1. 根目录:
2. arch
3. arm
4. plat-omap
5. 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/clocksource.h>

#include <asm/sched_clock.h>

#include <plat/hardware.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.
 */
static void __iomem *timer_32k_base;

#define OMAP16XX_TIMER_32K_SYNCHRONIZED		0xfffbc410

static u32 notrace omap_32k_read_sched_clock(void)
{
	return timer_32k_base ? __raw_readl(timer_32k_base) : 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;
static unsigned int persistent_mult, persistent_shift;
static DEFINE_SPINLOCK(read_persistent_clock_lock);

void read_persistent_clock(struct timespec *ts)
{
	unsigned long long nsecs;
	cycles_t last_cycles;
	unsigned long flags;

	spin_lock_irqsave(&read_persistent_clock_lock, flags);

	last_cycles = cycles;
	cycles = timer_32k_base ? __raw_readl(timer_32k_base) : 0;

	nsecs = clocksource_cyc2ns(cycles - last_cycles,
					persistent_mult, persistent_shift);

	timespec_add_ns(&persistent_ts, nsecs);

	*ts = persistent_ts;

	spin_unlock_irqrestore(&read_persistent_clock_lock, flags);
}

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()) {
		u32 pbase;
		unsigned long size = SZ_4K;
		void __iomem *base;
		struct clk *sync_32k_ick;

		if (cpu_is_omap16xx()) {
			pbase = OMAP16XX_TIMER_32K_SYNCHRONIZED;
			size = SZ_1K;
		} else if (cpu_is_omap2420())
			pbase = OMAP2420_32KSYNCT_BASE + 0x10;
		else if (cpu_is_omap2430())
			pbase = OMAP2430_32KSYNCT_BASE + 0x10;
		else if (cpu_is_omap34xx())
			pbase = OMAP3430_32KSYNCT_BASE + 0x10;
		else if (cpu_is_omap44xx())
			pbase = OMAP4430_32KSYNCT_BASE + 0x10;
		else
			return -ENODEV;

		/* For this to work we must have a static mapping in io.c for this area */
		base = ioremap(pbase, size);
		if (!base)
			return -ENODEV;

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

		timer_32k_base = base;

		/*
		 * 120000 rough estimate from the calculations in
		 * __clocksource_updatefreq_scale.
		 */
		clocks_calc_mult_shift(&persistent_mult, &persistent_shift,
				32768, NSEC_PER_SEC, 120000);

		if (clocksource_mmio_init(base, "32k_counter", 32768, 250, 32,
					  clocksource_mmio_readl_up))
			printk(err, "32k_counter");

		setup_sched_clock(omap_32k_read_sched_clock, 32, 32768);
	}
	return 0;
}