/*
   * rtc-mrst.c: Driver for Moorestown virtual RTC
   *
   * (C) Copyright 2009 Intel Corporation
   * Author: Jacob Pan (jacob.jun.pan@intel.com)
   *	   Feng Tang (feng.tang@intel.com)
   *
   * 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; version 2
   * of the License.
   *
   * Note:
   * VRTC is emulated by system controller firmware, the real HW
   * RTC is located in the PMIC device. SCU FW shadows PMIC RTC
   * in a memory mapped IO space that is visible to the host IA
   * processor.
   *
   * This driver is based upon drivers/rtc/rtc-cmos.c
   */
  
  /*
   * Note:
   *  * vRTC only supports binary mode and 24H mode
   *  * vRTC only support PIE and AIE, no UIE, and its PIE only happens
   *    at 23:59:59pm everyday, no support for adjustable frequency
   *  * Alarm function is also limited to hr/min/sec.
   */
  
  #include <linux/mod_devicetable.h>
  #include <linux/platform_device.h>
  #include <linux/interrupt.h>
  #include <linux/spinlock.h>
  #include <linux/kernel.h>

  #include <linux/mc146818rtc.h>

  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/sfi.h>

  #include <asm/intel_scu_ipc.h>

  #include <asm/intel-mid.h>
  #include <asm/intel_mid_vrtc.h>

  
  struct mrst_rtc {
  	struct rtc_device	*rtc;
  	struct device		*dev;
  	int			irq;
  	struct resource		*iomem;
  
  	u8			enabled_wake;
  	u8			suspend_ctrl;
  };
  
  static const char driver_name[] = "rtc_mrst";
  
  #define	RTC_IRQMASK	(RTC_PF | RTC_AF)
  
  static inline int is_intr(u8 rtc_intr)
  {
  	if (!(rtc_intr & RTC_IRQF))
  		return 0;
  	return rtc_intr & RTC_IRQMASK;
  }

  static inline unsigned char vrtc_is_updating(void)
  {
  	unsigned char uip;
  	unsigned long flags;
  
  	spin_lock_irqsave(&rtc_lock, flags);
  	uip = (vrtc_cmos_read(RTC_FREQ_SELECT) & RTC_UIP);
  	spin_unlock_irqrestore(&rtc_lock, flags);
  	return uip;
  }

  /*
   * rtc_time's year contains the increment over 1900, but vRTC's YEAR
   * register can't be programmed to value larger than 0x64, so vRTC

   * driver chose to use 1972 (1970 is UNIX time start point) as the base,

   * and does the translation at read/write time.
   *

   * Why not just use 1970 as the offset? it's because using 1972 will

   * make it consistent in leap year setting for both vrtc and low-level

   * physical rtc devices. Then why not use 1960 as the offset? If we use
   * 1960, for a device's first use, its YEAR register is 0 and the system
   * year will be parsed as 1960 which is not a valid UNIX time and will
   * cause many applications to fail mysteriously.

   */
  static int mrst_read_time(struct device *dev, struct rtc_time *time)
  {
  	unsigned long flags;

  	if (vrtc_is_updating())

  		mdelay(20);
  
  	spin_lock_irqsave(&rtc_lock, flags);
  	time->tm_sec = vrtc_cmos_read(RTC_SECONDS);
  	time->tm_min = vrtc_cmos_read(RTC_MINUTES);
  	time->tm_hour = vrtc_cmos_read(RTC_HOURS);
  	time->tm_mday = vrtc_cmos_read(RTC_DAY_OF_MONTH);
  	time->tm_mon = vrtc_cmos_read(RTC_MONTH);
  	time->tm_year = vrtc_cmos_read(RTC_YEAR);
  	spin_unlock_irqrestore(&rtc_lock, flags);

  	/* Adjust for the 1972/1900 */
  	time->tm_year += 72;

  	time->tm_mon--;

  	return rtc_valid_tm(time);

