267 lines
6.3 KiB
C
267 lines
6.3 KiB
C
/*
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* IIO DAC emulation driver using a digital potentiometer
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*
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* Copyright (C) 2016 Axentia Technologies AB
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*
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* Author: Peter Rosin <peda@axentia.se>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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/*
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* It is assumed that the dpot is used as a voltage divider between the
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* current dpot wiper setting and the maximum resistance of the dpot. The
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* divided voltage is provided by a vref regulator.
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*
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* .------.
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* .-----------. | |
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* | vref |--' .---.
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* | regulator |--. | |
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* '-----------' | | d |
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* | | p |
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* | | o | wiper
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* | | t |<---------+
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* | | |
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* | '---' dac output voltage
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* | |
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* '------+------------+
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*/
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#include <linux/err.h>
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#include <linux/iio/consumer.h>
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#include <linux/iio/iio.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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#include <linux/regulator/consumer.h>
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struct dpot_dac {
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struct regulator *vref;
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struct iio_channel *dpot;
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u32 max_ohms;
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};
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static const struct iio_chan_spec dpot_dac_iio_channel = {
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.type = IIO_VOLTAGE,
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.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)
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| BIT(IIO_CHAN_INFO_SCALE),
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.info_mask_separate_available = BIT(IIO_CHAN_INFO_RAW),
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.output = 1,
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.indexed = 1,
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};
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static int dpot_dac_read_raw(struct iio_dev *indio_dev,
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struct iio_chan_spec const *chan,
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int *val, int *val2, long mask)
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{
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struct dpot_dac *dac = iio_priv(indio_dev);
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int ret;
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unsigned long long tmp;
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switch (mask) {
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case IIO_CHAN_INFO_RAW:
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return iio_read_channel_raw(dac->dpot, val);
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case IIO_CHAN_INFO_SCALE:
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ret = iio_read_channel_scale(dac->dpot, val, val2);
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switch (ret) {
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case IIO_VAL_FRACTIONAL_LOG2:
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tmp = *val * 1000000000LL;
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do_div(tmp, dac->max_ohms);
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tmp *= regulator_get_voltage(dac->vref) / 1000;
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do_div(tmp, 1000000000LL);
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*val = tmp;
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return ret;
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case IIO_VAL_INT:
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/*
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* Convert integer scale to fractional scale by
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* setting the denominator (val2) to one...
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*/
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*val2 = 1;
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ret = IIO_VAL_FRACTIONAL;
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/* ...and fall through. */
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case IIO_VAL_FRACTIONAL:
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*val *= regulator_get_voltage(dac->vref) / 1000;
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*val2 *= dac->max_ohms;
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break;
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}
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return ret;
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}
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return -EINVAL;
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}
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static int dpot_dac_read_avail(struct iio_dev *indio_dev,
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struct iio_chan_spec const *chan,
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const int **vals, int *type, int *length,
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long mask)
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{
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struct dpot_dac *dac = iio_priv(indio_dev);
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switch (mask) {
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case IIO_CHAN_INFO_RAW:
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*type = IIO_VAL_INT;
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return iio_read_avail_channel_raw(dac->dpot, vals, length);
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}
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return -EINVAL;
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}
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static int dpot_dac_write_raw(struct iio_dev *indio_dev,
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struct iio_chan_spec const *chan,
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int val, int val2, long mask)
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{
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struct dpot_dac *dac = iio_priv(indio_dev);
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switch (mask) {
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case IIO_CHAN_INFO_RAW:
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return iio_write_channel_raw(dac->dpot, val);
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}
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return -EINVAL;
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}
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static const struct iio_info dpot_dac_info = {
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.read_raw = dpot_dac_read_raw,
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.read_avail = dpot_dac_read_avail,
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.write_raw = dpot_dac_write_raw,
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.driver_module = THIS_MODULE,
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};
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static int dpot_dac_channel_max_ohms(struct iio_dev *indio_dev)
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{
