8554_CMD_UPDATE_BROADCAST,
+			DAC8554_BROADCAST_USE_SRDATA,
+			DAC8554_PWRDN_TO_SR(powerdown_mode));
+	if (ret)
+		return ret;
+
+	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
+	memset(st->powerdown, true, sizeof(st->powerdown));
+
+	return 0;
+}
+
+static const struct iio_info dac8554_info = {
+	.write_raw = dac8554_write_raw,
+	.read_raw = dac8554_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static const char * const dac8554_powerdown_modes[] = {
+	"hi-z",
+	"1kohm_to_gnd",
+	"100kohm_to_gnd"
+};
+
+static const struct iio_enum dac8854_powerdown_mode_enum = {
+	.items = dac8554_powerdown_modes,
+	.num_items = ARRAY_SIZE(dac8554_powerdown_modes),
+	.get = dac8554_get_powerdown_mode,
+	.set = dac8554_set_powerdown_mode,
+};
+
+static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
+	{
+		.name = "powerdown",
+		.read = dac8554_read_dac_powerdown,
+		.write = dac8554_write_dac_powerdown,
+		.shared = IIO_SEPARATE,
+	},
+	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
+		 &dac8854_powerdown_mode_enum),
+	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
+	{ },
+};
+
+#define DAC8554_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), \
+	.ext_info = dac8554_ext_info, \
+}
+const struct iio_chan_spec dac8554_channels[] = {
+	DAC8554_CHANNEL(0),
+	DAC8554_CHANNEL(1),
+	DAC8554_CHANNEL(2),
+	DAC8554_CHANNEL(3),
+};
+#undef DAC8554_CHANNEL
+
+static int dac8554_probe(struct spi_device *spi)
+{
+	struct dac8554_state *st;
+	struct iio_dev *indio_dev;
+	int ret, voltage_uv = 0;
+	u32 addr;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->name = DAC8554_DRIVERNAME;
+	indio_dev->info = &dac8554_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = dac8554_channels;
+	indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
+
+	spi_set_drvdata(spi, indio_dev);
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		return ret;
+
+	st = iio_priv(indio_dev);
+
+	if (!spi->dev.of_node) {
+		dev_err(&spi->dev, "missing OF node");
+		return -ENODEV;
+	}
+	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
+	if (ret || addr > 2) {
+		dev_err(&spi->dev, "no or invalid chip address");
+		return -ENODEV;
+	}
+
+	st->spi = spi;
+	st->addr = addr;
+
+	st->reg = devm_regulator_get(&spi->dev, "vref");
+	if (IS_ERR(st->reg))
+		return PTR_ERR(st->reg);
+
+	ret = regulator_enable(st->reg);
+	if (ret)
+		return ret;
+
+	voltage_uv = regulator_get_voltage(st->reg);
+	if (voltage_uv < 0)
+		goto error_disable_reg;
+	st->vref_mv = voltage_uv / 1000;
+
+	ret = dac8554_powerdown_broadcast(st, DAC8554_PWRDN_100K);
+	if (ret)
+		goto error_disable_reg;
+
+	return 0;
+
+error_disable_reg:
+	regulator_disable(st->reg);
+	return ret;
+}
+
+static int dac8554_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct dac8554_state *st = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	regulator_disable(st->reg);
+
+	return 0;
+}
+
+static const struct of_device_id dac8554_of_match[] = {
+	{ .compatible = "ti,dac8554" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dac8554_of_match);
+
+static struct spi_driver dac8554_driver = {
+	.driver = {
+		.name = DAC8554_DRIVERNAME,
+		.owner = THIS_MODULE,
+		.of_match_table = dac8554_of_match,
+	 },
+	.probe = dac8554_probe,
+	.remove = dac8554_remove,
+};
+module_spi_driver(dac8554_driver);
+
+MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz@avionic-design.de>");
+MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
+MODULE_LICENSE("GPL v2");
-- 
2.1.3

Re: [PATCH 2/2] iio: add driver for the TI DAC8554

[Peter Meerwald]

> The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
> interface.

