iio: adc: Add support for STM32 ADC

This patch adds support for STMicroelectronics STM32 MCU's analog to
digital converter.

Signed-off-by: Fabrice Gasnier <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/Kconfig

···
 	  This driver can also be built as a module.  If so, the module
 	  will be called stm32-adc-core.
 
+config STM32_ADC
+	tristate "STMicroelectronics STM32 adc"
+	depends on STM32_ADC_CORE
+	help
+	  Say yes here to build support for STMicroelectronics stm32 Analog
+	  to Digital Converter (ADC).
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called stm32-adc.
+
 config STX104
 	tristate "Apex Embedded Systems STX104 driver"
 	depends on X86 && ISA_BUS_API

drivers/iio/adc/Makefile

···
 obj-$(CONFIG_ROCKCHIP_SARADC) += rockchip_saradc.o
 obj-$(CONFIG_STX104) += stx104.o
 obj-$(CONFIG_STM32_ADC_CORE) += stm32-adc-core.o
+obj-$(CONFIG_STM32_ADC) += stm32-adc.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_ADC0832) += ti-adc0832.o
 obj-$(CONFIG_TI_ADC12138) += ti-adc12138.o

drivers/iio/adc/stm32-adc.c

···
+/*
+ * This file is part of STM32 ADC driver
+ *
+ * Copyright (C) 2016, STMicroelectronics - All Rights Reserved
+ * Author: Fabrice Gasnier <[e-mail]>.
+ *
+ * License type: GPLv2
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/iio/iio.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+
+#include "stm32-adc-core.h"
+
+/* STM32F4 - Registers for each ADC instance */
+#define STM32F4_ADC_SR			0x00
+#define STM32F4_ADC_CR1			0x04
+#define STM32F4_ADC_CR2			0x08
+#define STM32F4_ADC_SMPR1		0x0C
+#define STM32F4_ADC_SMPR2		0x10
+#define STM32F4_ADC_HTR			0x24
+#define STM32F4_ADC_LTR			0x28
+#define STM32F4_ADC_SQR1		0x2C
+#define STM32F4_ADC_SQR2		0x30
+#define STM32F4_ADC_SQR3		0x34
+#define STM32F4_ADC_JSQR		0x38
+#define STM32F4_ADC_JDR1		0x3C
+#define STM32F4_ADC_JDR2		0x40
+#define STM32F4_ADC_JDR3		0x44
+#define STM32F4_ADC_JDR4		0x48
+#define STM32F4_ADC_DR			0x4C
+
+/* STM32F4_ADC_SR - bit fields */
+#define STM32F4_STRT			BIT(4)
+#define STM32F4_EOC			BIT(1)
+
+/* STM32F4_ADC_CR1 - bit fields */
+#define STM32F4_SCAN			BIT(8)
+#define STM32F4_EOCIE			BIT(5)
+
+/* STM32F4_ADC_CR2 - bit fields */
+#define STM32F4_SWSTART			BIT(30)
+#define STM32F4_EXTEN_MASK		GENMASK(29, 28)
+#define STM32F4_EOCS			BIT(10)
+#define STM32F4_ADON			BIT(0)
+
+/* STM32F4_ADC_SQR1 - bit fields */
+#define STM32F4_L_SHIFT			20
+#define STM32F4_L_MASK			GENMASK(23, 20)
+
+/* STM32F4_ADC_SQR3 - bit fields */
+#define STM32F4_SQ1_SHIFT		0
+#define STM32F4_SQ1_MASK		GENMASK(4, 0)
+
+#define STM32_ADC_TIMEOUT_US		100000
+#define STM32_ADC_TIMEOUT	(msecs_to_jiffies(STM32_ADC_TIMEOUT_US / 1000))
+
+/**
+ * struct stm32_adc - private data of each ADC IIO instance
+ * @common:		reference to ADC block common data
+ * @offset:		ADC instance register offset in ADC block
+ * @completion:		end of single conversion completion
+ * @buffer:		data buffer
+ * @clk:		clock for this adc instance
+ * @irq:		interrupt for this adc instance
+ * @lock:		spinlock
+ */
+struct stm32_adc {
+	struct stm32_adc_common	*common;
+	u32			offset;
+	struct completion	completion;
+	u16			*buffer;
+	struct clk		*clk;
+	int			irq;
+	spinlock_t		lock;		/* interrupt lock */
+};
+
+/**
+ * struct stm32_adc_chan_spec - specification of stm32 adc channel
+ * @type:	IIO channel type
+ * @channel:	channel number (single ended)
+ * @name:	channel name (single ended)
+ */
+struct stm32_adc_chan_spec {
+	enum iio_chan_type	type;
+	int			channel;
+	const char		*name;
+};
+
+/* Input definitions common for all STM32F4 instances */
