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/*
 * MOXA ART RTC driver.
 *
 * Copyright (C) 2013 Jonas Jensen
 *
 * Jonas Jensen <jonas.jensen@gmail.com>
 *
 * Based on code from
 * Moxa Technology Co., Ltd. <www.moxa.com>
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2.  This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/rtc.h>
#include <linux/platform_device.h>
#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>

#define GPIO_RTC_RESERVED			0x0C
#define GPIO_RTC_DATA_SET			0x10
#define GPIO_RTC_DATA_CLEAR			0x14
#define GPIO_RTC_PIN_PULL_ENABLE		0x18
#define GPIO_RTC_PIN_PULL_TYPE			0x1C
#define GPIO_RTC_INT_ENABLE			0x20
#define GPIO_RTC_INT_RAW_STATE			0x24
#define GPIO_RTC_INT_MASKED_STATE		0x28
#define GPIO_RTC_INT_MASK			0x2C
#define GPIO_RTC_INT_CLEAR			0x30
#define GPIO_RTC_INT_TRIGGER			0x34
#define GPIO_RTC_INT_BOTH			0x38
#define GPIO_RTC_INT_RISE_NEG			0x3C
#define GPIO_RTC_BOUNCE_ENABLE			0x40
#define GPIO_RTC_BOUNCE_PRE_SCALE		0x44
#define GPIO_RTC_PROTECT_W			0x8E
#define GPIO_RTC_PROTECT_R			0x8F
#define GPIO_RTC_YEAR_W				0x8C
#define GPIO_RTC_YEAR_R				0x8D
#define GPIO_RTC_DAY_W				0x8A
#define GPIO_RTC_DAY_R				0x8B
#define GPIO_RTC_MONTH_W			0x88
#define GPIO_RTC_MONTH_R			0x89
#define GPIO_RTC_DATE_W				0x86
#define GPIO_RTC_DATE_R				0x87
#define GPIO_RTC_HOURS_W			0x84
#define GPIO_RTC_HOURS_R			0x85
#define GPIO_RTC_MINUTES_W			0x82
#define GPIO_RTC_MINUTES_R			0x83
#define GPIO_RTC_SECONDS_W			0x80
#define GPIO_RTC_SECONDS_R			0x81
#define GPIO_RTC_DELAY_TIME			8

struct moxart_rtc {
	struct rtc_device *rtc;
	spinlock_t rtc_lock;
	int gpio_data, gpio_sclk, gpio_reset;
};

static int day_of_year[12] =	{ 0, 31, 59, 90, 120, 151, 181,
				  212, 243, 273, 304, 334 };

static void moxart_rtc_write_byte(struct device *dev, u8 data)
{
	struct moxart_rtc *moxart_rtc = dev_get_drvdata(dev);
	int i;

	for (i = 0; i < 8; i++, data >>= 1) {
		gpio_set_value(moxart_rtc->gpio_sclk, 0);
		gpio_set_value(moxart_rtc->gpio_data, ((data & 1) == 1));
		udelay(GPIO_RTC_DELAY_TIME);
		gpio_set_value(moxart_rtc->gpio_sclk, 1);
		udelay(GPIO_RTC_DELAY_TIME);
	}
}

static u8 moxart_rtc_read_byte(struct device *dev)
{
	struct moxart_rtc *moxart_rtc = dev_get_drvdata(dev);
	int i;
	u8 data = 0;

	for (i = 0; i < 8; i++) {
		gpio_set_value(moxart_rtc->gpio_sclk, 0);
		udelay(GPIO_RTC_DELAY_TIME);
		gpio_set_value(moxart_rtc->gpio_sclk, 1);
		udelay(GPIO_RTC_DELAY_TIME);
		if (gpio_get_value(moxart_rtc->gpio_data))
			data |= (1 << i);
		udelay(GPIO_RTC_DELAY_TIME);
	}
	return data;
}

static u8 moxart_rtc_read_register(struct device *dev, u8 cmd)
{
	struct moxart_rtc *moxart_rtc = dev_get_drvdata(dev);
	u8 data;
	unsigned long flags;

	local_irq_save(flags);

	gpio_direction_output(moxart_rtc->gpio_data, 0);
	gpio_set_value(moxart_rtc->gpio_reset, 1);
	udelay(GPIO_RTC_DELAY_TIME);
	moxart_rtc_write_byte(dev, cmd);
	gpio_direction_input(moxart_rtc->gpio_data);
	udelay(GPIO_RTC_DELAY_TIME);
	data = moxart_rtc_read_byte(dev);
	gpio_set_value(moxart_rtc->gpio_sclk, 0);
	gpio_set_value(moxart_rtc->gpio_reset, 0);
	udelay(GPIO_RTC_DELAY_TIME);