some minor comments below, looks good
 
> Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
> ---
>  drivers/iio/dac/Kconfig      |  10 ++
>  drivers/iio/dac/Makefile     |   1 +
>  drivers/iio/dac/ti-dac8554.c | 365 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 376 insertions(+)
>  create mode 100644 drivers/iio/dac/ti-dac8554.c
> 
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index 2236ea2..1689260 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -181,4 +181,14 @@ config MCP4922
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called mcp4922.
>  
> +config TI_DAC8554
> +	tristate "TI DAC8554 driver"
> +	depends on SPI
> +	depends on OF
> +	help
> +	  Say yes here to build the driver for the TI DAC8554.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called ti-dac8554.
> +
>  endmenu
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index 52be7e1..b98d79a 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -20,3 +20,4 @@ obj-$(CONFIG_MAX517) += max517.o
>  obj-$(CONFIG_MAX5821) += max5821.o
>  obj-$(CONFIG_MCP4725) += mcp4725.o
>  obj-$(CONFIG_MCP4922) += mcp4922.o
> +obj-$(CONFIG_TI_DAC8554) += ti-dac8554.o
> diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
> new file mode 100644
> index 0000000..9c135e1
> --- /dev/null
> +++ b/drivers/iio/dac/ti-dac8554.c
> @@ -0,0 +1,365 @@
> +/*
> + * TI DAC8554 Digital to Analog Converter SPI driver
> + *
> + * Copyright (C) 2014 Avionic Design GmbH
> + *
> + * Based on ad5446r_spi.c
> + * Copyright (C) 2010,2011 Analog Devices Inc.
> + *
> + * 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/spi/spi.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/module.h>
> +#include <linux/iio/iio.h>
> +#include <linux/of.h>
> +
> +#define DAC8554_DRIVERNAME			"ti-dac8554"
> +#define DAC8554_DAC_CHANNELS			4
> +
> +/* Load commands */
> +#define DAC8554_CMD_STORE_DAC_N			0x0
> +#define DAC8554_CMD_UPDATE_DAC_N		0x1
> +#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
> +#define DAC8554_CMD_UPDATE_BROADCAST		0x3
> +
> +#define DAC8554_BROADCAST_USE_SRDATA		0x2
> +/* Powerdown modes (ORed PD1|PD2 bits) */
> +#define DAC8554_PWRDN_HIZ			0x0
> +#define DAC8554_PWRDN_1K			0x1
> +#define DAC8554_PWRDN_100K			0x2
> +
> +#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
> +
> +/**
> + * struct dac8554_state - driver instance specific data
> + * @spi:		spi_device
> + * @reg:		supply regulator
> + * @addr:		two-bit chip address
> + * @vref_mv:		reference voltage in millivolt
> + * @val			DAC/channel data
> + * @powerdown		channel powerdown flag
> + * @powerdown_mode	channel powerdown mode
> + */
> +struct dac8554_state {
> +	struct spi_device		*spi;
> +	struct regulator		*reg;
> +	unsigned			addr;
> +	unsigned			vref_mv;
> +	u16				val[DAC8554_DAC_CHANNELS];
> +	bool				powerdown[DAC8554_DAC_CHANNELS];
> +	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
> +};
> +
> +static int dac8554_spi_write(struct spi_device *spi,
> +			     unsigned chip_addr, unsigned cmd,
> +			     unsigned chan_addr, unsigned val)
> +{
> +	u32 data;
> +	u8 msg[3];

