/*
 * This file is part of STM32 ADC driver
 *
 * Copyright (C) 2016, STMicroelectronics - All Rights Reserved
 * Author: Fabrice Gasnier <fabrice.gasnier@st.com>.
 *
 * 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 <fabrice.gasnier@st.com>");
MODULE_DESCRIPTION("STMicroelectronics STM32 ADC IIO driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:stm32-adc");