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counter_32k.c

/*
 * OMAP 32ksynctimer/counter_32k-related code
 *
 * Copyright (C) 2009 Texas Instruments
 * Copyright (C) 2010 Nokia Corporation
 * Tony Lindgren <tony@atomide.com>
 * Added OMAP4 support - Santosh Shilimkar <santosh.shilimkar@ti.com>
 *
 * 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.
 *
 * NOTE: This timer is not the same timer as the old OMAP1 MPU timer.
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/sched.h>

#include <asm/sched_clock.h>

#include <plat/common.h>
#include <plat/board.h>

#include <plat/clock.h>


/*
 * 32KHz clocksource ... always available, on pretty most chips except
 * OMAP 730 and 1510.  Other timers could be used as clocksources, with
 * higher resolution in free-running counter modes (e.g. 12 MHz xtal),
 * but systems won't necessarily want to spend resources that way.
 */

#define OMAP16XX_TIMER_32K_SYNCHRONIZED         0xfffbc410

#include <linux/clocksource.h>

/*
 * offset_32k holds the init time counter value. It is then subtracted
 * from every counter read to achieve a counter that counts time from the
 * kernel boot (needed for sched_clock()).
 */
static u32 offset_32k __read_mostly;

#ifdef CONFIG_ARCH_OMAP16XX
static cycle_t notrace omap16xx_32k_read(struct clocksource *cs)
{
      return omap_readl(OMAP16XX_TIMER_32K_SYNCHRONIZED) - offset_32k;
}
#else
#define omap16xx_32k_read     NULL
#endif

#ifdef CONFIG_ARCH_OMAP2420
static cycle_t notrace omap2420_32k_read(struct clocksource *cs)
{
      return omap_readl(OMAP2420_32KSYNCT_BASE + 0x10) - offset_32k;
}
#else
#define omap2420_32k_read     NULL
#endif

#ifdef CONFIG_ARCH_OMAP2430
static cycle_t notrace omap2430_32k_read(struct clocksource *cs)
{
      return omap_readl(OMAP2430_32KSYNCT_BASE + 0x10) - offset_32k;
}
#else
#define omap2430_32k_read     NULL
#endif

#ifdef CONFIG_ARCH_OMAP3
static cycle_t notrace omap34xx_32k_read(struct clocksource *cs)
{
      return omap_readl(OMAP3430_32KSYNCT_BASE + 0x10) - offset_32k;
}
#else
#define omap34xx_32k_read     NULL
#endif

#ifdef CONFIG_ARCH_OMAP4
static cycle_t notrace omap44xx_32k_read(struct clocksource *cs)
{
      return omap_readl(OMAP4430_32KSYNCT_BASE + 0x10) - offset_32k;
}
#else
#define omap44xx_32k_read     NULL
#endif

/*
 * Kernel assumes that sched_clock can be called early but may not have
 * things ready yet.
 */
static cycle_t notrace omap_32k_read_dummy(struct clocksource *cs)
{
      return 0;
}

static struct clocksource clocksource_32k = {
      .name       = "32k_counter",
      .rating           = 250,
      .read       = omap_32k_read_dummy,
      .mask       = CLOCKSOURCE_MASK(32),
      .flags            = CLOCK_SOURCE_IS_CONTINUOUS,
};

/*
 * Returns current time from boot in nsecs. It's OK for this to wrap
 * around for now, as it's just a relative time stamp.
 */
static DEFINE_CLOCK_DATA(cd);

/*
 * Constants generated by clocks_calc_mult_shift(m, s, 32768, NSEC_PER_SEC, 60).
 * This gives a resolution of about 30us and a wrap period of about 36hrs.
 */
#define SC_MULT         4000000000u
#define SC_SHIFT  17

static inline unsigned long long notrace _omap_32k_sched_clock(void)
{
      u32 cyc = clocksource_32k.read(&clocksource_32k);
      return cyc_to_fixed_sched_clock(&cd, cyc, (u32)~0, SC_MULT, SC_SHIFT);
}

#ifndef CONFIG_OMAP_MPU_TIMER
unsigned long long notrace sched_clock(void)
{
      return _omap_32k_sched_clock();
}
#else
unsigned long long notrace omap_32k_sched_clock(void)
{
      return _omap_32k_sched_clock();
}
#endif

static void notrace omap_update_sched_clock(void)
{
      u32 cyc = clocksource_32k.read(&clocksource_32k);
      update_sched_clock(&cd, cyc, (u32)~0);
}

/**
 * read_persistent_clock -  Return time from a persistent clock.
 *
 * Reads the time from a source which isn't disabled during PM, the
 * 32k sync timer.  Convert the cycles elapsed since last read into
 * nsecs and adds to a monotonically increasing timespec.
 */
static struct timespec persistent_ts;
static cycles_t cycles, last_cycles;
void read_persistent_clock(struct timespec *ts)
{
      unsigned long long nsecs;
      cycles_t delta;
      struct timespec *tsp = &persistent_ts;

      last_cycles = cycles;
      cycles = clocksource_32k.read(&clocksource_32k);
      delta = cycles - last_cycles;

      nsecs = clocksource_cyc2ns(delta,
                           clocksource_32k.mult, clocksource_32k.shift);

      timespec_add_ns(tsp, nsecs);
      *ts = *tsp;
}

int __init omap_init_clocksource_32k(void)
{
      static char err[] __initdata = KERN_ERR
                  "%s: can't register clocksource!\n";

      if (cpu_is_omap16xx() || cpu_class_is_omap2()) {
            struct clk *sync_32k_ick;

            if (cpu_is_omap16xx())
                  clocksource_32k.read = omap16xx_32k_read;
            else if (cpu_is_omap2420())
                  clocksource_32k.read = omap2420_32k_read;
            else if (cpu_is_omap2430())
                  clocksource_32k.read = omap2430_32k_read;
            else if (cpu_is_omap34xx())
                  clocksource_32k.read = omap34xx_32k_read;
            else if (cpu_is_omap44xx())
                  clocksource_32k.read = omap44xx_32k_read;
            else
                  return -ENODEV;

            sync_32k_ick = clk_get(NULL, "omap_32ksync_ick");
            if (!IS_ERR(sync_32k_ick))
                  clk_enable(sync_32k_ick);

            offset_32k = clocksource_32k.read(&clocksource_32k);

            if (clocksource_register_hz(&clocksource_32k, 32768))
                  printk(err, clocksource_32k.name);

            init_fixed_sched_clock(&cd, omap_update_sched_clock, 32,
                               32768, SC_MULT, SC_SHIFT);
      }
      return 0;
}

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