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struct device *dev = &indio_dev->dev;
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struct dpot_dac *dac = iio_priv(indio_dev);
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unsigned long long tmp;
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int ret;
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int val;
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int val2;
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int max;
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ret = iio_read_max_channel_raw(dac->dpot, &max);
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if (ret < 0) {
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dev_err(dev, "dpot does not indicate its raw maximum value\n");
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return ret;
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}
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switch (iio_read_channel_scale(dac->dpot, &val, &val2)) {
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case IIO_VAL_INT:
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return max * val;
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case IIO_VAL_FRACTIONAL:
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tmp = (unsigned long long)max * val;
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do_div(tmp, val2);
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return tmp;
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case IIO_VAL_FRACTIONAL_LOG2:
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tmp = val * 1000000000LL * max >> val2;
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do_div(tmp, 1000000000LL);
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return tmp;
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default:
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dev_err(dev, "dpot has a scale that is too weird\n");
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}
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return -EINVAL;
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}
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static int dpot_dac_probe(struct platform_device *pdev)
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{
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struct device *dev = &pdev->dev;
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struct iio_dev *indio_dev;
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struct dpot_dac *dac;
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enum iio_chan_type type;
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int ret;
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indio_dev = devm_iio_device_alloc(dev, sizeof(*dac));
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if (!indio_dev)
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return -ENOMEM;
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platform_set_drvdata(pdev, indio_dev);
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dac = iio_priv(indio_dev);
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indio_dev->name = dev_name(dev);
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indio_dev->dev.parent = dev;
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indio_dev->info = &dpot_dac_info;
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indio_dev->modes = INDIO_DIRECT_MODE;
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indio_dev->channels = &dpot_dac_iio_channel;
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indio_dev->num_channels = 1;
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dac->vref = devm_regulator_get(dev, "vref");
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if (IS_ERR(dac->vref)) {
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if (PTR_ERR(dac->vref) != -EPROBE_DEFER)
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dev_err(&pdev->dev, "failed to get vref regulator\n");
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return PTR_ERR(dac->vref);
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}
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dac->dpot = devm_iio_channel_get(dev, "dpot");
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if (IS_ERR(dac->dpot)) {
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if (PTR_ERR(dac->dpot) != -EPROBE_DEFER)
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dev_err(dev, "failed to get dpot input channel\n");
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return PTR_ERR(dac->dpot);
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}
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ret = iio_get_channel_type(dac->dpot, &type);
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if (ret < 0)
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return ret;
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if (type != IIO_RESISTANCE) {
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dev_err(dev, "dpot is of the wrong type\n");
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return -EINVAL;
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}
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ret = dpot_dac_channel_max_ohms(indio_dev);
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if (ret < 0)
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return ret;
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dac->max_ohms = ret;
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ret = regulator_enable(dac->vref);
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if (ret) {
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dev_err(dev, "failed to enable the vref regulator\n");
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return ret;
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}
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ret = iio_device_register(indio_dev);
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if (ret) {
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dev_err(dev, "failed to register iio device\n");
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goto disable_reg;
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}
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return 0;
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disable_reg:
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regulator_disable(dac->vref);
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return ret;
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}
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static int dpot_dac_remove(struct platform_device *pdev)
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{
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struct iio_dev *indio_dev = platform_get_drvdata(pdev);
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struct dpot_dac *dac = iio_priv(indio_dev);
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iio_device_unregister(indio_dev);
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regulator_disable(dac->vref);
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return 0;
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}
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static const struct of_device_id dpot_dac_match[] = {
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{ .compatible = "dpot-dac" },
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{ /* sentinel */ }
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};
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MODULE_DEVICE_TABLE(of, dpot_dac_match);
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static struct platform_driver dpot_dac_driver = {
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.probe = dpot_dac_probe,
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.remove = dpot_dac_remove,
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.driver = {
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.name = "iio-dpot-dac",
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.of_match_table = dpot_dac_match,
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},
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};
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module_platform_driver(dpot_dac_driver);
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MODULE_DESCRIPTION("DAC emulation driver using a digital potentiometer");
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MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
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MODULE_LICENSE("GPL v2");
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