  }
  
  static int mrst_set_time(struct device *dev, struct rtc_time *time)
  {
  	int ret;
  	unsigned long flags;
  	unsigned char mon, day, hrs, min, sec;
  	unsigned int yrs;
  
  	yrs = time->tm_year;
  	mon = time->tm_mon + 1;   /* tm_mon starts at zero */
  	day = time->tm_mday;
  	hrs = time->tm_hour;
  	min = time->tm_min;
  	sec = time->tm_sec;

  	if (yrs < 72 || yrs > 138)

  		return -EINVAL;

  	yrs -= 72;

  
  	spin_lock_irqsave(&rtc_lock, flags);
  
  	vrtc_cmos_write(yrs, RTC_YEAR);
  	vrtc_cmos_write(mon, RTC_MONTH);
  	vrtc_cmos_write(day, RTC_DAY_OF_MONTH);
  	vrtc_cmos_write(hrs, RTC_HOURS);
  	vrtc_cmos_write(min, RTC_MINUTES);
  	vrtc_cmos_write(sec, RTC_SECONDS);
  
  	spin_unlock_irqrestore(&rtc_lock, flags);
  
  	ret = intel_scu_ipc_simple_command(IPCMSG_VRTC, IPC_CMD_VRTC_SETTIME);
  	return ret;
  }
  
  static int mrst_read_alarm(struct device *dev, struct rtc_wkalrm *t)
  {
  	struct mrst_rtc	*mrst = dev_get_drvdata(dev);
  	unsigned char rtc_control;
  
  	if (mrst->irq <= 0)
  		return -EIO;

  	/* vRTC only supports binary mode */
  	spin_lock_irq(&rtc_lock);
  	t->time.tm_sec = vrtc_cmos_read(RTC_SECONDS_ALARM);
  	t->time.tm_min = vrtc_cmos_read(RTC_MINUTES_ALARM);
  	t->time.tm_hour = vrtc_cmos_read(RTC_HOURS_ALARM);
  
  	rtc_control = vrtc_cmos_read(RTC_CONTROL);
  	spin_unlock_irq(&rtc_lock);
  
  	t->enabled = !!(rtc_control & RTC_AIE);
  	t->pending = 0;
  
  	return 0;
  }
  
  static void mrst_checkintr(struct mrst_rtc *mrst, unsigned char rtc_control)
  {
  	unsigned char	rtc_intr;
  
  	/*
  	 * NOTE after changing RTC_xIE bits we always read INTR_FLAGS;
  	 * allegedly some older rtcs need that to handle irqs properly
  	 */
  	rtc_intr = vrtc_cmos_read(RTC_INTR_FLAGS);
  	rtc_intr &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
  	if (is_intr(rtc_intr))
  		rtc_update_irq(mrst->rtc, 1, rtc_intr);
  }
  
  static void mrst_irq_enable(struct mrst_rtc *mrst, unsigned char mask)
  {
  	unsigned char	rtc_control;
  
  	/*
  	 * Flush any pending IRQ status, notably for update irqs,
  	 * before we enable new IRQs
  	 */
  	rtc_control = vrtc_cmos_read(RTC_CONTROL);
  	mrst_checkintr(mrst, rtc_control);
  
  	rtc_control |= mask;
  	vrtc_cmos_write(rtc_control, RTC_CONTROL);
  
  	mrst_checkintr(mrst, rtc_control);
  }
  
  static void mrst_irq_disable(struct mrst_rtc *mrst, unsigned char mask)
  {
  	unsigned char	rtc_control;
  
  	rtc_control = vrtc_cmos_read(RTC_CONTROL);
  	rtc_control &= ~mask;
  	vrtc_cmos_write(rtc_control, RTC_CONTROL);
  	mrst_checkintr(mrst, rtc_control);
  }
  
  static int mrst_set_alarm(struct device *dev, struct rtc_wkalrm *t)
  {
  	struct mrst_rtc	*mrst = dev_get_drvdata(dev);
  	unsigned char hrs, min, sec;
  	int ret = 0;
  
  	if (!mrst->irq)
  		return -EIO;
  
  	hrs = t->time.tm_hour;
  	min = t->time.tm_min;
  	sec = t->time.tm_sec;
  
  	spin_lock_irq(&rtc_lock);
  	/* Next rtc irq must not be from previous alarm setting */
  	mrst_irq_disable(mrst, RTC_AIE);
  
