--- /dev/null
+/*
+ * Maxim Integrated MAX5481-MAX5484 digital potentiometer driver
+ * Copyright 2016 Rockwell Collins
+ *
+ * Datasheet:
+ * http://datasheets.maximintegrated.com/en/ds/MAX5481-MAX5484.pdf
+ *
+ * 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/acpi.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+
+/* write wiper reg */
+#define MAX5481_WRITE_WIPER (0 << 4)
+/* copy wiper reg to NV reg */
+#define MAX5481_COPY_AB_TO_NV (2 << 4)
+/* copy NV reg to wiper reg */
+#define MAX5481_COPY_NV_TO_AB (3 << 4)
+
+#define MAX5481_MAX_POS 1023
+
+enum max5481_variant {
+ max5481,
+ max5482,
+ max5483,
+ max5484,
+};
+
+struct max5481_cfg {
+ int kohms;
+};
+
+static const struct max5481_cfg max5481_cfg[] = {
+ [max5481] = { .kohms = 10, },
+ [max5482] = { .kohms = 50, },
+ [max5483] = { .kohms = 10, },
+ [max5484] = { .kohms = 50, },
+};
+
+struct max5481_data {
+ struct spi_device *spi;
+ const struct max5481_cfg *cfg;
+ u8 msg[3] ____cacheline_aligned;
+};
+
+#define MAX5481_CHANNEL { \
+ .type = IIO_RESISTANCE, \
+ .indexed = 1, \
+ .output = 1, \
+ .channel = 0, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+}
+
+static const struct iio_chan_spec max5481_channels[] = {
+ MAX5481_CHANNEL,
+};
+
+static int max5481_write_cmd(struct max5481_data *data, u8 cmd, u16 val)
+{
+ struct spi_device *spi = data->spi;
+
+ data->msg[0] = cmd;
+
+ switch (cmd) {
+ case MAX5481_WRITE_WIPER:
+ data->msg[1] = val >> 2;
+ data->msg[2] = (val & 0x3) << 6;
+ return spi_write(spi, data->msg, 3);
+
+ case MAX5481_COPY_AB_TO_NV:
+ case MAX5481_COPY_NV_TO_AB:
+ return spi_write(spi, data->msg, 1);
+
+ default:
+ return -EIO;
+ }
+}
+
+static int max5481_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct max5481_data *data = iio_priv(indio_dev);
+
+ if (mask != IIO_CHAN_INFO_SCALE)
+ return -EINVAL;
+
+ *val = 1000 * data->cfg->kohms;
+ *val2 = MAX5481_MAX_POS;
+
+ return IIO_VAL_FRACTIONAL;
+}
+
+static int max5481_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct max5481_data *data = iio_priv(indio_dev);
+
+ if (mask != IIO_CHAN_INFO_RAW)
+ return -EINVAL;
+
+ if (val < 0 || val > MAX5481_MAX_POS)
+ return -EINVAL;
+
+ return max5481_write_cmd(data, MAX5481_WRITE_WIPER, val);
+}
+
+static const struct iio_info max5481_info = {
+ .read_raw = max5481_read_raw,
+ .write_raw = max5481_write_raw,
+ .driver_module = THIS_MODULE,
+};
+
+#if defined(CONFIG_OF)
+static const struct of_device_id max5481_match[] = {
+ { .compatible = "maxim,max5481", .data = &max5481_cfg[max5481] },
+ { .compatible = "maxim,max5482", .data = &max5481_cfg[max5482] },
+ { .compatible = "maxim,max5483", .data = &max5481_cfg[max5483] },
+ { .compatible = "maxim,max5484", .data = &max5481_cfg[max5484] },
+ { }
+};
+MODULE_DEVICE_TABLE(of, max5481_match);
+#endif
+
+static int max5481_probe(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev;
+ struct max5481_data *data;
+ const struct spi_device_id *id = spi_get_device_id(spi);
+ const struct of_device_id *match;
+ 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;
+
+ match = of_match_device(of_match_ptr(max5481_match), &spi->dev);
+ if (match)
+ data->cfg = of_device_get_match_data(&spi->dev);
+ else
+ data->cfg = &max5481_cfg[id->driver_data];
+
+ indio_dev->name = id->name;
+ indio_dev->dev.parent = &spi->dev;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+
+ /* variant specific configuration */
+ indio_dev->info = &max5481_info;
+ indio_dev->channels = max5481_channels;
+ indio_dev->num_channels = ARRAY_SIZE(max5481_channels);
+
+ /* restore wiper from NV */
+ ret = max5481_write_cmd(data, MAX5481_COPY_NV_TO_AB, 0);
+ if (ret < 0)
+ return ret;
+
+ return iio_device_register(indio_dev);
+}
+
+static int max5481_remove(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
+ struct max5481_data *data = iio_priv(indio_dev);
+
+ iio_device_unregister(indio_dev);
+
+ /* save wiper reg to NV reg */
+ return max5481_write_cmd(data, MAX5481_COPY_AB_TO_NV, 0);
+}
+
+static const struct spi_device_id max5481_id_table[] = {
+ { "max5481", max5481 },
+ { "max5482", max5482 },
+ { "max5483", max5483 },
+ { "max5484", max5484 },
+ { }
+};
+MODULE_DEVICE_TABLE(spi, max5481_id_table);
+
+#if defined(CONFIG_ACPI)
+static const struct acpi_device_id max5481_acpi_match[] = {
+ { "max5481", max5481 },
+ { "max5482", max5482 },
+ { "max5483", max5483 },
+ { "max5484", max5484 },
+ { }
+};
+MODULE_DEVICE_TABLE(acpi, max5481_acpi_match);
+#endif
+
+static struct spi_driver max5481_driver = {
+ .driver = {
+ .name = "max5481",
+ .owner = THIS_MODULE,
+ .of_match_table = of_match_ptr(max5481_match),
+ .acpi_match_table = ACPI_PTR(max5481_acpi_match),
+ },
+ .probe = max5481_probe,
+ .remove = max5481_remove,
+ .id_table = max5481_id_table,
+};
+
+module_spi_driver(max5481_driver);
+
+MODULE_AUTHOR("Maury Anderson <maury.anderson@rockwellcollins.com>");
+MODULE_DESCRIPTION("max5481 SPI driver");
+MODULE_LICENSE("GPL v2");
projects / platform / kernel / linux-exynos.git / commitdiff