careful with SPI; data should be ____cacheline_aligned

> +
> +	/*
> +	 * The input shift register is 24 bits wide. The 8 MSB are
> +	 * control bits, followed by 16 data bits.
> +	 * The first two bits A1 and A0 address a DAC8554 chip.
> +	 * The next two are the command bits, LD1 and LD0.
> +	 * After a don't-care-bit, the next two bits select the channel.
> +	 * The final control bit PD0 is a flag signalling if the data
> +	 * bits encode a powerdown mode. We merge PD0 with the adjacent
> +	 * data bits.
> +	 */
> +
> +	if (chip_addr > 3 || cmd > 3 || chan_addr > 3 ||
> +			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
> +		return -EINVAL;
> +
> +	data = (chip_addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
> +	msg[0] = data >> 16;
> +	msg[1] = data >> 8;
> +	msg[2] = data;
> +
> +	return spi_write(spi, msg, sizeof(msg));
> +}
> +
> +static int dac8554_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val,
> +			    int *val2,
> +			    long m)
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	switch (m) {
> +	case IIO_CHAN_INFO_RAW:
> +		*val = st->val[chan->address];
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = st->vref_mv;
> +		*val2 = 16;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	}
> +	return -EINVAL;
> +}
> +
> +static int dac8554_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int val,
> +			     int val2,
> +			     long mask)
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +	int err = 0;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (val > 0xffff || val < 0)
> +			return -EINVAL;
> +
> +		err = dac8554_spi_write(st->spi, st->addr,
> +				DAC8554_CMD_UPDATE_DAC_N,
> +				chan->address, val);
> +		if (err)
> +			return err;
> +
> +		st->val[chan->address] = val;
> +
> +		/* By hw design, DAC updates automatically trigger powerup. */
> +		st->powerdown[chan->address] = false;
> +
> +		return 0;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
> +				      const struct iio_chan_spec *chan)
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	return st->powerdown_mode[chan->address];
> +}
> +
> +static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
> +				      const struct iio_chan_spec *chan,
> +				      unsigned int mode)
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	st->powerdown_mode[chan->address] = mode;
> +
> +	return 0;
> +}
> +
> +static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
> +					  uintptr_t private,
> +					  const struct iio_chan_spec *chan,
> +					  char *buf)
> +{
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
> +}
> +
> +static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
> +					   uintptr_t private,
> +					   const struct iio_chan_spec *chan,
> +					   const char *buf,
> +					   size_t len)
> +{
> +	bool powerdown;
> +	int ret;
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +	u8 powerdown_mode;
> +
> +	ret = strtobool(buf, &powerdown);
> +	if (ret)
> +		return ret;
> +
> +	st->powerdown[chan->address] = powerdown;
> +
> +	if (powerdown) {
> +		powerdown_mode = st->powerdown_mode[chan->address];
> +		ret = dac8554_spi_write(st->spi, st->addr,
> +				DAC8554_CMD_UPDATE_DAC_N,
> +				chan->address,
> +				DAC8554_PWRDN_TO_SR(powerdown_mode));
> +	} else {
> +		/* Load DAC with cached value. This triggers a powerup. */
> +		ret = dac8554_spi_write(st->spi, st->addr,
> +				DAC8554_CMD_UPDATE_DAC_N,
> +				chan->address,
> +				st->val[chan->address]);
> +	}
> +
> +	if (ret)
> +		return ret;
> +
> +	return len;
> +}
> +
> +static int dac8554_powerdown_broadcast(struct dac8554_state *st,
> +				       u8 powerdown_mode)
> +{
> +	int ret;
> +
> +	ret = dac8554_spi_write(st->spi, 0,
> +			DAC8554_CMD_UPDATE_BROADCAST,
> +			DAC8554_BROADCAST_USE_SRDATA,
> +			DAC8554_PWRDN_TO_SR(powerdown_mode));
> +	if (ret)
> +		return ret;
> +
> +	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
> +	memset(st->powerdown, true, sizeof(st->powerdown));
> +
> +	return 0;
> +}
> +
> +static const struct iio_info dac8554_info = {
> +	.write_raw = dac8554_write_raw,
> +	.read_raw = dac8554_read_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static const char * const dac8554_powerdown_modes[] = {
> +	"hi-z",

