/*
   * Copyright (C) ST-Ericsson SA 2011
   *
   * License Terms: GNU General Public License v2
   * Author: Mattias Wallin <mattias.wallin@stericsson.com> for ST-Ericsson
   * Author: Sundar Iyer for ST-Ericsson
   * sched_clock implementation is based on:
   * plat-nomadik/timer.c Linus Walleij <linus.walleij@stericsson.com>
   *
   * DBx500-PRCMU Timer
   * The PRCMU has 5 timers which are available in a always-on
   * power domain.  We use the Timer 4 for our always-on clock

   * source on DB8500.

   */

  #include <linux/of.h>
  #include <linux/of_address.h>

  #include <linux/clockchips.h>

  #include <linux/sched_clock.h>

  #define RATE_32K		32768
  
  #define TIMER_MODE_CONTINOUS	0x1
  #define TIMER_DOWNCOUNT_VAL	0xffffffff
  
  #define PRCMU_TIMER_REF		0
  #define PRCMU_TIMER_DOWNCOUNT	0x4
  #define PRCMU_TIMER_MODE	0x8
  
  #define SCHED_CLOCK_MIN_WRAP 131072 /* 2^32 / 32768 */

  static void __iomem *clksrc_dbx500_timer_base;

  static cycle_t notrace clksrc_dbx500_prcmu_read(struct clocksource *cs)

  {

  	void __iomem *base = clksrc_dbx500_timer_base;

  	u32 count, count2;
  
  	do {

  		count = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
  		count2 = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);

  	} while (count2 != count);
  
  	/* Negate because the timer is a decrementing counter */
  	return ~count;
  }
  
  static struct clocksource clocksource_dbx500_prcmu = {
  	.name		= "dbx500-prcmu-timer",
  	.rating		= 300,
  	.read		= clksrc_dbx500_prcmu_read,

  	.mask		= CLOCKSOURCE_MASK(32),
  	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
  };
  
  #ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK

  static u64 notrace dbx500_prcmu_sched_clock_read(void)

  {

  	if (unlikely(!clksrc_dbx500_timer_base))
  		return 0;

  	return clksrc_dbx500_prcmu_read(&clocksource_dbx500_prcmu);

  }

  #endif

  static int __init clksrc_dbx500_prcmu_init(struct device_node *node)

  {

  	clksrc_dbx500_timer_base = of_iomap(node, 0);

  	/*
  	 * The A9 sub system expects the timer to be configured as
  	 * a continous looping timer.
  	 * The PRCMU should configure it but if it for some reason
  	 * don't we do it here.
  	 */
  	if (readl(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) !=
  	    TIMER_MODE_CONTINOUS) {
  		writel(TIMER_MODE_CONTINOUS,
  		       clksrc_dbx500_timer_base + PRCMU_TIMER_MODE);
  		writel(TIMER_DOWNCOUNT_VAL,
  		       clksrc_dbx500_timer_base + PRCMU_TIMER_REF);
  	}
  #ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK

  	sched_clock_register(dbx500_prcmu_sched_clock_read, 32, RATE_32K);

  #endif

  	return clocksource_register_hz(&clocksource_dbx500_prcmu, RATE_32K);

  }

  CLOCKSOURCE_OF_DECLARE(dbx500_prcmu, "stericsson,db8500-prcmu-timer-4",

  		       clksrc_dbx500_prcmu_init);