[PATCH] iio: potentiometer: Add driver for Microchip MCP41xxx/42xxx

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This patch adds driver support for the Microchip MCP41xxx/42xxx family
of digital potentiometers:

DEVICE      Wipers  Positions   Resistance (kOhm)
MCP41010    1       256         10
MCP41050    1       256         50
MCP41100    1       256         100
MCP42010    2       256         10
MCP42050    2       256         50
MCP42100    2       256         100

Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/11195c.pdf

Signed-off-by: Chris Coffey <cmc@xxxxxxxxxxxxx>
---
 .../bindings/iio/potentiometer/mcp41010.txt        |  29 +++
 drivers/iio/potentiometer/Kconfig                  |  12 ++
 drivers/iio/potentiometer/Makefile                 |   1 +
 drivers/iio/potentiometer/mcp41010.c               | 216 +++++++++++++++++++++
 4 files changed, 258 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt
 create mode 100644 drivers/iio/potentiometer/mcp41010.c

diff --git a/Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt b/Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt
new file mode 100644
index 0000000000..17565acace
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt
@@ -0,0 +1,29 @@
+* Microchip MCP41010/41050/41100/42010/42050/42100 Digital Potentiometer
+  driver
+
+Datasheet publicly available at:
+http://ww1.microchip.com/downloads/en/devicedoc/11195c.pdf
+
+The node for this driver must be a child node of a SPI controller, hence
+all mandatory properties described in
+
+        Documentation/devicetree/bindings/spi/spi-bus.txt
+
+must be specified.
+
+Required properties:
+	- compatible:  	Must be one of the following, depending on the
+			model:
+			"microchip,mcp41010"
+			"microchip,mcp41050"
+			"microchip,mcp41100"
+			"microchip,mcp42010"
+			"microchip,mcp42050"
+			"microchip,mcp42100"
+
+Example:
+mcp41010: potentiometer@0 {
+	compatible = "mcp41010";
+	reg = <0>;
+	spi-max-frequency = <500000>;
+};
diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
index 79ec2eba49..6303cbe799 100644
--- a/drivers/iio/potentiometer/Kconfig
+++ b/drivers/iio/potentiometer/Kconfig
@@ -90,6 +90,18 @@ config MCP4531
 	  To compile this driver as a module, choose M here: the
 	  module will be called mcp4531.
 
