[PATCH v5] iio: max5487: Add support for Maxim digital potentiometers

From: Cristina Moraru
Date: Thu May 19 2016 - 01:56:12 EST

Add implementation for Maxim MAX5487, MAX5488, MAX5489
digital potentiometers.

Datasheet:
http://datasheets.maximintegrated.com/en/ds/MAX5487-MAX5489.pdf

Signed-off-by: Cristina Moraru <cristina.moraru09@xxxxxxxxx>
CC: Daniel Baluta <daniel.baluta@xxxxxxxxx>
---
Changes since v4:
Add year for copyright
Changes since v3:
Fix size issue in max5487_write_cmd
Fix typo
Changes since v2:
Change switch statement in max5487_write_raw
to if statement for consistency
Add blank line before return statement
Eliminate regmap support and use spi_write
Use iio_device_register instead of devm_ version
Changes since v1:
Fix spacing
Eliminate max5487_cfg struct
Add kohms as driver data

drivers/iio/potentiometer/Kconfig | 11 +++
drivers/iio/potentiometer/Makefile | 1 +
drivers/iio/potentiometer/max5487.c | 161 ++++++++++++++++++++++++++++++++++++
3 files changed, 173 insertions(+)
create mode 100644 drivers/iio/potentiometer/max5487.c

diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
index 6acb238..0941c8d4 100644
--- a/drivers/iio/potentiometer/Kconfig
+++ b/drivers/iio/potentiometer/Kconfig
@@ -15,6 +15,17 @@ config DS1803
To compile this driver as a module, choose M here: the
module will be called ds1803.

+config MAX5487
+ tristate "Maxim MAX5487/MAX5488/MAX5489 Digital Potentiometer driver"
+ depends on SPI
+ help
+ Say yes here to build support for the Maxim
+ MAX5487, MAX5488, MAX5489 digital potentiometer
+ chips.
+
+ To compile this driver as a module, choose M here: the
+ module will be called max5487.
+
config MCP4131
tristate "Microchip MCP413X/414X/415X/416X/423X/424X/425X/426X Digital Potentiometer driver"
depends on SPI
diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
index 6007faa..8adb58f 100644
--- a/drivers/iio/potentiometer/Makefile
+++ b/drivers/iio/potentiometer/Makefile
@@ -4,6 +4,7 @@