  	/* Update alarm */
  	vrtc_cmos_write(hrs, RTC_HOURS_ALARM);
  	vrtc_cmos_write(min, RTC_MINUTES_ALARM);
  	vrtc_cmos_write(sec, RTC_SECONDS_ALARM);
  
  	spin_unlock_irq(&rtc_lock);
  
  	ret = intel_scu_ipc_simple_command(IPCMSG_VRTC, IPC_CMD_VRTC_SETALARM);
  	if (ret)
  		return ret;
  
  	spin_lock_irq(&rtc_lock);
  	if (t->enabled)
  		mrst_irq_enable(mrst, RTC_AIE);
  
  	spin_unlock_irq(&rtc_lock);
  
  	return 0;
  }

  /* Currently, the vRTC doesn't support UIE ON/OFF */

  static int mrst_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)

  {
  	struct mrst_rtc	*mrst = dev_get_drvdata(dev);
  	unsigned long	flags;

  	spin_lock_irqsave(&rtc_lock, flags);

  	if (enabled)

  		mrst_irq_enable(mrst, RTC_AIE);

  	else
  		mrst_irq_disable(mrst, RTC_AIE);

  	spin_unlock_irqrestore(&rtc_lock, flags);
  	return 0;
  }

  #if IS_ENABLED(CONFIG_RTC_INTF_PROC)

  
  static int mrst_procfs(struct device *dev, struct seq_file *seq)
  {
  	unsigned char	rtc_control, valid;
  
  	spin_lock_irq(&rtc_lock);
  	rtc_control = vrtc_cmos_read(RTC_CONTROL);
  	valid = vrtc_cmos_read(RTC_VALID);
  	spin_unlock_irq(&rtc_lock);

  	seq_printf(seq,
  		   "periodic_IRQ\t: %s
  "
  		   "alarm\t\t: %s
  "
  		   "BCD\t\t: no
  "
  		   "periodic_freq\t: daily (not adjustable)
  ",
  		   (rtc_control & RTC_PIE) ? "on" : "off",
  		   (rtc_control & RTC_AIE) ? "on" : "off");
  
  	return 0;

  }
  
  #else
  #define	mrst_procfs	NULL
  #endif
  
  static const struct rtc_class_ops mrst_rtc_ops = {

  	.read_time	= mrst_read_time,
  	.set_time	= mrst_set_time,
  	.read_alarm	= mrst_read_alarm,
  	.set_alarm	= mrst_set_alarm,
  	.proc		= mrst_procfs,

  	.alarm_irq_enable = mrst_rtc_alarm_irq_enable,

  };
  
  static struct mrst_rtc	mrst_rtc;
  
  /*
   * When vRTC IRQ is captured by SCU FW, FW will clear the AIE bit in
   * Reg B, so no need for this driver to clear it
   */
  static irqreturn_t mrst_rtc_irq(int irq, void *p)
  {
  	u8 irqstat;
  
  	spin_lock(&rtc_lock);
  	/* This read will clear all IRQ flags inside Reg C */
  	irqstat = vrtc_cmos_read(RTC_INTR_FLAGS);
  	spin_unlock(&rtc_lock);
  
  	irqstat &= RTC_IRQMASK | RTC_IRQF;
  	if (is_intr(irqstat)) {
  		rtc_update_irq(p, 1, irqstat);
  		return IRQ_HANDLED;
  	}
  	return IRQ_NONE;
  }

  static int vrtc_mrst_do_probe(struct device *dev, struct resource *iomem,
  			      int rtc_irq)