+config MCP41010
+	tristate "Microchip MCP41xxx/MCP42xxx Digital Potentiometer driver"
+	depends on SPI
+	help
+	  Say yes here to build support for the Microchip
+	  MCP41010, MCP41050, MCP41100,
+	  MCP42010, MCP42050, MCP42100
+	  digital potentiometer chips.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mcp41010.
+
 config TPL0102
 	tristate "Texas Instruments digital potentiometer driver"
 	depends on I2C
diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
index 4af657883c..8ff55138cf 100644
--- a/drivers/iio/potentiometer/Makefile
+++ b/drivers/iio/potentiometer/Makefile
@@ -11,4 +11,5 @@ obj-$(CONFIG_MAX5487) += max5487.o
 obj-$(CONFIG_MCP4018) += mcp4018.o
 obj-$(CONFIG_MCP4131) += mcp4131.o
 obj-$(CONFIG_MCP4531) += mcp4531.o
+obj-$(CONFIG_MCP41010) += mcp41010.o
 obj-$(CONFIG_TPL0102) += tpl0102.o
diff --git a/drivers/iio/potentiometer/mcp41010.c b/drivers/iio/potentiometer/mcp41010.c
new file mode 100644
index 0000000000..4068e8eb57
--- /dev/null
+++ b/drivers/iio/potentiometer/mcp41010.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Industrial I/O driver for Microchip digital potentiometers
+ *
+ * Copyright (c) 2018 Chris Coffey <cmc@xxxxxxxxxxxxx>
+ * Based on: Slawomir Stepien's code from mcp4131.c
+ *
+ * Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/11195c.pdf
+ *
+ * DEVID	#Wipers	#Positions	Resistance (kOhm)
+ * mcp41010	1	256		10
+ * mcp41050	1	256		50
+ * mcp41100	1	256		100
+ * mcp42010	2	256		10
+ * mcp42050	2	256		50
+ * mcp42100	2	256		100
+ *
+ */
+
+#include <linux/cache.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/spi/spi.h>
+
+#define MCP41010_MAX_WIPERS	2
+#define MCP41010_WRITE		(0x01 << 4)
+#define MCP41010_WIPER_MAX	255
+#define MCP41010_WIPER_ENABLE	BIT(0)
+
+struct mcp41010_cfg {
+	int wipers;
+	int kohms;
+};
+
+enum mcp41010_type {
+	MCP41010 = 0,
+	MCP41050,
+	MCP41100,
+	MCP42010,
+	MCP42050,
+	MCP42100,
+};
+
+static const struct mcp41010_cfg mcp41010_cfg[] = {
+	[MCP41010] = { .wipers = 1, .kohms =  10, },
+	[MCP41050] = { .wipers = 1, .kohms =  50, },
+	[MCP41100] = { .wipers = 1, .kohms = 100, },
+	[MCP42010] = { .wipers = 2, .kohms =  10, },
+	[MCP42050] = { .wipers = 2, .kohms =  50, },
+	[MCP42100] = { .wipers = 2, .kohms = 100, },
+};
+
+struct mcp41010_data {
+	struct spi_device *spi;
+	const struct mcp41010_cfg *cfg;
+	struct mutex lock; /* Protect write sequences */
+	unsigned int value[MCP41010_MAX_WIPERS]; /* Cache wiper values */
+	u8 buf[2] ____cacheline_aligned;
+};
+
+#define MCP41010_CHANNEL(ch) {					\
+	.type = IIO_RESISTANCE,					\
+	.indexed = 1,						\
+	.output = 1,						\
+	.channel = (ch),					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+}
+
+static const struct iio_chan_spec mcp41010_channels[] = {
+	MCP41010_CHANNEL(0),
+	MCP41010_CHANNEL(1),
+};
+
+static int mcp41010_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct mcp41010_data *data = iio_priv(indio_dev);
+	int channel = chan->channel;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*val = data->value[channel];
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		*val = 1000 * data->cfg->kohms;
+		*val2 = MCP41010_WIPER_MAX;
+		return IIO_VAL_FRACTIONAL;
+	}
+
+	return -EINVAL;
+}
+
+static int mcp41010_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long mask)
+{
+	int err;
+	struct mcp41010_data *data = iio_priv(indio_dev);
+	int channel = chan->channel;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (val > MCP41010_WIPER_MAX || val < 0)
+			return -EINVAL;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	mutex_lock(&data->lock);
+
+	data->buf[0] = MCP41010_WIPER_ENABLE << channel;
+	data->buf[0] |= MCP41010_WRITE;
+	data->buf[1] = val & 0xff;
+
+	err = spi_write(data->spi, data->buf, 2);
+	if (!err)
+		data->value[channel] = val;
+
+	mutex_unlock(&data->lock);
+
+	return err;
+}
+
+static const struct iio_info mcp41010_info = {
+	.read_raw = mcp41010_read_raw,
+	.write_raw = mcp41010_write_raw,
+};
+
+static int mcp41010_probe(struct spi_device *spi)
+{
+	int err;
+	struct device *dev = &spi->dev;
+	unsigned long devid = spi_get_device_id(spi)->driver_data;
+	struct mcp41010_data *data;
+	struct iio_dev *indio_dev;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	spi_set_drvdata(spi, indio_dev);
+	data->spi = spi;
+	data->cfg = &mcp41010_cfg[devid];
+
+	mutex_init(&data->lock);
+
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &mcp41010_info;
+	indio_dev->channels = mcp41010_channels;
+	indio_dev->num_channels = data->cfg->wipers;
+	indio_dev->name = spi_get_device_id(spi)->name;
+
+	err = devm_iio_device_register(dev, indio_dev);
+	if (err) {
+		dev_info(&spi->dev, "Unable to register %s\n", indio_dev->name);
+		return err;
+	}
+
+	return 0;
+}
+
+#if defined(CONFIG_OF)
+static const struct of_device_id mcp41010_dt_ids[] = {
+	{ .compatible = "microchip,mcp41010",
+		.data = &mcp41010_cfg[MCP41010] },
+	{ .compatible = "microchip,mcp41050",
+		.data = &mcp41010_cfg[MCP41050] },
+	{ .compatible = "microchip,mcp41100",
+		.data = &mcp41010_cfg[MCP41100] },
+	{ .compatible = "microchip,mcp42010",
+		.data = &mcp41010_cfg[MCP42010] },
+	{ .compatible = "microchip,mcp42050",
+		.data = &mcp41010_cfg[MCP42050] },
+	{ .compatible = "microchip,mcp42100",
+		.data = &mcp41010_cfg[MCP42100] },
+	{}
+};
+MODULE_DEVICE_TABLE(of, mcp41010_dt_ids);
+#endif /* CONFIG_OF */
+
+static const struct spi_device_id mcp41010_id[] = {
+	{ "mcp41010", MCP41010 },
+	{ "mcp41050", MCP41050 },
+	{ "mcp41100", MCP41100 },
+	{ "mcp42010", MCP42010 },
+	{ "mcp42050", MCP42050 },
+	{ "mcp42100", MCP42100 },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, mcp41010_id);
+
+static struct spi_driver mcp41010_driver = {
+	.driver = {
+		.name	= "mcp41010",
+		.of_match_table = of_match_ptr(mcp41010_dt_ids),
+	},
+	.probe		= mcp41010_probe,
+	.id_table	= mcp41010_id,
+};
+
+module_spi_driver(mcp41010_driver);
+
+MODULE_AUTHOR("Chris Coffey <cmc@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("MCP41010 digital potentiometer");
+MODULE_LICENSE("GPL v2");
-- 
2.11.0




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