iio: dac: add support for stm32 DAC

Add support for STMicroelectronics STM32 DAC. It's a 12-bit, voltage
output digital-to-analog converter. It has two output channels, each
with its own converter.
It supports 8 bits or 12bits left/right aligned data format. Only
12bits right-aligned is used here. It has built-in noise or
triangle waveform generator, and supports external triggers for
conversions.
Each channel can be used independently, with separate trigger, then
separate IIO devices are used to handle this. Core driver is intended
to share common resources such as clock, reset, reference voltage and
registers.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 334 insertions, 0 deletions

diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
new file mode 100644
index 000000000000..50f8ec091058
--- /dev/null
+++ b/drivers/iio/dac/stm32-dac.c
@@ -0,0 +1,334 @@
+/*
+ * This file is part of STM32 DAC driver
+ *
+ * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
+ * Authors: Amelie Delaunay <amelie.delaunay@st.com>
+ *	    Fabrice Gasnier <fabrice.gasnier@st.com>
+ *
+ * License type: GPLv2
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/iio/iio.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include "stm32-dac-core.h"
+
+#define STM32_DAC_CHANNEL_1		1
+#define STM32_DAC_CHANNEL_2		2
+#define STM32_DAC_IS_CHAN_1(ch)		((ch) & STM32_DAC_CHANNEL_1)
+
+/**
+ * struct stm32_dac - private data of DAC driver
+ * @common:		reference to DAC common data
+ */
+struct stm32_dac {
+	struct stm32_dac_common *common;
+};
+
+static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
+{
+	struct stm32_dac *dac = iio_priv(indio_dev);
+	u32 en, val;
+	int ret;
+
+	ret = regmap_read(dac->common->regmap, STM32_DAC_CR, &val);
+	if (ret < 0)
+		return ret;
+	if (STM32_DAC_IS_CHAN_1(channel))
+		en = FIELD_GET(STM32_DAC_CR_EN1, val);
+	else
+		en = FIELD_GET(STM32_DAC_CR_EN2, val);
+
+	return !!en;
+}
+
+static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
+				      bool enable)
+{
+	struct stm32_dac *dac = iio_priv(indio_dev);
+	u32 msk = STM32_DAC_IS_CHAN_1(ch) ? STM32_DAC_CR_EN1 : STM32_DAC_CR_EN2;
+	u32 en = enable ? msk : 0;
+	int ret;
+
+	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
+	if (ret < 0) {
+		dev_err(&indio_dev->dev, "%s failed\n", en ?
+			"Enable" : "Disable");
+		return ret;
+	}
+
+	/*
+	 * When HFSEL is set, it is not allowed to write the DHRx register
+	 * during 8 clock cycles after the ENx bit is set. It is not allowed
+	 * to make software/hardware trigger during this period either.
+	 */
+	if (en && dac->common->hfsel)
+		udelay(1);
+
+	return 0;
+}
+
+static int stm32_dac_get_value(struct stm32_dac *dac, int channel, int *val)
+{
+	int ret;
+
+	if (STM32_DAC_IS_CHAN_1(channel))
+		ret = regmap_read(dac->common->regmap, STM32_DAC_DOR1, val);
+	else
+		ret = regmap_read(dac->common->regmap, STM32_DAC_DOR2, val);
+
+	return ret ? ret : IIO_VAL_INT;
+}
+
+static int stm32_dac_set_value(struct stm32_dac *dac, int channel, int val)
+{
+	int ret;
+
+	if (STM32_DAC_IS_CHAN_1(channel))
+		ret = regmap_write(dac->common->regmap, STM32_DAC_DHR12R1, val);
+	else
+		ret = regmap_write(dac->common->regmap, STM32_DAC_DHR12R2, val);
+
+	return ret;
+}
+
+static int stm32_dac_read_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      int *val, int *val2, long mask)
+{
+	struct stm32_dac *dac = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		return stm32_dac_get_value(dac, chan->channel, val);
+	case IIO_CHAN_INFO_SCALE:
+		*val = dac->common->vref_mv;
+		*val2 = chan->scan_type.realbits;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int stm32_dac_write_raw(struct iio_dev *indio_dev,
+			       struct iio_chan_spec const *chan,
+			       int val, int val2, long mask)
+{
+	struct stm32_dac *dac = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		return stm32_dac_set_value(dac, chan->channel, val);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int stm32_dac_debugfs_reg_access(struct iio_dev *indio_dev,
+					unsigned reg, unsigned writeval,
+					unsigned *readval)
+{
+	struct stm32_dac *dac = iio_priv(indio_dev);
+
+	if (!readval)
+		return regmap_write(dac->common->regmap, reg, writeval);
+	else
+		return regmap_read(dac->common->regmap, reg, readval);
+}
+
+static const struct iio_info stm32_dac_iio_info = {
+	.read_raw = stm32_dac_read_raw,
