[PATCH v3 0/2] Add support for Microchip MCP41xxx/42xxx potentiometers

[PATCH v3 0/2] Add support for Microchip MCP41xxx/42xxx potentiometers

[Chris Coffey]

Hello all,

This patch series adds device-tree documentation and driver support
for the Microchip MCP41xxx/42xxx family of digital potentiometers.

Changes in v3:
 - Get device names from mcp41010_cfg struct instead of spi device as
   suggested by Jonathan Cameron.
 - Refactor code structure in mcp41010_write_raw() as recommended by
   Jonathan Cameron.
 - Only call spi_get_device_id() when necessary to load config as
   suggested by Slawomir Stepien.
 - In mcp41010_probe(), return err to make static checkers happy as
   recommended by Jonathan Cameron.
 - Edit mcp41010_match struct members to fit on one line as suggested
   by Slawomir Stepien.
 - In device tree binding documentation, add company name to example
   as pointed out by Slawomir Stepien.
 - In device tree binding documentation, remove mcp41010 prefix from
   example as suggested by Jonathan Cameron.

Changes in v2:
 - Move device tree binding documentation to separate commit as
   pointed out by Himanshu Jha.
 - Remove explicit '= 0' initialization in mcp41010_type enum as
   recommended by Himanshu Jha.
 - Change MCP41010_WRITE from (0x01 << 4) to BIT(4) as recommended by
   Himanshu Jha.
 - Use of_device_get_match_data() to load configuration as 
   recommended by Peter Rosin. 
 - Rename MCP41010_WIPER_ENABLE to MCP41010_WIPER_CHANNEL as 
   suggested by Peter Rosin.
 - Remove CONFIG_OF build protections as recommended by Jonathan
   Cameron.
 - Remove of_match_ptr wrapper from mcp41010_driver struct as 
   recommended by Jonathan Cameron.
 - Remove blank line in mcp41010.c intro as recommended by Jonathan
   Cameron.

Chris Coffey (2):
  dt-bindings: iio: potentiometer: Add Microchip MCP41xxx/42xxx
  iio: potentiometer: Add driver for Microchip MCP41xxx/42xxx

 .../bindings/iio/potentiometer/mcp41010.txt        |  29 +++
 drivers/iio/potentiometer/Kconfig                  |  12 ++
 drivers/iio/potentiometer/Makefile                 |   1 +
 drivers/iio/potentiometer/mcp41010.c               | 204 +++++++++++++++++++++
 4 files changed, 246 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt
 create mode 100644 drivers/iio/potentiometer/mcp41010.c

-- 
2.11.0

[PATCH v3 1/2] dt-bindings: iio: potentiometer: Add Microchip MCP41xxx/42xxx

[Chris Coffey]

This patch adds device tree documentation for the Microchip
MCP41xxx/42xxx family of digital potentiometers.

Signed-off-by: Chris Coffey <cmc@babblebit.net>
---
 .../bindings/iio/potentiometer/mcp41010.txt        | 29 ++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt

diff --git a/Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt b/Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt
new file mode 100644
index 0000000000..7dcf2071b7
--- /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:
+potentiometer@0 {
+	compatible = "microchip,mcp41010";
+	reg = <0>;
+	spi-max-frequency = <500000>;
+};
-- 
2.11.0

[PATCH v3 2/2] iio: potentiometer: Add driver for Microchip MCP41xxx/42xxx

[Chris Coffey]

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@babblebit.net>
---
 drivers/iio/potentiometer/Kconfig    |  12 +++
 drivers/iio/potentiometer/Makefile   |   1 +
 drivers/iio/potentiometer/mcp41010.c | 204 +++++++++++++++++++++++++++++++++++
 3 files changed, 217 insertions(+)
 create mode 100644 drivers/iio/potentiometer/mcp41010.c

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..4a91066cb1
--- /dev/null
+++ b/drivers/iio/potentiometer/mcp41010.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Industrial I/O driver for Microchip digital potentiometers
+ *
+ * Copyright (c) 2018 Chris Coffey <cmc@babblebit.net>
+ * 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/of_device.h>
+#include <linux/spi/spi.h>
+
+#define MCP41010_MAX_WIPERS	2
+#define MCP41010_WRITE		BIT(4)
+#define MCP41010_WIPER_MAX	255
+#define MCP41010_WIPER_CHANNEL	BIT(0)
+
+struct mcp41010_cfg {
+	char name[16];
+	int wipers;
+	int kohms;
+};
+
+enum mcp41010_type {
+	MCP41010,
+	MCP41050,
+	MCP41100,
+	MCP42010,
+	MCP42050,
+	MCP42100,
+};
+
+static const struct mcp41010_cfg mcp41010_cfg[] = {
+	[MCP41010] = { .name = "mcp41010", .wipers = 1, .kohms =  10, },
+	[MCP41050] = { .name = "mcp41050", .wipers = 1, .kohms =  50, },
+	[MCP41100] = { .name = "mcp41100", .wipers = 1, .kohms = 100, },
+	[MCP42010] = { .name = "mcp42010", .wipers = 2, .kohms =  10, },
+	[MCP42050] = { .name = "mcp42050", .wipers = 2, .kohms =  50, },
+	[MCP42100] = { .name = "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;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	if (val > MCP41010_WIPER_MAX || val < 0)
+		return -EINVAL;
+
+	mutex_lock(&data->lock);
+
+	data->buf[0] = MCP41010_WIPER_CHANNEL << 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;
+	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 = of_device_get_match_data(&spi->dev);
+	if (!data->cfg)
+		data->cfg = &mcp41010_cfg[spi_get_device_id(spi)->driver_data];
+
+	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 = data->cfg->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;
+}
+
+static const struct of_device_id mcp41010_match[] = {
+	{ .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_match);
+
+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 = mcp41010_match,
+	},
+	.probe		= mcp41010_probe,
+	.id_table	= mcp41010_id,
+};
+
+module_spi_driver(mcp41010_driver);
+
+MODULE_AUTHOR("Chris Coffey <cmc@babblebit.net>");
+MODULE_DESCRIPTION("MCP41010 digital potentiometer");
+MODULE_LICENSE("GPL v2");
-- 
2.11.0

Re: [PATCH v3 1/2] dt-bindings: iio: potentiometer: Add Microchip MCP41xxx/42xxx

[Jonathan Cameron]

On Tue, 20 Nov 2018 14:17:12 +0000
Chris Coffey <cmc@babblebit.net> wrote:

> This patch adds device tree documentation for the Microchip
> MCP41xxx/42xxx family of digital potentiometers.
> 
> Signed-off-by: Chris Coffey <cmc@babblebit.net>
> ---
>  .../bindings/iio/potentiometer/mcp41010.txt        | 29 ++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt
> 
> diff --git a/Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt b/Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt
> new file mode 100644
> index 0000000000..7dcf2071b7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/potentiometer/mcp41010.txt
> @@ -0,0 +1,29 @@
> +* Microchip MCP41010/41050/41100/42010/42050/42100 Digital Potentiometer
> +  driver
I'll channel my inner Rob ;)  Bindings are for devices, not drivers
(basically don't mention driver anywhere)

It's trivial (and common) so I just tidied it up whilst applying.

Applied to the togreg branch of iio.git and pushed out as testing for
the autobuilders to play with it.

Thanks,

Jonathan

> +
> +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:
> +potentiometer@0 {
> +	compatible = "microchip,mcp41010";
> +	reg = <0>;
> +	spi-max-frequency = <500000>;
> +};