/*
   * An RTC driver for the NVIDIA Tegra 200 series internal RTC.
   *
   * Copyright (c) 2010, NVIDIA Corporation.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * 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, write to the Free Software Foundation, Inc.,
   * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
   */
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/irq.h>
  #include <linux/io.h>
  #include <linux/delay.h>
  #include <linux/rtc.h>
  #include <linux/platform_device.h>
  #include <linux/pm.h>
  
  /* set to 1 = busy every eight 32kHz clocks during copy of sec+msec to AHB */
  #define TEGRA_RTC_REG_BUSY			0x004
  #define TEGRA_RTC_REG_SECONDS			0x008
  /* when msec is read, the seconds are buffered into shadow seconds. */
  #define TEGRA_RTC_REG_SHADOW_SECONDS		0x00c
  #define TEGRA_RTC_REG_MILLI_SECONDS		0x010
  #define TEGRA_RTC_REG_SECONDS_ALARM0		0x014
  #define TEGRA_RTC_REG_SECONDS_ALARM1		0x018
  #define TEGRA_RTC_REG_MILLI_SECONDS_ALARM0	0x01c
  #define TEGRA_RTC_REG_INTR_MASK			0x028
  /* write 1 bits to clear status bits */
  #define TEGRA_RTC_REG_INTR_STATUS		0x02c
  
  /* bits in INTR_MASK */
  #define TEGRA_RTC_INTR_MASK_MSEC_CDN_ALARM	(1<<4)
  #define TEGRA_RTC_INTR_MASK_SEC_CDN_ALARM	(1<<3)
  #define TEGRA_RTC_INTR_MASK_MSEC_ALARM		(1<<2)
  #define TEGRA_RTC_INTR_MASK_SEC_ALARM1		(1<<1)
  #define TEGRA_RTC_INTR_MASK_SEC_ALARM0		(1<<0)
  
  /* bits in INTR_STATUS */
  #define TEGRA_RTC_INTR_STATUS_MSEC_CDN_ALARM	(1<<4)
  #define TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM	(1<<3)
  #define TEGRA_RTC_INTR_STATUS_MSEC_ALARM	(1<<2)
  #define TEGRA_RTC_INTR_STATUS_SEC_ALARM1	(1<<1)
  #define TEGRA_RTC_INTR_STATUS_SEC_ALARM0	(1<<0)
  
  struct tegra_rtc_info {
  	struct platform_device	*pdev;
  	struct rtc_device	*rtc_dev;
  	void __iomem		*rtc_base; /* NULL if not initialized. */
  	int			tegra_rtc_irq; /* alarm and periodic irq */
  	spinlock_t		tegra_rtc_lock;
  };
  
  /* RTC hardware is busy when it is updating its values over AHB once
   * every eight 32kHz clocks (~250uS).
   * outside of these updates the CPU is free to write.
   * CPU is always free to read.
   */
  static inline u32 tegra_rtc_check_busy(struct tegra_rtc_info *info)
  {
  	return readl(info->rtc_base + TEGRA_RTC_REG_BUSY) & 1;
  }
  
  /* Wait for hardware to be ready for writing.
   * This function tries to maximize the amount of time before the next update.
   * It does this by waiting for the RTC to become busy with its periodic update,
   * then returning once the RTC first becomes not busy.
   * This periodic update (where the seconds and milliseconds are copied to the
   * AHB side) occurs every eight 32kHz clocks (~250uS).
   * The behavior of this function allows us to make some assumptions without
   * introducing a race, because 250uS is plenty of time to read/write a value.
   */
  static int tegra_rtc_wait_while_busy(struct device *dev)
  {
  	struct tegra_rtc_info *info = dev_get_drvdata(dev);
  
  	int retries = 500; /* ~490 us is the worst case, ~250 us is best. */
  
  	/* first wait for the RTC to become busy. this is when it
  	 * posts its updated seconds+msec registers to AHB side. */
  	while (tegra_rtc_check_busy(info)) {
  		if (!retries--)
  			goto retry_failed;
  		udelay(1);
  	}
  
  	/* now we have about 250 us to manipulate registers */
  	return 0;
  
  retry_failed:
  	dev_err(dev, "write failed:retry count exceeded.
  ");
  	return -ETIMEDOUT;
  }
  
  static int tegra_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {
  	struct tegra_rtc_info *info = dev_get_drvdata(dev);
  	unsigned long sec, msec;
  	unsigned long sl_irq_flags;
  
  	/* RTC hardware copies seconds to shadow seconds when a read
  	 * of milliseconds occurs. use a lock to keep other threads out. */
  	spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
  
  	msec = readl(info->rtc_base + TEGRA_RTC_REG_MILLI_SECONDS);
  	sec = readl(info->rtc_base + TEGRA_RTC_REG_SHADOW_SECONDS);
  
  	spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
  
  	rtc_time_to_tm(sec, tm);
  
  	dev_vdbg(dev, "time read as %lu. %d/%d/%d %d:%02u:%02u
  ",
  		sec,
  		tm->tm_mon + 1,
  		tm->tm_mday,
  		tm->tm_year + 1900,
  		tm->tm_hour,
  		tm->tm_min,
  		tm->tm_sec
  	);
  
  	return 0;
  }
  
  static int tegra_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {
  	struct tegra_rtc_info *info = dev_get_drvdata(dev);
  	unsigned long sec;
  	int ret;
  