+static const struct stm32_adc_chan_spec stm32f4_adc123_channels[] = {
+	{ IIO_VOLTAGE, 0, "in0" },
+	{ IIO_VOLTAGE, 1, "in1" },
+	{ IIO_VOLTAGE, 2, "in2" },
+	{ IIO_VOLTAGE, 3, "in3" },
+	{ IIO_VOLTAGE, 4, "in4" },
+	{ IIO_VOLTAGE, 5, "in5" },
+	{ IIO_VOLTAGE, 6, "in6" },
+	{ IIO_VOLTAGE, 7, "in7" },
+	{ IIO_VOLTAGE, 8, "in8" },
+	{ IIO_VOLTAGE, 9, "in9" },
+	{ IIO_VOLTAGE, 10, "in10" },
+	{ IIO_VOLTAGE, 11, "in11" },
+	{ IIO_VOLTAGE, 12, "in12" },
+	{ IIO_VOLTAGE, 13, "in13" },
+	{ IIO_VOLTAGE, 14, "in14" },
+	{ IIO_VOLTAGE, 15, "in15" },
+};
+
+/**
+ * STM32 ADC registers access routines
+ * @adc: stm32 adc instance
+ * @reg: reg offset in adc instance
+ *
+ * Note: All instances share same base, with 0x0, 0x100 or 0x200 offset resp.
+ * for adc1, adc2 and adc3.
+ */
+static u32 stm32_adc_readl(struct stm32_adc *adc, u32 reg)
+{
+	return readl_relaxed(adc->common->base + adc->offset + reg);
+}
+
+static u16 stm32_adc_readw(struct stm32_adc *adc, u32 reg)
+{
+	return readw_relaxed(adc->common->base + adc->offset + reg);
+}
+
+static void stm32_adc_writel(struct stm32_adc *adc, u32 reg, u32 val)
+{
+	writel_relaxed(val, adc->common->base + adc->offset + reg);
+}
+
+static void stm32_adc_set_bits(struct stm32_adc *adc, u32 reg, u32 bits)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&adc->lock, flags);
+	stm32_adc_writel(adc, reg, stm32_adc_readl(adc, reg) | bits);
+	spin_unlock_irqrestore(&adc->lock, flags);
+}
+
+static void stm32_adc_clr_bits(struct stm32_adc *adc, u32 reg, u32 bits)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&adc->lock, flags);
+	stm32_adc_writel(adc, reg, stm32_adc_readl(adc, reg) & ~bits);
+	spin_unlock_irqrestore(&adc->lock, flags);
+}
+
+/**
+ * stm32_adc_conv_irq_enable() - Enable end of conversion interrupt
+ * @adc: stm32 adc instance
+ */
+static void stm32_adc_conv_irq_enable(struct stm32_adc *adc)
+{
+	stm32_adc_set_bits(adc, STM32F4_ADC_CR1, STM32F4_EOCIE);
+};
+
+/**
+ * stm32_adc_conv_irq_disable() - Disable end of conversion interrupt
+ * @adc: stm32 adc instance
+ */
+static void stm32_adc_conv_irq_disable(struct stm32_adc *adc)
+{
+	stm32_adc_clr_bits(adc, STM32F4_ADC_CR1, STM32F4_EOCIE);
+}
+
+/**
+ * stm32_adc_start_conv() - Start conversions for regular channels.
+ * @adc: stm32 adc instance
+ */
+static void stm32_adc_start_conv(struct stm32_adc *adc)
+{
+	stm32_adc_set_bits(adc, STM32F4_ADC_CR1, STM32F4_SCAN);
+	stm32_adc_set_bits(adc, STM32F4_ADC_CR2, STM32F4_EOCS | STM32F4_ADON);
+
+	/* Wait for Power-up time (tSTAB from datasheet) */
+	usleep_range(2, 3);
+
+	/* Software start ? (e.g. trigger detection disabled ?) */
+	if (!(stm32_adc_readl(adc, STM32F4_ADC_CR2) & STM32F4_EXTEN_MASK))
+		stm32_adc_set_bits(adc, STM32F4_ADC_CR2, STM32F4_SWSTART);
+}
+
+static void stm32_adc_stop_conv(struct stm32_adc *adc)
+{
+	stm32_adc_clr_bits(adc, STM32F4_ADC_CR2, STM32F4_EXTEN_MASK);
+	stm32_adc_clr_bits(adc, STM32F4_ADC_SR, STM32F4_STRT);
+
+	stm32_adc_clr_bits(adc, STM32F4_ADC_CR1, STM32F4_SCAN);
+	stm32_adc_clr_bits(adc, STM32F4_ADC_CR2, STM32F4_ADON);
+}
+
+/**
+ * stm32_adc_single_conv() - Performs a single conversion
+ * @indio_dev: IIO device
+ * @chan: IIO channel
+ * @res: conversion result
+ *
+ * The function performs a single conversion on a given channel:
+ * - Program sequencer with one channel (e.g. in SQ1 with len = 1)
+ * - Use SW trigger
+ * - Start conversion, then wait for interrupt completion.
+ */
+static int stm32_adc_single_conv(struct iio_dev *indio_dev,
+				 const struct iio_chan_spec *chan,
+				 int *res)
+{
+	struct stm32_adc *adc = iio_priv(indio_dev);
+	long timeout;
+	u32 val;
+	u16 result;