  {
  	int retval = 0;
  	unsigned char rtc_control;
  
  	/* There can be only one ... */
  	if (mrst_rtc.dev)
  		return -EBUSY;
  
  	if (!iomem)
  		return -ENODEV;

  	iomem = request_mem_region(iomem->start, resource_size(iomem),
  				   driver_name);

  	if (!iomem) {
  		dev_dbg(dev, "i/o mem already in use.
  ");
  		return -EBUSY;
  	}
  
  	mrst_rtc.irq = rtc_irq;
  	mrst_rtc.iomem = iomem;

  	mrst_rtc.dev = dev;
  	dev_set_drvdata(dev, &mrst_rtc);

  
  	mrst_rtc.rtc = rtc_device_register(driver_name, dev,
  				&mrst_rtc_ops, THIS_MODULE);
  	if (IS_ERR(mrst_rtc.rtc)) {
  		retval = PTR_ERR(mrst_rtc.rtc);
  		goto cleanup0;
  	}

  	rename_region(iomem, dev_name(&mrst_rtc.rtc->dev));
  
  	spin_lock_irq(&rtc_lock);
  	mrst_irq_disable(&mrst_rtc, RTC_PIE | RTC_AIE);
  	rtc_control = vrtc_cmos_read(RTC_CONTROL);
  	spin_unlock_irq(&rtc_lock);
  
  	if (!(rtc_control & RTC_24H) || (rtc_control & (RTC_DM_BINARY)))
  		dev_dbg(dev, "TODO: support more than 24-hr BCD mode
  ");
  
  	if (rtc_irq) {
  		retval = request_irq(rtc_irq, mrst_rtc_irq,

  				0, dev_name(&mrst_rtc.rtc->dev),

  				mrst_rtc.rtc);
  		if (retval < 0) {
  			dev_dbg(dev, "IRQ %d is already in use, err %d
  ",
  				rtc_irq, retval);
  			goto cleanup1;
  		}
  	}
  	dev_dbg(dev, "initialised
  ");
  	return 0;
  
  cleanup1:

  	rtc_device_unregister(mrst_rtc.rtc);
  cleanup0:

  	mrst_rtc.dev = NULL;

  	release_mem_region(iomem->start, resource_size(iomem));

  	dev_err(dev, "rtc-mrst: unable to initialise
  ");
  	return retval;
  }
  
  static void rtc_mrst_do_shutdown(void)
  {
  	spin_lock_irq(&rtc_lock);
  	mrst_irq_disable(&mrst_rtc, RTC_IRQMASK);
  	spin_unlock_irq(&rtc_lock);
  }

  static void rtc_mrst_do_remove(struct device *dev)

  {
  	struct mrst_rtc	*mrst = dev_get_drvdata(dev);
  	struct resource *iomem;
  
  	rtc_mrst_do_shutdown();
  
  	if (mrst->irq)
  		free_irq(mrst->irq, mrst->rtc);
  
  	rtc_device_unregister(mrst->rtc);
  	mrst->rtc = NULL;
  
  	iomem = mrst->iomem;

  	release_mem_region(iomem->start, resource_size(iomem));

  	mrst->iomem = NULL;
  
  	mrst->dev = NULL;

  }

  #ifdef CONFIG_PM_SLEEP
  static int mrst_suspend(struct device *dev)

  {
  	struct mrst_rtc	*mrst = dev_get_drvdata(dev);
  	unsigned char	tmp;
  