	local_irq_restore(flags);

	return data;
}

static void moxart_rtc_write_register(struct device *dev, u8 cmd, u8 data)
{
	struct moxart_rtc *moxart_rtc = dev_get_drvdata(dev);
	unsigned long flags;

	local_irq_save(flags);

	gpio_direction_output(moxart_rtc->gpio_data, 0);
	gpio_set_value(moxart_rtc->gpio_reset, 1);
	udelay(GPIO_RTC_DELAY_TIME);
	moxart_rtc_write_byte(dev, cmd);
	moxart_rtc_write_byte(dev, data);
	gpio_set_value(moxart_rtc->gpio_sclk, 0);
	gpio_set_value(moxart_rtc->gpio_reset, 0);
	udelay(GPIO_RTC_DELAY_TIME);

	local_irq_restore(flags);
}

static int moxart_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct moxart_rtc *moxart_rtc = dev_get_drvdata(dev);

	spin_lock_irq(&moxart_rtc->rtc_lock);

	moxart_rtc_write_register(dev, GPIO_RTC_PROTECT_W, 0);
	moxart_rtc_write_register(dev, GPIO_RTC_YEAR_W,
				  (((tm->tm_year - 100) / 10) << 4) |
				  ((tm->tm_year - 100) % 10));

	moxart_rtc_write_register(dev, GPIO_RTC_MONTH_W,
				  (((tm->tm_mon + 1) / 10) << 4) |
				  ((tm->tm_mon + 1) % 10));

	moxart_rtc_write_register(dev, GPIO_RTC_DATE_W,
				  ((tm->tm_mday / 10) << 4) |
				  (tm->tm_mday % 10));

	moxart_rtc_write_register(dev, GPIO_RTC_HOURS_W,
				  ((tm->tm_hour / 10) << 4) |
				  (tm->tm_hour % 10));

	moxart_rtc_write_register(dev, GPIO_RTC_MINUTES_W,
				  ((tm->tm_min / 10) << 4) |
				  (tm->tm_min % 10));

	moxart_rtc_write_register(dev, GPIO_RTC_SECONDS_W,
				  ((tm->tm_sec / 10) << 4) |
				  (tm->tm_sec % 10));

	moxart_rtc_write_register(dev, GPIO_RTC_PROTECT_W, 0x80);

	spin_unlock_irq(&moxart_rtc->rtc_lock);

	dev_dbg(dev, "%s: success tm_year=%d tm_mon=%d\n"
		"tm_mday=%d tm_hour=%d tm_min=%d tm_sec=%d\n",
		__func__, tm->tm_year, tm->tm_mon, tm->tm_mday,
		tm->tm_hour, tm->tm_min, tm->tm_sec);

	return 0;
}

static int moxart_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct moxart_rtc *moxart_rtc = dev_get_drvdata(dev);
	unsigned char v;

	spin_lock_irq(&moxart_rtc->rtc_lock);

	v = moxart_rtc_read_register(dev, GPIO_RTC_SECONDS_R);
	tm->tm_sec = (((v & 0x70) >> 4) * 10) + (v & 0x0F);

	v = moxart_rtc_read_register(dev, GPIO_RTC_MINUTES_R);
	tm->tm_min = (((v & 0x70) >> 4) * 10) + (v & 0x0F);

	v = moxart_rtc_read_register(dev, GPIO_RTC_HOURS_R);
	if (v & 0x80) { /* 12-hour mode */
		tm->tm_hour = (((v & 0x10) >> 4) * 10) + (v & 0x0F);
		if (v & 0x20) { /* PM mode */
			tm->tm_hour += 12;
			if (tm->tm_hour >= 24)
				tm->tm_hour = 0;
		}
	} else { /* 24-hour mode */
		tm->tm_hour = (((v & 0x30) >> 4) * 10) + (v & 0x0F);
	}

	v = moxart_rtc_read_register(dev, GPIO_RTC_DATE_R);
	tm->tm_mday = (((v & 0x30) >> 4) * 10) + (v & 0x0F);

	v = moxart_rtc_read_register(dev, GPIO_RTC_MONTH_R);
	tm->tm_mon = (((v & 0x10) >> 4) * 10) + (v & 0x0F);
	tm->tm_mon--;

