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/*
* 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 <linux/sched_clock.h>
#include <asm/mach/time.h>
#include <plat/counter-32k.h>
/* OMAP2_32KSYNCNT_CR_OFF: offset of 32ksync counter register */
#define OMAP2_32KSYNCNT_REV_OFF 0x0
#define OMAP2_32KSYNCNT_REV_SCHEME (0x3 << 30)
#define OMAP2_32KSYNCNT_CR_OFF_LOW 0x10
#define OMAP2_32KSYNCNT_CR_OFF_HIGH 0x30
/*
* 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 *sync32k_cnt_reg;
static u64 notrace omap_32k_read_sched_clock(void)
{
return sync32k_cnt_reg ? readl_relaxed(sync32k_cnt_reg) : 0;
}
/**
* omap_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);
static void omap_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 = sync32k_cnt_reg ? readl_relaxed(sync32k_cnt_reg) : 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);
}
/**
* omap_init_clocksource_32k - setup and register counter 32k as a
* kernel clocksource
* @pbase: base addr of counter_32k module
* @size: size of counter_32k to map
*
* Returns 0 upon success or negative error code upon failure.
*
*/
int __init omap_init_clocksource_32k(void __iomem *vbase)
{
int ret;
/*
* 32k sync Counter IP register offsets vary between the
* highlander version and the legacy ones.
* The 'SCHEME' bits(30-31) of the revision register is used
* to identify the version.
*/
if (readl_relaxed(vbase + OMAP2_32KSYNCNT_REV_OFF) &
OMAP2_32KSYNCNT_REV_SCHEME)
sync32k_cnt_reg = vbase + OMAP2_32KSYNCNT_CR_OFF_HIGH;
else
sync32k_cnt_reg = vbase + OMAP2_32KSYNCNT_CR_OFF_LOW;
/*
* 120000 rough estimate from the calculations in
* __clocksource_updatefreq_scale.
*/
clocks_calc_mult_shift(&persistent_mult, &persistent_shift,
32768, NSEC_PER_SEC, 120000);
ret = clocksource_mmio_init(sync32k_cnt_reg, "32k_counter", 32768,
250, 32, clocksource_mmio_readl_up);
if (ret) {
pr_err("32k_counter: can't register clocksource\n");
return ret;
}
sched_clock_register(omap_32k_read_sched_clock, 32, 32768);
register_persistent_clock(NULL, omap_read_persistent_clock);
pr_info("OMAP clocksource: 32k_counter at 32768 Hz\n");
return 0;
}
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