+	int ret;
+
+	reinit_completion(&adc->completion);
+
+	adc->buffer = &result;
+
+	/* Program chan number in regular sequence */
+	val = stm32_adc_readl(adc, STM32F4_ADC_SQR3);
+	val &= ~STM32F4_SQ1_MASK;
+	val |= chan->channel << STM32F4_SQ1_SHIFT;
+	stm32_adc_writel(adc, STM32F4_ADC_SQR3, val);
+
+	/* Set regular sequence len (0 for 1 conversion) */
+	stm32_adc_clr_bits(adc, STM32F4_ADC_SQR1, STM32F4_L_MASK);
+
+	/* Trigger detection disabled (conversion can be launched in SW) */
+	stm32_adc_clr_bits(adc, STM32F4_ADC_CR2, STM32F4_EXTEN_MASK);
+
+	stm32_adc_conv_irq_enable(adc);
+
+	stm32_adc_start_conv(adc);
+
+	timeout = wait_for_completion_interruptible_timeout(
+					&adc->completion, STM32_ADC_TIMEOUT);
+	if (timeout == 0) {
+		ret = -ETIMEDOUT;
+	} else if (timeout < 0) {
+		ret = timeout;
+	} else {
+		*res = result;
+		ret = IIO_VAL_INT;
+	}
+
+	stm32_adc_stop_conv(adc);
+
+	stm32_adc_conv_irq_disable(adc);
+
+	return ret;
+}
+
+static int stm32_adc_read_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      int *val, int *val2, long mask)
+{
+	struct stm32_adc *adc = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret)
+			return ret;
+		if (chan->type == IIO_VOLTAGE)
+			ret = stm32_adc_single_conv(indio_dev, chan, val);
+		else
+			ret = -EINVAL;
+		iio_device_release_direct_mode(indio_dev);
+		return ret;
+
+	case IIO_CHAN_INFO_SCALE:
+		*val = adc->common->vref_mv;
+		*val2 = chan->scan_type.realbits;
+		return IIO_VAL_FRACTIONAL_LOG2;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static irqreturn_t stm32_adc_isr(int irq, void *data)
+{
+	struct stm32_adc *adc = data;
+	u32 status = stm32_adc_readl(adc, STM32F4_ADC_SR);
+
+	if (status & STM32F4_EOC) {
+		*adc->buffer = stm32_adc_readw(adc, STM32F4_ADC_DR);
+		complete(&adc->completion);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int stm32_adc_of_xlate(struct iio_dev *indio_dev,
+			      const struct of_phandle_args *iiospec)
+{
+	int i;
+
+	for (i = 0; i < indio_dev->num_channels; i++)
+		if (indio_dev->channels[i].channel == iiospec->args[0])
+			return i;
+
+	return -EINVAL;
+}
+
+/**
+ * stm32_adc_debugfs_reg_access - read or write register value
+ *
+ * To read a value from an ADC register:
+ *   echo [ADC reg offset] > direct_reg_access
+ *   cat direct_reg_access
+ *
+ * To write a value in a ADC register:
+ *   echo [ADC_reg_offset] [value] > direct_reg_access
+ */
+static int stm32_adc_debugfs_reg_access(struct iio_dev *indio_dev,
+					unsigned reg, unsigned writeval,
+					unsigned *readval)
+{
+	struct stm32_adc *adc = iio_priv(indio_dev);
+
+	if (!readval)
+		stm32_adc_writel(adc, reg, writeval);
+	else
+		*readval = stm32_adc_readl(adc, reg);
+
+	return 0;
+}
+
+static const struct iio_info stm32_adc_iio_info = {
+	.read_raw = stm32_adc_read_raw,
+	.debugfs_reg_access = stm32_adc_debugfs_reg_access,
+	.of_xlate = stm32_adc_of_xlate,
+	.driver_module = THIS_MODULE,
+};
+
+static void stm32_adc_chan_init_one(struct iio_dev *indio_dev,
+				    struct iio_chan_spec *chan,
+				    const struct stm32_adc_chan_spec *channel,
+				    int scan_index)
+{
+	chan->type = channel->type;
+	chan->channel = channel->channel;
+	chan->datasheet_name = channel->name;
+	chan->scan_index = scan_index;
+	chan->indexed = 1;
+	chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
+	chan->info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE);
+	chan->scan_type.sign = 'u';
+	chan->scan_type.realbits = 12;
+	chan->scan_type.storagebits = 16;
+}
+
+static int stm32_adc_chan_of_init(struct iio_dev *indio_dev)
+{
+	struct device_node *node = indio_dev->dev.of_node;