hi-z is (not yet) described in ABI/testing/sysfs-bus-iio, you should add 
that

> +	"1kohm_to_gnd",
> +	"100kohm_to_gnd"
> +};
> +
> +static const struct iio_enum dac8854_powerdown_mode_enum = {
> +	.items = dac8554_powerdown_modes,
> +	.num_items = ARRAY_SIZE(dac8554_powerdown_modes),
> +	.get = dac8554_get_powerdown_mode,
> +	.set = dac8554_set_powerdown_mode,
> +};
> +
> +static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
> +	{
> +		.name = "powerdown",
> +		.read = dac8554_read_dac_powerdown,
> +		.write = dac8554_write_dac_powerdown,
> +		.shared = IIO_SEPARATE,
> +	},
> +	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
> +		 &dac8854_powerdown_mode_enum),
> +	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
> +	{ },
> +};
> +
> +#define DAC8554_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), \
> +	.ext_info = dac8554_ext_info, \
> +}
> +const struct iio_chan_spec dac8554_channels[] = {
> +	DAC8554_CHANNEL(0),
> +	DAC8554_CHANNEL(1),
> +	DAC8554_CHANNEL(2),
> +	DAC8554_CHANNEL(3),
> +};
> +#undef DAC8554_CHANNEL

nothing wrong, but this would be the first IIO driver to #undef its 
channel macro

> +
> +static int dac8554_probe(struct spi_device *spi)
> +{
> +	struct dac8554_state *st;
> +	struct iio_dev *indio_dev;
> +	int ret, voltage_uv = 0;
> +	u32 addr;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->name = DAC8554_DRIVERNAME;
> +	indio_dev->info = &dac8554_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = dac8554_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
> +
> +	spi_set_drvdata(spi, indio_dev);
> +	ret = iio_device_register(indio_dev);

iio_device_register() should probably be the last thing in _probe();
_state should be fully set up so requests can be handled

> +	if (ret)
> +		return ret;
> +
> +	st = iio_priv(indio_dev);
> +
> +	if (!spi->dev.of_node) {
> +		dev_err(&spi->dev, "missing OF node");
> +		return -ENODEV;
> +	}
> +	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
> +	if (ret || addr > 2) {

addr < 0?

> +		dev_err(&spi->dev, "no or invalid chip address");
> +		return -ENODEV;
> +	}
> +
> +	st->spi = spi;
> +	st->addr = addr;
> +
> +	st->reg = devm_regulator_get(&spi->dev, "vref");
> +	if (IS_ERR(st->reg))
> +		return PTR_ERR(st->reg);
> +
> +	ret = regulator_enable(st->reg);
> +	if (ret)
> +		return ret;
> +
> +	voltage_uv = regulator_get_voltage(st->reg);
> +	if (voltage_uv < 0)
> +		goto error_disable_reg;
> +	st->vref_mv = voltage_uv / 1000;
> +
> +	ret = dac8554_powerdown_broadcast(st, DAC8554_PWRDN_100K);
> +	if (ret)
> +		goto error_disable_reg;
> +
> +	return 0;
> +
> +error_disable_reg:
> +	regulator_disable(st->reg);
> +	return ret;
> +}
> +
> +static int dac8554_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct dac8554_state *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);

probably a powerdown?

> +	regulator_disable(st->reg);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id dac8554_of_match[] = {
> +	{ .compatible = "ti,dac8554" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, dac8554_of_match);
> +
> +static struct spi_driver dac8554_driver = {
> +	.driver = {
> +		.name = DAC8554_DRIVERNAME,
> +		.owner = THIS_MODULE,
> +		.of_match_table = dac8554_of_match,
> +	 },
> +	.probe = dac8554_probe,
> +	.remove = dac8554_remove,
> +};
> +module_spi_driver(dac8554_driver);
> +
> +MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz@avionic-design.de>");
> +MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)

Re: [PATCH 2/2] iio: add driver for the TI DAC8554

[Lars-Peter Clausen]

On 11/20/2014 07:19 PM, Peter Meerwald wrote:

>> +static const char * const dac8554_powerdown_modes[] = {
>> +	"hi-z",
>
> hi-z is (not yet) described in ABI/testing/sysfs-bus-iio, you should add
> that

Other drivers call it three_state, so might as well stay with that.