	v = moxart_rtc_read_register(dev, GPIO_RTC_YEAR_R);
	tm->tm_year = (((v & 0xF0) >> 4) * 10) + (v & 0x0F);
	tm->tm_year += 100;
	if (tm->tm_year <= 69)
		tm->tm_year += 100;

	v = moxart_rtc_read_register(dev, GPIO_RTC_DAY_R);
	tm->tm_wday = (v & 0x0f) - 1;
	tm->tm_yday = day_of_year[tm->tm_mon];
	tm->tm_yday += (tm->tm_mday - 1);
	if (tm->tm_mon >= 2) {
		if (!(tm->tm_year % 4) && (tm->tm_year % 100))
			tm->tm_yday++;
	}

	tm->tm_isdst = 0;

	spin_unlock_irq(&moxart_rtc->rtc_lock);

	return 0;
}

static const struct rtc_class_ops moxart_rtc_ops = {
	.read_time	= moxart_rtc_read_time,
	.set_time	= moxart_rtc_set_time,
};

static int moxart_rtc_probe(struct platform_device *pdev)
{
	struct moxart_rtc *moxart_rtc;
	int ret = 0;

	moxart_rtc = devm_kzalloc(&pdev->dev, sizeof(*moxart_rtc), GFP_KERNEL);
	if (!moxart_rtc)
		return -ENOMEM;

	moxart_rtc->gpio_data = of_get_named_gpio(pdev->dev.of_node,
						  "gpio-rtc-data", 0);
	if (!gpio_is_valid(moxart_rtc->gpio_data)) {
		dev_err(&pdev->dev, "invalid gpio (data): %d\n",
			moxart_rtc->gpio_data);
		return moxart_rtc->gpio_data;
	}

	moxart_rtc->gpio_sclk = of_get_named_gpio(pdev->dev.of_node,
						  "gpio-rtc-sclk", 0);
	if (!gpio_is_valid(moxart_rtc->gpio_sclk)) {
		dev_err(&pdev->dev, "invalid gpio (sclk): %d\n",
			moxart_rtc->gpio_sclk);
		return moxart_rtc->gpio_sclk;
	}

	moxart_rtc->gpio_reset = of_get_named_gpio(pdev->dev.of_node,
						   "gpio-rtc-reset", 0);
	if (!gpio_is_valid(moxart_rtc->gpio_reset)) {
		dev_err(&pdev->dev, "invalid gpio (reset): %d\n",
			moxart_rtc->gpio_reset);
		return moxart_rtc->gpio_reset;
	}

	spin_lock_init(&moxart_rtc->rtc_lock);
	platform_set_drvdata(pdev, moxart_rtc);

	ret = devm_gpio_request(&pdev->dev, moxart_rtc->gpio_data, "rtc_data");
	if (ret) {
		dev_err(&pdev->dev, "can't get rtc_data gpio\n");
		return ret;
	}

	ret = devm_gpio_request_one(&pdev->dev, moxart_rtc->gpio_sclk,
				    GPIOF_DIR_OUT, "rtc_sclk");
	if (ret) {
		dev_err(&pdev->dev, "can't get rtc_sclk gpio\n");
		return ret;
	}

	ret = devm_gpio_request_one(&pdev->dev, moxart_rtc->gpio_reset,
				    GPIOF_DIR_OUT, "rtc_reset");
	if (ret) {
		dev_err(&pdev->dev, "can't get rtc_reset gpio\n");
		return ret;
	}

	moxart_rtc->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
						   &moxart_rtc_ops,
						   THIS_MODULE);
	if (IS_ERR(moxart_rtc->rtc)) {
		dev_err(&pdev->dev, "devm_rtc_device_register failed\n");
		return PTR_ERR(moxart_rtc->rtc);
	}

	return 0;
}

static const struct of_device_id moxart_rtc_match[] = {
	{ .compatible = "moxa,moxart-rtc" },
	{ },
};
MODULE_DEVICE_TABLE(of, moxart_rtc_match);

static struct platform_driver moxart_rtc_driver = {
	.probe	= moxart_rtc_probe,
	.driver	= {
		.name		= "moxart-rtc",
		.of_match_table	= moxart_rtc_match,
	},
};
module_platform_driver(moxart_rtc_driver);

MODULE_DESCRIPTION("MOXART RTC driver");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jonas Jensen <jonas.jensen@gmail.com>");