From 7fde1484af21f9668e9575bd8a119ebc4fe6fe42 Mon Sep 17 00:00:00 2001 From: Peter Rosin Date: Tue, 8 Nov 2016 12:58:56 +0100 Subject: iio: dpot-dac: DAC driver based on a digital potentiometer 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 | | '------+------------+ Signed-off-by: Peter Rosin Signed-off-by: Jonathan Cameron --- drivers/iio/dac/dpot-dac.c | 266 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 266 insertions(+) create mode 100644 drivers/iio/dac/dpot-dac.c (limited to 'drivers/iio/dac/dpot-dac.c') diff --git a/drivers/iio/dac/dpot-dac.c b/drivers/iio/dac/dpot-dac.c new file mode 100644 index 000000000000..960a2b430480 --- /dev/null +++ b/drivers/iio/dac/dpot-dac.c @@ -0,0 +1,266 @@ +/* + * IIO DAC emulation driver using a digital potentiometer + * + * Copyright (C) 2016 Axentia Technologies AB + * + * Author: Peter Rosin + * + * 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 +#include +#include +#include +#include +#include +#include + +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 "); +MODULE_LICENSE("GPL v2"); -- cgit v1.2.1