>
>> +	"1kohm_to_gnd",
>> +	"100kohm_to_gnd"
>> +};

Re: [PATCH 2/2] iio: add driver for the TI DAC8554

[Nikolaus Schulz]

On Thu, Nov 20, 2014 at 07:19:36PM +0100, Peter Meerwald wrote:
> 
> > The TI DAC8554 is a quad-channel Digital-to-Analog Converter with an SPI
> > interface.
> 
> some minor comments below, looks good
>  
> > Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
> > ---
> >  drivers/iio/dac/Kconfig      |  10 ++
> >  drivers/iio/dac/Makefile     |   1 +
> >  drivers/iio/dac/ti-dac8554.c | 365 +++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 376 insertions(+)
> >  create mode 100644 drivers/iio/dac/ti-dac8554.c
> > 
> > diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> > index 2236ea2..1689260 100644
> > --- a/drivers/iio/dac/Kconfig
> > +++ b/drivers/iio/dac/Kconfig
> > @@ -181,4 +181,14 @@ config MCP4922
> >  	  To compile this driver as a module, choose M here: the module
> >  	  will be called mcp4922.
> >  
> > +config TI_DAC8554
> > +	tristate "TI DAC8554 driver"
> > +	depends on SPI
> > +	depends on OF
> > +	help
> > +	  Say yes here to build the driver for the TI DAC8554.
> > +
> > +	  To compile this driver as a module, choose M here: the module
> > +	  will be called ti-dac8554.
> > +
> >  endmenu
> > diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> > index 52be7e1..b98d79a 100644
> > --- a/drivers/iio/dac/Makefile
> > +++ b/drivers/iio/dac/Makefile
> > @@ -20,3 +20,4 @@ obj-$(CONFIG_MAX517) += max517.o
> >  obj-$(CONFIG_MAX5821) += max5821.o
> >  obj-$(CONFIG_MCP4725) += mcp4725.o
> >  obj-$(CONFIG_MCP4922) += mcp4922.o
> > +obj-$(CONFIG_TI_DAC8554) += ti-dac8554.o
> > diff --git a/drivers/iio/dac/ti-dac8554.c b/drivers/iio/dac/ti-dac8554.c
> > new file mode 100644
> > index 0000000..9c135e1
> > --- /dev/null
> > +++ b/drivers/iio/dac/ti-dac8554.c
> > @@ -0,0 +1,365 @@
> > +/*
> > + * TI DAC8554 Digital to Analog Converter SPI driver
> > + *
> > + * Copyright (C) 2014 Avionic Design GmbH
> > + *
> > + * Based on ad5446r_spi.c
> > + * Copyright (C) 2010,2011 Analog Devices Inc.
> > + *
> > + * 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/spi/spi.h>
> > +#include <linux/regulator/consumer.h>
> > +#include <linux/module.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/of.h>
> > +
> > +#define DAC8554_DRIVERNAME			"ti-dac8554"
> > +#define DAC8554_DAC_CHANNELS			4
> > +
> > +/* Load commands */
> > +#define DAC8554_CMD_STORE_DAC_N			0x0
> > +#define DAC8554_CMD_UPDATE_DAC_N		0x1
> > +#define DAC8554_CMD_STORE_DAC_N_UPDATE_ALL	0x2
> > +#define DAC8554_CMD_UPDATE_BROADCAST		0x3
> > +
> > +#define DAC8554_BROADCAST_USE_SRDATA		0x2
> > +/* Powerdown modes (ORed PD1|PD2 bits) */
> > +#define DAC8554_PWRDN_HIZ			0x0
> > +#define DAC8554_PWRDN_1K			0x1
> > +#define DAC8554_PWRDN_100K			0x2
> > +
> > +#define DAC8554_PWRDN_TO_SR(mode)		(BIT(16) | (mode) << 14)
> > +
> > +/**
> > + * struct dac8554_state - driver instance specific data
> > + * @spi:		spi_device
> > + * @reg:		supply regulator
> > + * @addr:		two-bit chip address
> > + * @vref_mv:		reference voltage in millivolt
> > + * @val			DAC/channel data
> > + * @powerdown		channel powerdown flag
> > + * @powerdown_mode	channel powerdown mode
> > + */
> > +struct dac8554_state {
> > +	struct spi_device		*spi;
> > +	struct regulator		*reg;
> > +	unsigned			addr;
> > +	unsigned			vref_mv;
> > +	u16				val[DAC8554_DAC_CHANNELS];
> > +	bool				powerdown[DAC8554_DAC_CHANNELS];
> > +	u8				powerdown_mode[DAC8554_DAC_CHANNELS];
> > +};
> > +
> > +static int dac8554_spi_write(struct spi_device *spi,
> > +			     unsigned chip_addr, unsigned cmd,
> > +			     unsigned chan_addr, unsigned val)
> > +{
> > +	u32 data;
> > +	u8 msg[3];
> 
> careful with SPI; data should be ____cacheline_aligned

