// SPDX-License-Identifier: GPL-2.0 /* * IIO DAC emulation driver using a digital potentiometer * * Copyright (C) 2016 Axentia Technologies AB * * Author: Peter Rosin */ /* * 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. Say it again for GCC. */ fallthrough; 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, }; 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->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)) return dev_err_probe(&pdev->dev, PTR_ERR(dac->vref), "failed to get vref regulator\n"); dac->dpot = devm_iio_channel_get(dev, "dpot"); if (IS_ERR(dac->dpot)) return dev_err_probe(&pdev->dev, PTR_ERR(dac->dpot), "failed to get dpot input channel\n"); 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 void 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); } 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");