  	/* convert tm to seconds. */
  	ret = rtc_valid_tm(tm);
  	if (ret)
  		return ret;
  
  	rtc_tm_to_time(tm, &sec);
  
  	dev_vdbg(dev, "time set to %lu. %d/%d/%d %d:%02u:%02u
  ",
  		sec,
  		tm->tm_mon+1,
  		tm->tm_mday,
  		tm->tm_year+1900,
  		tm->tm_hour,
  		tm->tm_min,
  		tm->tm_sec
  	);
  
  	/* seconds only written if wait succeeded. */
  	ret = tegra_rtc_wait_while_busy(dev);
  	if (!ret)
  		writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS);
  
  	dev_vdbg(dev, "time read back as %d
  ",
  		readl(info->rtc_base + TEGRA_RTC_REG_SECONDS));
  
  	return ret;
  }
  
  static int tegra_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {
  	struct tegra_rtc_info *info = dev_get_drvdata(dev);
  	unsigned long sec;
  	unsigned tmp;
  
  	sec = readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
  
  	if (sec == 0) {
  		/* alarm is disabled. */
  		alarm->enabled = 0;
  		alarm->time.tm_mon = -1;
  		alarm->time.tm_mday = -1;
  		alarm->time.tm_year = -1;
  		alarm->time.tm_hour = -1;
  		alarm->time.tm_min = -1;
  		alarm->time.tm_sec = -1;
  	} else {
  		/* alarm is enabled. */
  		alarm->enabled = 1;
  		rtc_time_to_tm(sec, &alarm->time);
  	}
  
  	tmp = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
  	alarm->pending = (tmp & TEGRA_RTC_INTR_STATUS_SEC_ALARM0) != 0;
  
  	return 0;
  }
  
  static int tegra_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
  {
  	struct tegra_rtc_info *info = dev_get_drvdata(dev);
  	unsigned status;
  	unsigned long sl_irq_flags;
  
  	tegra_rtc_wait_while_busy(dev);
  	spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
  
  	/* read the original value, and OR in the flag. */
  	status = readl(info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
  	if (enabled)
  		status |= TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* set it */
  	else
  		status &= ~TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* clear it */
  
  	writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
  
  	spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
  
  	return 0;
  }
  
  static int tegra_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {
  	struct tegra_rtc_info *info = dev_get_drvdata(dev);
  	unsigned long sec;
  
  	if (alarm->enabled)
  		rtc_tm_to_time(&alarm->time, &sec);
  	else
  		sec = 0;
  
  	tegra_rtc_wait_while_busy(dev);
  	writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
  	dev_vdbg(dev, "alarm read back as %d
  ",
  		readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));
  
  	/* if successfully written and alarm is enabled ... */
  	if (sec) {
  		tegra_rtc_alarm_irq_enable(dev, 1);
  
  		dev_vdbg(dev, "alarm set as %lu. %d/%d/%d %d:%02u:%02u
  ",
  			sec,
  			alarm->time.tm_mon+1,
  			alarm->time.tm_mday,
  			alarm->time.tm_year+1900,
  			alarm->time.tm_hour,
  			alarm->time.tm_min,
  			alarm->time.tm_sec);
  	} else {
  		/* disable alarm if 0 or write error. */
  		dev_vdbg(dev, "alarm disabled
  ");
  		tegra_rtc_alarm_irq_enable(dev, 0);
  	}
  
  	return 0;
  }
  
  static int tegra_rtc_proc(struct device *dev, struct seq_file *seq)
  {
  	if (!dev || !dev->driver)
  		return 0;
  
  	return seq_printf(seq, "name\t\t: %s
  ", dev_name(dev));
  }
  
  static irqreturn_t tegra_rtc_irq_handler(int irq, void *data)
  {
  	struct device *dev = data;
  	struct tegra_rtc_info *info = dev_get_drvdata(dev);
  	unsigned long events = 0;
  	unsigned status;
  	unsigned long sl_irq_flags;
  
  	status = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
  	if (status) {
  		/* clear the interrupt masks and status on any irq. */
  		tegra_rtc_wait_while_busy(dev);
  		spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
  		writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
  		writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
  		spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
  	}
  
  	/* check if Alarm */
  	if ((status & TEGRA_RTC_INTR_STATUS_SEC_ALARM0))
  		events |= RTC_IRQF | RTC_AF;
  
