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/*
 * An RTC driver for the AVR32 AT32AP700x processor series.
 *
 * Copyright (C) 2007 Atmel Corporation
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/rtc.h>
#include <linux/io.h>

/*
 * This is a bare-bones RTC. It runs during most system sleep states, but has
 * no battery backup and gets reset during system restart.  It must be
 * initialized from an external clock (network, I2C, etc) before it can be of
 * much use.
 *
 * The alarm functionality is limited by the hardware, not supporting
 * periodic interrupts.
 */

#define RTC_CTRL		0x00
#define RTC_CTRL_EN		   0
#define RTC_CTRL_PCLR		   1
#define RTC_CTRL_TOPEN		   2
#define RTC_CTRL_PSEL		   8

#define RTC_VAL			0x04

#define RTC_TOP			0x08

#define RTC_IER			0x10
#define RTC_IER_TOPI		   0

#define RTC_IDR			0x14
#define RTC_IDR_TOPI		   0

#define RTC_IMR			0x18
#define RTC_IMR_TOPI		   0

#define RTC_ISR			0x1c
#define RTC_ISR_TOPI		   0

#define RTC_ICR			0x20
#define RTC_ICR_TOPI		   0

#define RTC_BIT(name)		(1 << RTC_##name)
#define RTC_BF(name, value)	((value) << RTC_##name)

#define rtc_readl(dev, reg)				\
	__raw_readl((dev)->regs + RTC_##reg)
#define rtc_writel(dev, reg, value)			\
	__raw_writel((value), (dev)->regs + RTC_##reg)

struct rtc_at32ap700x {
	struct rtc_device	*rtc;
	void __iomem		*regs;
	unsigned long		alarm_time;
	unsigned long		irq;
	/* Protect against concurrent register access. */
	spinlock_t		lock;
};

static int at32_rtc_readtime(struct device *dev, struct rtc_time *tm)
{
	struct rtc_at32ap700x *rtc = dev_get_drvdata(dev);
	unsigned long now;

	now = rtc_readl(rtc, VAL);
	rtc_time_to_tm(now, tm);

	return 0;
}

static int at32_rtc_settime(struct device *dev, struct rtc_time *tm)
{
	struct rtc_at32ap700x *rtc = dev_get_drvdata(dev);
	unsigned long now;
	int ret;

	ret = rtc_tm_to_time(tm, &now);
	if (ret == 0)
		rtc_writel(rtc, VAL, now);

	return ret;
}

static int at32_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct rtc_at32ap700x *rtc = dev_get_drvdata(dev);

	spin_lock_irq(&rtc->lock);
	rtc_time_to_tm(rtc->alarm_time, &alrm->time);
	alrm->enabled = rtc_readl(rtc, IMR) & RTC_BIT(IMR_TOPI) ? 1 : 0;
	alrm->pending = rtc_readl(rtc, ISR) & RTC_BIT(ISR_TOPI) ? 1 : 0;
	spin_unlock_irq(&rtc->lock);

	return 0;
}

static int at32_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct rtc_at32ap700x *rtc = dev_get_drvdata(dev);
	unsigned long rtc_unix_time;
	unsigned long alarm_unix_time;
	int ret;

	rtc_unix_time = rtc_readl(rtc, VAL);

	ret = rtc_tm_to_time(&alrm->time, &alarm_unix_time);
	if (ret)
		return ret;

	if (alarm_unix_time < rtc_unix_time)
		return -EINVAL;

	spin_lock_irq(&rtc->lock);
	rtc->alarm_time = alarm_unix_time;
	rtc_writel(rtc, TOP, rtc->alarm_time);
	if (alrm->enabled)
		rtc_writel(rtc, CTRL, rtc_readl(rtc, CTRL)
				| RTC_BIT(CTRL_TOPEN));
	else
		rtc_writel(rtc, CTRL, rtc_readl(rtc, CTRL)
				& ~RTC_BIT(CTRL_TOPEN));
	spin_unlock_irq(&rtc->lock);

	return ret;
}

static int at32_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
	struct rtc_at32ap700x *rtc = dev_get_drvdata(dev);
	int ret = 0;

	spin_lock_irq(&rtc->lock);

	if (enabled) {
		if (rtc_readl(rtc, VAL) > rtc->alarm_time) {
			ret = -EINVAL;
			goto out;
		}
		rtc_writel(rtc, CTRL, rtc_readl(rtc, CTRL)
				| RTC_BIT(CTRL_TOPEN));
		rtc_writel(rtc, ICR, RTC_BIT(ICR_TOPI));
		rtc_writel(rtc, IER, RTC_BIT(IER_TOPI));
	} else {
		rtc_writel(rtc, CTRL, rtc_readl(rtc, CTRL)
				& ~RTC_BIT(CTRL_TOPEN));
		rtc_writel(rtc, IDR, RTC_BIT(IDR_TOPI));
		rtc_writel(rtc, ICR, RTC_BIT(ICR_TOPI));
	}
out:
	spin_unlock_irq(&rtc->lock);