+	struct property *prop;
+	const __be32 *cur;
+	struct iio_chan_spec *channels;
+	int scan_index = 0, num_channels;
+	u32 val;
+
+	num_channels = of_property_count_u32_elems(node, "st,adc-channels");
+	if (num_channels < 0 ||
+	    num_channels >= ARRAY_SIZE(stm32f4_adc123_channels)) {
+		dev_err(&indio_dev->dev, "Bad st,adc-channels?\n");
+		return num_channels < 0 ? num_channels : -EINVAL;
+	}
+
+	channels = devm_kcalloc(&indio_dev->dev, num_channels,
+				sizeof(struct iio_chan_spec), GFP_KERNEL);
+	if (!channels)
+		return -ENOMEM;
+
+	of_property_for_each_u32(node, "st,adc-channels", prop, cur, val) {
+		if (val >= ARRAY_SIZE(stm32f4_adc123_channels)) {
+			dev_err(&indio_dev->dev, "Invalid channel %d\n", val);
+			return -EINVAL;
+		}
+		stm32_adc_chan_init_one(indio_dev, &channels[scan_index],
+					&stm32f4_adc123_channels[val],
+					scan_index);
+		scan_index++;
+	}
+
+	indio_dev->num_channels = scan_index;
+	indio_dev->channels = channels;
+
+	return 0;
+}
+
+static int stm32_adc_probe(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev;
+	struct stm32_adc *adc;
+	int ret;
+
+	if (!pdev->dev.of_node)
+		return -ENODEV;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*adc));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	adc = iio_priv(indio_dev);
+	adc->common = dev_get_drvdata(pdev->dev.parent);
+	spin_lock_init(&adc->lock);
+	init_completion(&adc->completion);
+
+	indio_dev->name = dev_name(&pdev->dev);
+	indio_dev->dev.parent = &pdev->dev;
+	indio_dev->dev.of_node = pdev->dev.of_node;
+	indio_dev->info = &stm32_adc_iio_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	platform_set_drvdata(pdev, adc);
+
+	ret = of_property_read_u32(pdev->dev.of_node, "reg", &adc->offset);
+	if (ret != 0) {
+		dev_err(&pdev->dev, "missing reg property\n");
+		return -EINVAL;
+	}
+
+	adc->irq = platform_get_irq(pdev, 0);
+	if (adc->irq < 0) {
+		dev_err(&pdev->dev, "failed to get irq\n");
+		return adc->irq;
+	}
+
+	ret = devm_request_irq(&pdev->dev, adc->irq, stm32_adc_isr,
+			       0, pdev->name, adc);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to request IRQ\n");
+		return ret;
+	}
+
+	adc->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(adc->clk)) {
+		dev_err(&pdev->dev, "Can't get clock\n");
+		return PTR_ERR(adc->clk);
+	}
+
+	ret = clk_prepare_enable(adc->clk);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "clk enable failed\n");
+		return ret;
+	}
+
+	ret = stm32_adc_chan_of_init(indio_dev);
+	if (ret < 0)
+		goto err_clk_disable;
+
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		dev_err(&pdev->dev, "iio dev register failed\n");
+		goto err_clk_disable;
+	}
+
+	return 0;
+
+err_clk_disable:
+	clk_disable_unprepare(adc->clk);
+
+	return ret;
+}
+
+static int stm32_adc_remove(struct platform_device *pdev)
+{
+	struct stm32_adc *adc = platform_get_drvdata(pdev);
+	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
+
+	iio_device_unregister(indio_dev);
+	clk_disable_unprepare(adc->clk);
+
+	return 0;
+}
+
+static const struct of_device_id stm32_adc_of_match[] = {
+	{ .compatible = "st,stm32f4-adc" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm32_adc_of_match);
+
+static struct platform_driver stm32_adc_driver = {
+	.probe = stm32_adc_probe,
+	.remove = stm32_adc_remove,
+	.driver = {
+		.name = "stm32-adc",
+		.of_match_table = stm32_adc_of_match,
+	},
+};
+module_platform_driver(stm32_adc_driver);
+
+MODULE_AUTHOR("Fabrice Gasnier <[e-mail]>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 ADC IIO driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:stm32-adc");