  	/* Only the alarm might be a wakeup event source */
  	spin_lock_irq(&rtc_lock);
  	mrst->suspend_ctrl = tmp = vrtc_cmos_read(RTC_CONTROL);
  	if (tmp & (RTC_PIE | RTC_AIE)) {
  		unsigned char	mask;
  
  		if (device_may_wakeup(dev))
  			mask = RTC_IRQMASK & ~RTC_AIE;
  		else
  			mask = RTC_IRQMASK;
  		tmp &= ~mask;
  		vrtc_cmos_write(tmp, RTC_CONTROL);
  
  		mrst_checkintr(mrst, tmp);
  	}
  	spin_unlock_irq(&rtc_lock);
  
  	if (tmp & RTC_AIE) {
  		mrst->enabled_wake = 1;
  		enable_irq_wake(mrst->irq);
  	}
  
  	dev_dbg(&mrst_rtc.rtc->dev, "suspend%s, ctrl %02x
  ",
  			(tmp & RTC_AIE) ? ", alarm may wake" : "",
  			tmp);
  
  	return 0;
  }
  
  /*
   * We want RTC alarms to wake us from the deep power saving state
   */
  static inline int mrst_poweroff(struct device *dev)
  {

  	return mrst_suspend(dev);

  }
  
  static int mrst_resume(struct device *dev)
  {
  	struct mrst_rtc	*mrst = dev_get_drvdata(dev);
  	unsigned char tmp = mrst->suspend_ctrl;
  
  	/* Re-enable any irqs previously active */
  	if (tmp & RTC_IRQMASK) {
  		unsigned char	mask;
  
  		if (mrst->enabled_wake) {
  			disable_irq_wake(mrst->irq);
  			mrst->enabled_wake = 0;
  		}
  
  		spin_lock_irq(&rtc_lock);
  		do {
  			vrtc_cmos_write(tmp, RTC_CONTROL);
  
  			mask = vrtc_cmos_read(RTC_INTR_FLAGS);
  			mask &= (tmp & RTC_IRQMASK) | RTC_IRQF;
  			if (!is_intr(mask))
  				break;
  
  			rtc_update_irq(mrst->rtc, 1, mask);
  			tmp &= ~RTC_AIE;
  		} while (mask & RTC_AIE);
  		spin_unlock_irq(&rtc_lock);
  	}
  
  	dev_dbg(&mrst_rtc.rtc->dev, "resume, ctrl %02x
  ", tmp);
  
  	return 0;
  }

  static SIMPLE_DEV_PM_OPS(mrst_pm_ops, mrst_suspend, mrst_resume);
  #define MRST_PM_OPS (&mrst_pm_ops)

  #else

  #define MRST_PM_OPS NULL

  
  static inline int mrst_poweroff(struct device *dev)
  {
  	return -ENOSYS;
  }
  
  #endif

  static int vrtc_mrst_platform_probe(struct platform_device *pdev)

  {
  	return vrtc_mrst_do_probe(&pdev->dev,
  			platform_get_resource(pdev, IORESOURCE_MEM, 0),
  			platform_get_irq(pdev, 0));
  }

  static int vrtc_mrst_platform_remove(struct platform_device *pdev)

  {
  	rtc_mrst_do_remove(&pdev->dev);
  	return 0;
  }
  
  static void vrtc_mrst_platform_shutdown(struct platform_device *pdev)
  {
  	if (system_state == SYSTEM_POWER_OFF && !mrst_poweroff(&pdev->dev))
  		return;
  
  	rtc_mrst_do_shutdown();
  }
  
  MODULE_ALIAS("platform:vrtc_mrst");
  
  static struct platform_driver vrtc_mrst_platform_driver = {
  	.probe		= vrtc_mrst_platform_probe,

  	.remove		= vrtc_mrst_platform_remove,

  	.shutdown	= vrtc_mrst_platform_shutdown,
  	.driver = {

  		.name	= driver_name,
  		.pm	= MRST_PM_OPS,

  	}
  };

  module_platform_driver(vrtc_mrst_platform_driver);

  
  MODULE_AUTHOR("Jacob Pan; Feng Tang");
  MODULE_DESCRIPTION("Driver for Moorestown virtual RTC");
  MODULE_LICENSE("GPL");