Ah, thanks.  Actually for DMA, it also shouldn't be on the stack.  I'll
move it into struct dac8554_state, just like the majority of ad* DAC
drivers do.

Looking at the other iio dac drivers, ad5624r_spi and ad5446 also
use unaligned memory on the stack for SPI transfers, and need be fixed
as well.

> > +
> > +	/*
> > +	 * The input shift register is 24 bits wide. The 8 MSB are
> > +	 * control bits, followed by 16 data bits.
> > +	 * The first two bits A1 and A0 address a DAC8554 chip.
> > +	 * The next two are the command bits, LD1 and LD0.
> > +	 * After a don't-care-bit, the next two bits select the channel.
> > +	 * The final control bit PD0 is a flag signalling if the data
> > +	 * bits encode a powerdown mode. We merge PD0 with the adjacent
> > +	 * data bits.
> > +	 */
> > +
> > +	if (chip_addr > 3 || cmd > 3 || chan_addr > 3 ||
> > +			(val > 0xffff && (val & ~DAC8554_PWRDN_TO_SR(3))))
> > +		return -EINVAL;
> > +
> > +	data = (chip_addr << 22) | (cmd << 20) | (chan_addr << 17) | val;
> > +	msg[0] = data >> 16;
> > +	msg[1] = data >> 8;
> > +	msg[2] = data;
> > +
> > +	return spi_write(spi, msg, sizeof(msg));
> > +}
> > +
> > +static int dac8554_read_raw(struct iio_dev *indio_dev,
> > +			    struct iio_chan_spec const *chan,
> > +			    int *val,
> > +			    int *val2,
> > +			    long m)
> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	switch (m) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		*val = st->val[chan->address];
> > +		return IIO_VAL_INT;
> > +	case IIO_CHAN_INFO_SCALE:
> > +		*val = st->vref_mv;
> > +		*val2 = 16;
> > +		return IIO_VAL_FRACTIONAL_LOG2;
> > +	}
> > +	return -EINVAL;
> > +}
> > +
> > +static int dac8554_write_raw(struct iio_dev *indio_dev,
> > +			     struct iio_chan_spec const *chan,
> > +			     int val,
> > +			     int val2,
> > +			     long mask)
> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +	int err = 0;
> > +
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		if (val > 0xffff || val < 0)
> > +			return -EINVAL;
> > +
> > +		err = dac8554_spi_write(st->spi, st->addr,
> > +				DAC8554_CMD_UPDATE_DAC_N,
> > +				chan->address, val);
> > +		if (err)
> > +			return err;
> > +
> > +		st->val[chan->address] = val;
> > +
> > +		/* By hw design, DAC updates automatically trigger powerup. */
> > +		st->powerdown[chan->address] = false;
> > +
> > +		return 0;
> > +
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> > +static int dac8554_get_powerdown_mode(struct iio_dev *indio_dev,
> > +				      const struct iio_chan_spec *chan)
> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	return st->powerdown_mode[chan->address];
> > +}
> > +
> > +static int dac8554_set_powerdown_mode(struct iio_dev *indio_dev,
> > +				      const struct iio_chan_spec *chan,
> > +				      unsigned int mode)
> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	st->powerdown_mode[chan->address] = mode;
> > +
> > +	return 0;
> > +}
> > +
> > +static ssize_t dac8554_read_dac_powerdown(struct iio_dev *indio_dev,
> > +					  uintptr_t private,
> > +					  const struct iio_chan_spec *chan,
> > +					  char *buf)
> > +{
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	return sprintf(buf, "%d\n", st->powerdown[chan->address]);
> > +}
> > +
> > +static ssize_t dac8554_write_dac_powerdown(struct iio_dev *indio_dev,
> > +					   uintptr_t private,
> > +					   const struct iio_chan_spec *chan,
> > +					   const char *buf,
> > +					   size_t len)
> > +{
> > +	bool powerdown;
> > +	int ret;
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +	u8 powerdown_mode;
> > +
> > +	ret = strtobool(buf, &powerdown);
> > +	if (ret)
> > +		return ret;
> > +
> > +	st->powerdown[chan->address] = powerdown;
> > +
> > +	if (powerdown) {
> > +		powerdown_mode = st->powerdown_mode[chan->address];
> > +		ret = dac8554_spi_write(st->spi, st->addr,
> > +				DAC8554_CMD_UPDATE_DAC_N,
> > +				chan->address,
> > +				DAC8554_PWRDN_TO_SR(powerdown_mode));
> > +	} else {
> > +		/* Load DAC with cached value. This triggers a powerup. */
> > +		ret = dac8554_spi_write(st->spi, st->addr,
> > +				DAC8554_CMD_UPDATE_DAC_N,
> > +				chan->address,
> > +				st->val[chan->address]);
> > +	}
> > +
> > +	if (ret)
> > +		return ret;
> > +
> > +	return len;
> > +}
> > +
> > +static int dac8554_powerdown_broadcast(struct dac8554_state *st,
> > +				       u8 powerdown_mode)
> > +{
> > +	int ret;
> > +
> > +	ret = dac8554_spi_write(st->spi, 0,
> > +			DAC8554_CMD_UPDATE_BROADCAST,
> > +			DAC8554_BROADCAST_USE_SRDATA,
> > +			DAC8554_PWRDN_TO_SR(powerdown_mode));
> > +	if (ret)
> > +		return ret;
> > +
> > +	memset(st->powerdown_mode, powerdown_mode, sizeof(st->powerdown_mode));
> > +	memset(st->powerdown, true, sizeof(st->powerdown));
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct iio_info dac8554_info = {
> > +	.write_raw = dac8554_write_raw,
> > +	.read_raw = dac8554_read_raw,
> > +	.driver_module = THIS_MODULE,
> > +};
> > +
> > +static const char * const dac8554_powerdown_modes[] = {
> > +	"hi-z",
> 
> hi-z is (not yet) described in ABI/testing/sysfs-bus-iio, you should add 
> that

