--- /dev/null
+/*
+ * IIO DAC emulation driver using a digital potentiometer
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * Author: Peter Rosin <peda@axentia.se>
+ *
+ * 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.
+ */
+
+/*
+ * It is assumed that the dpot is used as a voltage divider between the
+ * current dpot wiper setting and the maximum resistance of the dpot. The
+ * divided voltage is provided by a vref regulator.
+ *
+ * .------.
+ * .-----------. | |
+ * | vref |--' .---.
+ * | regulator |--. | |
+ * '-----------' | | d |
+ * | | p |
+ * | | o | wiper
+ * | | t |<---------+
+ * | | |
+ * | '---' dac output voltage
+ * | |
+ * '------+------------+
+ */
+
+#include <linux/err.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+
+struct dpot_dac {
+ struct regulator *vref;
+ struct iio_channel *dpot;
+ u32 max_ohms;
+};
+
+static const struct iio_chan_spec dpot_dac_iio_channel = {
+ .type = IIO_VOLTAGE,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW)
+ | BIT(IIO_CHAN_INFO_SCALE),
+ .info_mask_separate_available = BIT(IIO_CHAN_INFO_RAW),
+ .output = 1,
+ .indexed = 1,
+};
+
+static int dpot_dac_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct dpot_dac *dac = iio_priv(indio_dev);
+ int ret;
+ unsigned long long tmp;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ return iio_read_channel_raw(dac->dpot, val);
+
+ case IIO_CHAN_INFO_SCALE:
+ ret = iio_read_channel_scale(dac->dpot, val, val2);
+ switch (ret) {
+ case IIO_VAL_FRACTIONAL_LOG2:
+ tmp = *val * 1000000000LL;
+ do_div(tmp, dac->max_ohms);
+ tmp *= regulator_get_voltage(dac->vref) / 1000;
+ do_div(tmp, 1000000000LL);
+ *val = tmp;
+ return ret;
+ case IIO_VAL_INT:
+ /*
+ * Convert integer scale to fractional scale by
+ * setting the denominator (val2) to one...
+ */
+ *val2 = 1;
+ ret = IIO_VAL_FRACTIONAL;
+ /* ...and fall through. */
+ case IIO_VAL_FRACTIONAL:
+ *val *= regulator_get_voltage(dac->vref) / 1000;
+ *val2 *= dac->max_ohms;
+ break;
+ }
+
+ return ret;
+ }
+
+ return -EINVAL;
+}
+
+static int dpot_dac_read_avail(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ const int **vals, int *type, int *length,
+ long mask)
+{
+ struct dpot_dac *dac = iio_priv(indio_dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ *type = IIO_VAL_INT;
+ return iio_read_avail_channel_raw(dac->dpot, vals, length);
+ }
+
+ return -EINVAL;
+}
+
+static int dpot_dac_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct dpot_dac *dac = iio_priv(indio_dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ return iio_write_channel_raw(dac->dpot, val);
+ }
+
+ return -EINVAL;
+}
+
+static const struct iio_info dpot_dac_info = {
+ .read_raw = dpot_dac_read_raw,
+ .read_avail = dpot_dac_read_avail,
+ .write_raw = dpot_dac_write_raw,
+ .driver_module = THIS_MODULE,
+};
+
+static int dpot_dac_channel_max_ohms(struct iio_dev *indio_dev)
+{
+ struct device *dev = &indio_dev->dev;
+ struct dpot_dac *dac = iio_priv(indio_dev);
+ unsigned long long tmp;
+ int ret;
+ int val;
+ int val2;
+ int max;
+
+ ret = iio_read_max_channel_raw(dac->dpot, &max);
+ if (ret < 0) {
+ dev_err(dev, "dpot does not indicate its raw maximum value\n");
+ return ret;
+ }
+
+ switch (iio_read_channel_scale(dac->dpot, &val, &val2)) {
+ case IIO_VAL_INT:
+ return max * val;
+ case IIO_VAL_FRACTIONAL:
+ tmp = (unsigned long long)max * val;
+ do_div(tmp, val2);
+ return tmp;
+ case IIO_VAL_FRACTIONAL_LOG2:
+ tmp = val * 1000000000LL * max >> val2;
+ do_div(tmp, 1000000000LL);
+ return tmp;
+ default:
+ dev_err(dev, "dpot has a scale that is too weird\n");
+ }
+
+ return -EINVAL;
+}
+
+static int dpot_dac_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct iio_dev *indio_dev;
+ struct dpot_dac *dac;
+ enum iio_chan_type type;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(dev, sizeof(*dac));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ platform_set_drvdata(pdev, indio_dev);
+ dac = iio_priv(indio_dev);
+
+ indio_dev->name = dev_name(dev);
+ indio_dev->dev.parent = dev;
+ indio_dev->info = &dpot_dac_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = &dpot_dac_iio_channel;
+ indio_dev->num_channels = 1;
+
+ dac->vref = devm_regulator_get(dev, "vref");
+ if (IS_ERR(dac->vref)) {
+ if (PTR_ERR(dac->vref) != -EPROBE_DEFER)
+ dev_err(&pdev->dev, "failed to get vref regulator\n");
+ return PTR_ERR(dac->vref);
+ }
+
+ dac->dpot = devm_iio_channel_get(dev, "dpot");
+ if (IS_ERR(dac->dpot)) {
+ if (PTR_ERR(dac->dpot) != -EPROBE_DEFER)
+ dev_err(dev, "failed to get dpot input channel\n");
+ return PTR_ERR(dac->dpot);
+ }
+
+ ret = iio_get_channel_type(dac->dpot, &type);
+ if (ret < 0)
+ return ret;
+
+ if (type != IIO_RESISTANCE) {
+ dev_err(dev, "dpot is of the wrong type\n");
+ return -EINVAL;
+ }
+
+ ret = dpot_dac_channel_max_ohms(indio_dev);
+ if (ret < 0)
+ return ret;
+ dac->max_ohms = ret;
+
+ ret = regulator_enable(dac->vref);
+ if (ret) {
+ dev_err(dev, "failed to enable the vref regulator\n");
+ return ret;
+ }
+
+ ret = iio_device_register(indio_dev);
+ if (ret) {
+ dev_err(dev, "failed to register iio device\n");
+ goto disable_reg;
+ }
+
+ return 0;
+
+disable_reg:
+ regulator_disable(dac->vref);
+ return ret;
+}
+
+static int dpot_dac_remove(struct platform_device *pdev)
+{
+ struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+ struct dpot_dac *dac = iio_priv(indio_dev);
+
+ iio_device_unregister(indio_dev);
+ regulator_disable(dac->vref);
+
+ return 0;
+}
+
+static const struct of_device_id dpot_dac_match[] = {
+ { .compatible = "dpot-dac" },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, dpot_dac_match);
+
+static struct platform_driver dpot_dac_driver = {
+ .probe = dpot_dac_probe,
+ .remove = dpot_dac_remove,
+ .driver = {
+ .name = "iio-dpot-dac",
+ .of_match_table = dpot_dac_match,
+ },
+};
+module_platform_driver(dpot_dac_driver);
+
+MODULE_DESCRIPTION("DAC emulation driver using a digital potentiometer");
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
+MODULE_LICENSE("GPL v2");
projects / platform / kernel / linux-rpi3.git / commitdiff