arch/arm/kernel/time.c

root/arch/arm/kernel/time.c
// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/arch/arm/kernel/time.c
 *
 *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
 *  Modifications for ARM (C) 1994-2001 Russell King
 *
 *  This file contains the ARM-specific time handling details:
 *  reading the RTC at bootup, etc...
 */
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/of_clk.h>
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/sched_clock.h>
#include <linux/smp.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/timer.h>

#include <asm/mach/arch.h>
#include <asm/mach/time.h>
#include <asm/stacktrace.h>
#include <asm/thread_info.h>

#if defined(CONFIG_RTC_DRV_CMOS) || defined(CONFIG_RTC_DRV_CMOS_MODULE) || \
    defined(CONFIG_NVRAM) || defined(CONFIG_NVRAM_MODULE)
/* this needs a better home */
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
#endif  /* pc-style 'CMOS' RTC support */

/* change this if you have some constant time drift */
#define USECS_PER_JIFFY (1000000/HZ)

#ifdef CONFIG_SMP
unsigned long profile_pc(struct pt_regs *regs)
{
        struct stackframe frame;

        if (!in_lock_functions(regs->ARM_pc))
                return regs->ARM_pc;

        arm_get_current_stackframe(regs, &frame);
        do {
                int ret = unwind_frame(&frame);
                if (ret < 0)
                        return 0;
        } while (in_lock_functions(frame.pc));

        return frame.pc;
}
EXPORT_SYMBOL(profile_pc);
#endif

static void dummy_clock_access(struct timespec64 *ts)
{
        ts->tv_sec = 0;
        ts->tv_nsec = 0;
}

static clock_access_fn __read_persistent_clock = dummy_clock_access;

void read_persistent_clock64(struct timespec64 *ts)
{
        __read_persistent_clock(ts);
}

int __init register_persistent_clock(clock_access_fn read_persistent)
{
        /* Only allow the clockaccess functions to be registered once */
        if (__read_persistent_clock == dummy_clock_access) {
                if (read_persistent)
                        __read_persistent_clock = read_persistent;
                return 0;
        }

        return -EINVAL;
}

void __init time_init(void)
{
        if (machine_desc->init_time) {
                machine_desc->init_time();
        } else {
#ifdef CONFIG_COMMON_CLK
                of_clk_init(NULL);
#endif
                timer_probe();
                tick_setup_hrtimer_broadcast();
        }
}
Linux