I'll switch that to "three_state", as suggested by Lars-Peter.

> > +	"1kohm_to_gnd",
> > +	"100kohm_to_gnd"
> > +};
> > +
> > +static const struct iio_enum dac8854_powerdown_mode_enum = {
> > +	.items = dac8554_powerdown_modes,
> > +	.num_items = ARRAY_SIZE(dac8554_powerdown_modes),
> > +	.get = dac8554_get_powerdown_mode,
> > +	.set = dac8554_set_powerdown_mode,
> > +};
> > +
> > +static const struct iio_chan_spec_ext_info dac8554_ext_info[] = {
> > +	{
> > +		.name = "powerdown",
> > +		.read = dac8554_read_dac_powerdown,
> > +		.write = dac8554_write_dac_powerdown,
> > +		.shared = IIO_SEPARATE,
> > +	},
> > +	IIO_ENUM("powerdown_mode", IIO_SEPARATE,
> > +		 &dac8854_powerdown_mode_enum),
> > +	IIO_ENUM_AVAILABLE("powerdown_mode", &dac8854_powerdown_mode_enum),
> > +	{ },
> > +};
> > +
> > +#define DAC8554_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), \
> > +	.ext_info = dac8554_ext_info, \
> > +}
> > +const struct iio_chan_spec dac8554_channels[] = {
> > +	DAC8554_CHANNEL(0),
> > +	DAC8554_CHANNEL(1),
> > +	DAC8554_CHANNEL(2),
> > +	DAC8554_CHANNEL(3),
> > +};
> > +#undef DAC8554_CHANNEL
> 
> nothing wrong, but this would be the first IIO driver to #undef its 
> channel macro

Hehe. Ok, one might argue that #undef'ing it simply adds noise for
nothing substantial...