# When adding new entries keep the list in alphabetical order
obj-$(CONFIG_DS1803) += ds1803.o
+obj-$(CONFIG_MAX5487) += max5487.o
obj-$(CONFIG_MCP4131) += mcp4131.o
obj-$(CONFIG_MCP4531) += mcp4531.o
obj-$(CONFIG_TPL0102) += tpl0102.o
diff --git a/drivers/iio/potentiometer/max5487.c b/drivers/iio/potentiometer/max5487.c
new file mode 100644
index 0000000..6c50939
--- /dev/null
+++ b/drivers/iio/potentiometer/max5487.c
@@ -0,0 +1,161 @@
+/*
+ * max5487.c - Support for MAX5487, MAX5488, MAX5489 digital potentiometers
+ *
+ * Copyright (C) 2016 Cristina-Gabriela Moraru <cristina.moraru09@xxxxxxxxx>
+ *
+ * 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/module.h>
+#include <linux/spi/spi.h>
+#include <linux/acpi.h>
+
+#include <linux/iio/sysfs.h>
+#include <linux/iio/iio.h>
+
+#define MAX5487_WRITE_WIPER_A (0x01 << 8)
+#define MAX5487_WRITE_WIPER_B (0x02 << 8)
+
+/* copy both wiper regs to NV regs */
+#define MAX5487_COPY_AB_TO_NV (0x23 << 8)
+/* copy both NV regs to wiper regs */
+#define MAX5487_COPY_NV_TO_AB (0x33 << 8)
+
+#define MAX5487_MAX_POS 255
+
+struct max5487_data {
+ struct spi_device *spi;
+ int kohms;
+};
+
+#define MAX5487_CHANNEL(ch, addr) { \
+ .type = IIO_RESISTANCE, \
+ .indexed = 1, \
+ .output = 1, \
+ .channel = ch, \
+ .address = addr, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+}
+
+static const struct iio_chan_spec max5487_channels[] = {
+ MAX5487_CHANNEL(0, MAX5487_WRITE_WIPER_A),
+ MAX5487_CHANNEL(1, MAX5487_WRITE_WIPER_B),
+};
+
+static int max5487_write_cmd(struct spi_device *spi, u16 cmd)
+{
+ return spi_write(spi, (const void *) &cmd, sizeof(u16));
+}
+
+static int max5487_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct max5487_data *data = iio_priv(indio_dev);
+
+ if (mask != IIO_CHAN_INFO_SCALE)
+ return -EINVAL;
+
+ *val = 1000 * data->kohms;
+ *val2 = MAX5487_MAX_POS;
+
+ return IIO_VAL_FRACTIONAL;
+}
+
+static int max5487_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct max5487_data *data = iio_priv(indio_dev);
+
+ if (mask != IIO_CHAN_INFO_RAW)
+ return -EINVAL;
+
+ if (val < 0 || val > MAX5487_MAX_POS)
+ return -EINVAL;
+
+ return max5487_write_cmd(data->spi, chan->address | val);
+}
+
+static const struct iio_info max5487_info = {
+ .read_raw = max5487_read_raw,
+ .write_raw = max5487_write_raw,
+ .driver_module = THIS_MODULE,
+};
+
+static int max5487_spi_probe(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev;
+ struct max5487_data *data;
+ const struct spi_device_id *id = spi_get_device_id(spi);
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ dev_set_drvdata(&spi->dev, indio_dev);
+ data = iio_priv(indio_dev);
+
+ data->spi = spi;
+ data->kohms = id->driver_data;
+
+ indio_dev->info = &max5487_info;
+ indio_dev->name = id->name;
+ indio_dev->dev.parent = &spi->dev;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = max5487_channels;
+ indio_dev->num_channels = ARRAY_SIZE(max5487_channels);
+
+ /* restore both wiper regs from NV regs */
+ ret = max5487_write_cmd(data->spi, MAX5487_COPY_NV_TO_AB);
+ if (ret < 0)
+ return ret;
+
+ return iio_device_register(indio_dev);
+}
+
+static int max5487_spi_remove(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
+
+ iio_device_unregister(indio_dev);
+
+ /* save both wiper regs to NV regs */
+ return max5487_write_cmd(spi, MAX5487_COPY_AB_TO_NV);
+}
+
+static const struct spi_device_id max5487_id[] = {
+ { "MAX5487", 10 },
+ { "MAX5488", 50 },
+ { "MAX5489", 100 },
+ { }
+};
+MODULE_DEVICE_TABLE(spi, max5487_id);
+
+static const struct acpi_device_id max5487_acpi_match[] = {
+ { "MAX5487", 10 },
+ { "MAX5488", 50 },
+ { "MAX5489", 100 },
+ { },
+};
+MODULE_DEVICE_TABLE(acpi, max5487_acpi_match);
+
+static struct spi_driver max5487_driver = {
+ .driver = {
+ .name = "max5487",
+ .owner = THIS_MODULE,
+ .acpi_match_table = ACPI_PTR(max5487_acpi_match),
+ },
+ .id_table = max5487_id,
+ .probe = max5487_spi_probe,
+ .remove = max5487_spi_remove
+};
+module_spi_driver(max5487_driver);
+
+MODULE_AUTHOR("Cristina-Gabriela Moraru <cristina.moraru09@xxxxxxxxx>");
+MODULE_DESCRIPTION("max5487 SPI driver");
+MODULE_LICENSE("GPL v2");
--
1.9.1