	return ret;
}

static irqreturn_t at32_rtc_interrupt(int irq, void *dev_id)
{
	struct rtc_at32ap700x *rtc = (struct rtc_at32ap700x *)dev_id;
	unsigned long isr = rtc_readl(rtc, ISR);
	unsigned long events = 0;
	int ret = IRQ_NONE;

	spin_lock(&rtc->lock);

	if (isr & RTC_BIT(ISR_TOPI)) {
		rtc_writel(rtc, ICR, RTC_BIT(ICR_TOPI));
		rtc_writel(rtc, IDR, RTC_BIT(IDR_TOPI));
		rtc_writel(rtc, CTRL, rtc_readl(rtc, CTRL)
				& ~RTC_BIT(CTRL_TOPEN));
		rtc_writel(rtc, VAL, rtc->alarm_time);
		events = RTC_AF | RTC_IRQF;
		rtc_update_irq(rtc->rtc, 1, events);
		ret = IRQ_HANDLED;
	}

	spin_unlock(&rtc->lock);

	return ret;
}

static const struct rtc_class_ops at32_rtc_ops = {
	.read_time	= at32_rtc_readtime,
	.set_time	= at32_rtc_settime,
	.read_alarm	= at32_rtc_readalarm,
	.set_alarm	= at32_rtc_setalarm,
	.alarm_irq_enable = at32_rtc_alarm_irq_enable,
};

static int __init at32_rtc_probe(struct platform_device *pdev)
{
	struct resource	*regs;
	struct rtc_at32ap700x *rtc;
	int irq;
	int ret;

	rtc = devm_kzalloc(&pdev->dev, sizeof(struct rtc_at32ap700x),
			   GFP_KERNEL);
	if (!rtc)
		return -ENOMEM;

	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!regs) {
		dev_dbg(&pdev->dev, "no mmio resource defined\n");
		return -ENXIO;
	}

	irq = platform_get_irq(pdev, 0);
	if (irq <= 0) {
		dev_dbg(&pdev->dev, "could not get irq\n");
		return -ENXIO;
	}

	rtc->irq = irq;
	rtc->regs = devm_ioremap(&pdev->dev, regs->start, resource_size(regs));
	if (!rtc->regs) {
		dev_dbg(&pdev->dev, "could not map I/O memory\n");
		return -ENOMEM;
	}
	spin_lock_init(&rtc->lock);

	/*
	 * Maybe init RTC: count from zero at 1 Hz, disable wrap irq.
	 *
	 * Do not reset VAL register, as it can hold an old time
	 * from last JTAG reset.
	 */
	if (!(rtc_readl(rtc, CTRL) & RTC_BIT(CTRL_EN))) {
		rtc_writel(rtc, CTRL, RTC_BIT(CTRL_PCLR));
		rtc_writel(rtc, IDR, RTC_BIT(IDR_TOPI));
		rtc_writel(rtc, CTRL, RTC_BF(CTRL_PSEL, 0xe)
				| RTC_BIT(CTRL_EN));
	}

	ret = devm_request_irq(&pdev->dev, irq, at32_rtc_interrupt, IRQF_SHARED,
				"rtc", rtc);
	if (ret) {
		dev_dbg(&pdev->dev, "could not request irq %d\n", irq);
		return ret;
	}

	platform_set_drvdata(pdev, rtc);

	rtc->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
				&at32_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtc->rtc)) {
		dev_dbg(&pdev->dev, "could not register rtc device\n");
		return PTR_ERR(rtc->rtc);
	}

	device_init_wakeup(&pdev->dev, 1);

	dev_info(&pdev->dev, "Atmel RTC for AT32AP700x at %08lx irq %ld\n",
			(unsigned long)rtc->regs, rtc->irq);

	return 0;
}

static int __exit at32_rtc_remove(struct platform_device *pdev)
{
	device_init_wakeup(&pdev->dev, 0);

	return 0;
}

MODULE_ALIAS("platform:at32ap700x_rtc");

static struct platform_driver at32_rtc_driver = {
	.remove		= __exit_p(at32_rtc_remove),
	.driver		= {
		.name	= "at32ap700x_rtc",
	},
};

module_platform_driver_probe(at32_rtc_driver, at32_rtc_probe);

MODULE_AUTHOR("Hans-Christian Egtvedt <egtvedt@samfundet.no>");
MODULE_DESCRIPTION("Real time clock for AVR32 AT32AP700x");
MODULE_LICENSE("GPL");