+	.write_raw = stm32_dac_write_raw,
+	.debugfs_reg_access = stm32_dac_debugfs_reg_access,
+	.driver_module = THIS_MODULE,
+};
+
+static const char * const stm32_dac_powerdown_modes[] = {
+	"three_state",
+};
+
+static int stm32_dac_get_powerdown_mode(struct iio_dev *indio_dev,
+					const struct iio_chan_spec *chan)
+{
+	return 0;
+}
+
+static int stm32_dac_set_powerdown_mode(struct iio_dev *indio_dev,
+					const struct iio_chan_spec *chan,
+					unsigned int type)
+{
+	return 0;
+}
+
+static ssize_t stm32_dac_read_powerdown(struct iio_dev *indio_dev,
+					uintptr_t private,
+					const struct iio_chan_spec *chan,
+					char *buf)
+{
+	int ret = stm32_dac_is_enabled(indio_dev, chan->channel);
+
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "%d\n", ret ? 0 : 1);
+}
+
+static ssize_t stm32_dac_write_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;
+
+	ret = strtobool(buf, &powerdown);
+	if (ret)
+		return ret;
+
+	ret = stm32_dac_set_enable_state(indio_dev, chan->channel, !powerdown);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static const struct iio_enum stm32_dac_powerdown_mode_en = {
+	.items = stm32_dac_powerdown_modes,
+	.num_items = ARRAY_SIZE(stm32_dac_powerdown_modes),
+	.get = stm32_dac_get_powerdown_mode,
+	.set = stm32_dac_set_powerdown_mode,
+};
+
+static const struct iio_chan_spec_ext_info stm32_dac_ext_info[] = {
+	{
+		.name = "powerdown",
+		.read = stm32_dac_read_powerdown,
+		.write = stm32_dac_write_powerdown,
+		.shared = IIO_SEPARATE,
+	},
+	IIO_ENUM("powerdown_mode", IIO_SEPARATE, &stm32_dac_powerdown_mode_en),
+	IIO_ENUM_AVAILABLE("powerdown_mode", &stm32_dac_powerdown_mode_en),
+	{},
+};
+
+#define STM32_DAC_CHANNEL(chan, name) {			\
+	.type = IIO_VOLTAGE,				\
+	.indexed = 1,					\
+	.output = 1,					\
+	.channel = chan,				\
+	.info_mask_separate =				\
+		BIT(IIO_CHAN_INFO_RAW) |		\
+		BIT(IIO_CHAN_INFO_SCALE),		\
+	/* scan_index is always 0 as num_channels is 1 */ \
+	.scan_type = {					\
+		.sign = 'u',				\
+		.realbits = 12,				\
+		.storagebits = 16,			\
+	},						\
+	.datasheet_name = name,				\
+	.ext_info = stm32_dac_ext_info			\
+}
+
+static const struct iio_chan_spec stm32_dac_channels[] = {
+	STM32_DAC_CHANNEL(STM32_DAC_CHANNEL_1, "out1"),
+	STM32_DAC_CHANNEL(STM32_DAC_CHANNEL_2, "out2"),
+};
+
+static int stm32_dac_chan_of_init(struct iio_dev *indio_dev)
+{
+	struct device_node *np = indio_dev->dev.of_node;
+	unsigned int i;
+	u32 channel;
+	int ret;
+
+	ret = of_property_read_u32(np, "reg", &channel);
+	if (ret) {
+		dev_err(&indio_dev->dev, "Failed to read reg property\n");
+		return ret;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(stm32_dac_channels); i++) {
+		if (stm32_dac_channels[i].channel == channel)
+			break;
+	}
+	if (i >= ARRAY_SIZE(stm32_dac_channels)) {
+		dev_err(&indio_dev->dev, "Invalid st,dac-channel\n");
+		return -EINVAL;
+	}
+
+	indio_dev->channels = &stm32_dac_channels[i];
+	/*
+	 * Expose only one channel here, as they can be used independently,
+	 * with separate trigger. Then separate IIO devices are instantiated
+	 * to manage this.
+	 */
+	indio_dev->num_channels = 1;
+
+	return 0;
+};
+
+static int stm32_dac_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct iio_dev *indio_dev;
+	struct stm32_dac *dac;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*dac));
+	if (!indio_dev)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, indio_dev);
+
+	dac = iio_priv(indio_dev);
+	dac->common = dev_get_drvdata(pdev->dev.parent);
+	indio_dev->name = dev_name(&pdev->dev);
+	indio_dev->dev.parent = &pdev->dev;
+	indio_dev->dev.of_node = pdev->dev.of_node;
+	indio_dev->info = &stm32_dac_iio_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	ret = stm32_dac_chan_of_init(indio_dev);
+	if (ret < 0)
+		return ret;
+
+	return devm_iio_device_register(&pdev->dev, indio_dev);
+}
+
+static const struct of_device_id stm32_dac_of_match[] = {
+	{ .compatible = "st,stm32-dac", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm32_dac_of_match);
+
+static struct platform_driver stm32_dac_driver = {
+	.probe = stm32_dac_probe,
+	.driver = {
+		.name = "stm32-dac",
+		.of_match_table = stm32_dac_of_match,
+	},
+};
+module_platform_driver(stm32_dac_driver);
+
+MODULE_ALIAS("platform:stm32-dac");
+MODULE_AUTHOR("Amelie Delaunay <amelie.delaunay@st.com>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 DAC driver");
+MODULE_LICENSE("GPL v2");