  	/* check if Periodic */
  	if ((status & TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM))
  		events |= RTC_IRQF | RTC_PF;
  
  	rtc_update_irq(info->rtc_dev, 1, events);
  
  	return IRQ_HANDLED;
  }
  
  static struct rtc_class_ops tegra_rtc_ops = {
  	.read_time	= tegra_rtc_read_time,
  	.set_time	= tegra_rtc_set_time,
  	.read_alarm	= tegra_rtc_read_alarm,
  	.set_alarm	= tegra_rtc_set_alarm,
  	.proc		= tegra_rtc_proc,
  	.alarm_irq_enable = tegra_rtc_alarm_irq_enable,
  };
  
  static const struct of_device_id tegra_rtc_dt_match[] = {
  	{ .compatible = "nvidia,tegra20-rtc", },
  	{}
  };
  MODULE_DEVICE_TABLE(of, tegra_rtc_dt_match);
  
  static int __init tegra_rtc_probe(struct platform_device *pdev)
  {
  	struct tegra_rtc_info *info;
  	struct resource *res;
  	int ret;
  
  	info = devm_kzalloc(&pdev->dev, sizeof(struct tegra_rtc_info),
  		GFP_KERNEL);
  	if (!info)
  		return -ENOMEM;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	info->rtc_base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(info->rtc_base))
  		return PTR_ERR(info->rtc_base);
  
  	info->tegra_rtc_irq = platform_get_irq(pdev, 0);
  	if (info->tegra_rtc_irq <= 0)
  		return -EBUSY;
  
  	/* set context info. */
  	info->pdev = pdev;
  	spin_lock_init(&info->tegra_rtc_lock);
  
  	platform_set_drvdata(pdev, info);
  
  	/* clear out the hardware. */
  	writel(0, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
  	writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
  	writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
  
  	device_init_wakeup(&pdev->dev, 1);
  
  	info->rtc_dev = devm_rtc_device_register(&pdev->dev,
  				dev_name(&pdev->dev), &tegra_rtc_ops,
  				THIS_MODULE);
  	if (IS_ERR(info->rtc_dev)) {
  		ret = PTR_ERR(info->rtc_dev);
  		dev_err(&pdev->dev, "Unable to register device (err=%d).
  ",
  			ret);
  		return ret;
  	}
  
  	ret = devm_request_irq(&pdev->dev, info->tegra_rtc_irq,
  			tegra_rtc_irq_handler, IRQF_TRIGGER_HIGH,
  			dev_name(&pdev->dev), &pdev->dev);
  	if (ret) {
  		dev_err(&pdev->dev,
  			"Unable to request interrupt for device (err=%d).
  ",
  			ret);
  		return ret;
  	}
  
  	dev_notice(&pdev->dev, "Tegra internal Real Time Clock
  ");
  
  	return 0;
  }
  
  #ifdef CONFIG_PM_SLEEP
  static int tegra_rtc_suspend(struct device *dev)
  {
  	struct tegra_rtc_info *info = dev_get_drvdata(dev);
  
  	tegra_rtc_wait_while_busy(dev);
  
  	/* only use ALARM0 as a wake source. */
  	writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
  	writel(TEGRA_RTC_INTR_STATUS_SEC_ALARM0,
  		info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
  
  	dev_vdbg(dev, "alarm sec = %d
  ",
  		readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));
  
  	dev_vdbg(dev, "Suspend (device_may_wakeup=%d) irq:%d
  ",
  		device_may_wakeup(dev), info->tegra_rtc_irq);
  
  	/* leave the alarms on as a wake source. */
  	if (device_may_wakeup(dev))
  		enable_irq_wake(info->tegra_rtc_irq);
  
  	return 0;
  }
  
  static int tegra_rtc_resume(struct device *dev)
  {
  	struct tegra_rtc_info *info = dev_get_drvdata(dev);
  
  	dev_vdbg(dev, "Resume (device_may_wakeup=%d)
  ",
  		device_may_wakeup(dev));
  	/* alarms were left on as a wake source, turn them off. */
  	if (device_may_wakeup(dev))
  		disable_irq_wake(info->tegra_rtc_irq);
  
  	return 0;
  }
  #endif
  
  static SIMPLE_DEV_PM_OPS(tegra_rtc_pm_ops, tegra_rtc_suspend, tegra_rtc_resume);
  
  static void tegra_rtc_shutdown(struct platform_device *pdev)
  {
  	dev_vdbg(&pdev->dev, "disabling interrupts.
  ");
  	tegra_rtc_alarm_irq_enable(&pdev->dev, 0);
  }
  
  MODULE_ALIAS("platform:tegra_rtc");
  static struct platform_driver tegra_rtc_driver = {
  	.shutdown	= tegra_rtc_shutdown,
  	.driver		= {
  		.name	= "tegra_rtc",
  		.owner	= THIS_MODULE,
  		.of_match_table = tegra_rtc_dt_match,
  		.pm	= &tegra_rtc_pm_ops,
  	},
  };
  
  module_platform_driver_probe(tegra_rtc_driver, tegra_rtc_probe);
  
  MODULE_AUTHOR("Jon Mayo <jmayo@nvidia.com>");
  MODULE_DESCRIPTION("driver for Tegra internal RTC");
  MODULE_LICENSE("GPL");