iio: dpot-dac: DAC driver based on a digital potentiometer (7fde1484) · Commits · e / devices / android_kernel_fairphone_FP4

Documentation/ABI/testing/sysfs-bus-iio-dac-dpot-dac

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			What: /sys/bus/iio/devices/iio:deviceX/out_voltageY_raw_available
			Date: October 2016
			KernelVersion: 4.9
			Contact: Peter Rosin <peda@axentia.se>
			Description:
			The range of available values represented as the minimum value,
			the step and the maximum value, all enclosed in square brackets.
			Example: [0 1 256]

MAINTAINERS

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	@@ -6123,7 +6123,9 @@ IIO DIGITAL POTENTIOMETER DAC
	M: Peter Rosin <peda@axentia.se>		M: Peter Rosin <peda@axentia.se>
	L: linux-iio@vger.kernel.org		L: linux-iio@vger.kernel.org
	S: Maintained		S: Maintained
			F: Documentation/ABI/testing/sysfs-bus-iio-dac-dpot-dac
	F: Documentation/devicetree/bindings/iio/dac/dpot-dac.txt		F: Documentation/devicetree/bindings/iio/dac/dpot-dac.txt
			F: drivers/iio/dac/dpot-dac.c

	IIO SUBSYSTEM AND DRIVERS		IIO SUBSYSTEM AND DRIVERS
	M: Jonathan Cameron <jic23@kernel.org>		M: Jonathan Cameron <jic23@kernel.org>

drivers/iio/dac/Kconfig

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	@@ -200,6 +200,16 @@ config AD8801
	To compile this driver as a module choose M here: the module will be called		To compile this driver as a module choose M here: the module will be called
	ad8801.		ad8801.

			config DPOT_DAC
			tristate "DAC emulation using a DPOT"
			depends on OF
			help
			Say yes here to build support for DAC emulation using a digital
			potentiometer.

			To compile this driver as a module, choose M here: the module will be
			called dpot-dac.

	config LPC18XX_DAC		config LPC18XX_DAC
	tristate "NXP LPC18xx DAC driver"		tristate "NXP LPC18xx DAC driver"
	depends on ARCH_LPC18XX \|\| COMPILE_TEST		depends on ARCH_LPC18XX \|\| COMPILE_TEST

drivers/iio/dac/Makefile

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	@@ -22,6 +22,7 @@ obj-$(CONFIG_AD5686) += ad5686.o
	obj-$(CONFIG_AD7303) += ad7303.o		obj-$(CONFIG_AD7303) += ad7303.o
	obj-$(CONFIG_AD8801) += ad8801.o		obj-$(CONFIG_AD8801) += ad8801.o
	obj-$(CONFIG_CIO_DAC) += cio-dac.o		obj-$(CONFIG_CIO_DAC) += cio-dac.o
			obj-$(CONFIG_DPOT_DAC) += dpot-dac.o
	obj-$(CONFIG_LPC18XX_DAC) += lpc18xx_dac.o		obj-$(CONFIG_LPC18XX_DAC) += lpc18xx_dac.o
	obj-$(CONFIG_M62332) += m62332.o		obj-$(CONFIG_M62332) += m62332.o
	obj-$(CONFIG_MAX517) += max517.o		obj-$(CONFIG_MAX517) += max517.o

drivers/iio/dac/dpot-dac.c

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			/*
			* 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");