/*
   * 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 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) {
  		dev_dbg(&pdev->dev, "out of memory
  ");
  		return -ENOMEM;
  	}
  
  	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (!regs) {
  		dev_dbg(&pdev->dev, "no mmio resource defined
  ");
  		return -ENXIO;
  	}
  
  	irq = platform_get_irq(pdev, 0);
  	if (irq <= 0) {
  		dev_dbg(&pdev->dev, "could not get irq
  ");
  		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
  ");
  		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
  ", 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
  ");
  		return PTR_ERR(rtc->rtc);
  	}
  
  	device_init_wakeup(&pdev->dev, 1);
  
  	dev_info(&pdev->dev, "Atmel RTC for AT32AP700x at %08lx irq %ld
  ",
  			(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",
  		.owner	= THIS_MODULE,
  	},
  };
  
  module_platform_driver_probe(at32_rtc_driver, at32_rtc_probe);
  
  MODULE_AUTHOR("Hans-Christian Egtvedt <hcegtvedt@atmel.com>");
  MODULE_DESCRIPTION("Real time clock for AVR32 AT32AP700x");
  MODULE_LICENSE("GPL");