> > +
> > +static int dac8554_probe(struct spi_device *spi)
> > +{
> > +	struct dac8554_state *st;
> > +	struct iio_dev *indio_dev;
> > +	int ret, voltage_uv = 0;
> > +	u32 addr;
> > +
> > +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> > +	if (!indio_dev)
> > +		return -ENOMEM;
> > +
> > +	indio_dev->dev.parent = &spi->dev;
> > +	indio_dev->name = DAC8554_DRIVERNAME;
> > +	indio_dev->info = &dac8554_info;
> > +	indio_dev->modes = INDIO_DIRECT_MODE;
> > +	indio_dev->channels = dac8554_channels;
> > +	indio_dev->num_channels = ARRAY_SIZE(dac8554_channels);
> > +
> > +	spi_set_drvdata(spi, indio_dev);
> > +	ret = iio_device_register(indio_dev);
> 
> iio_device_register() should probably be the last thing in _probe();
> _state should be fully set up so requests can be handled

Ok.

> > +	if (ret)
> > +		return ret;
> > +
> > +	st = iio_priv(indio_dev);
> > +
> > +	if (!spi->dev.of_node) {
> > +		dev_err(&spi->dev, "missing OF node");
> > +		return -ENODEV;
> > +	}
> > +	ret = of_property_read_u32(spi->dev.of_node, "address", &addr);
> > +	if (ret || addr > 2) {
> 
> addr < 0?

Ah! Yes.

> > +		dev_err(&spi->dev, "no or invalid chip address");
> > +		return -ENODEV;
> > +	}
> > +
> > +	st->spi = spi;
> > +	st->addr = addr;
> > +
> > +	st->reg = devm_regulator_get(&spi->dev, "vref");
> > +	if (IS_ERR(st->reg))
> > +		return PTR_ERR(st->reg);
> > +
> > +	ret = regulator_enable(st->reg);
> > +	if (ret)
> > +		return ret;
> > +
> > +	voltage_uv = regulator_get_voltage(st->reg);
> > +	if (voltage_uv < 0)
> > +		goto error_disable_reg;
> > +	st->vref_mv = voltage_uv / 1000;
> > +
> > +	ret = dac8554_powerdown_broadcast(st, DAC8554_PWRDN_100K);
> > +	if (ret)
> > +		goto error_disable_reg;
> > +
> > +	return 0;
> > +
> > +error_disable_reg:
> > +	regulator_disable(st->reg);
> > +	return ret;
> > +}
> > +
> > +static int dac8554_remove(struct spi_device *spi)
> > +{
> > +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> > +	struct dac8554_state *st = iio_priv(indio_dev);
> > +
> > +	iio_device_unregister(indio_dev);
> 
> probably a powerdown?

It's powered down anyway by disabling the regulator, isnt' it?

> > +	regulator_disable(st->reg);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct of_device_id dac8554_of_match[] = {
> > +	{ .compatible = "ti,dac8554" },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(of, dac8554_of_match);
> > +
> > +static struct spi_driver dac8554_driver = {
> > +	.driver = {
> > +		.name = DAC8554_DRIVERNAME,
> > +		.owner = THIS_MODULE,
> > +		.of_match_table = dac8554_of_match,
> > +	 },
> > +	.probe = dac8554_probe,
> > +	.remove = dac8554_remove,
> > +};
> > +module_spi_driver(dac8554_driver);
> > +
> > +MODULE_AUTHOR("Nikolaus Schulz <nikolaus.schulz@avionic-design.de>");
> > +MODULE_DESCRIPTION("Texas Instruments DAC8554 SPI driver");
> > +MODULE_LICENSE("GPL v2");
> > 
> 
> -- 
> 
> Peter Meerwald
> +43-664-2444418 (mobile)

Thanks for the review!

-- 
Avionic Design GmbH
Nikolaus Schulz
Wragekamp 10
D-22397 Hamburg
Germany

Tel.:  +49 40 88187-163
Fax:   +49 40 88187-150
Email: nikolaus.schulz@avionic-design.de

Avionic Design GmbH
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