/* *  linux/arch/arm/kernel/time.c * *  Copyright (C) 1991, 1992, 1995  Linus Torvalds *  Modifications for ARM (C) 1994-2001 Russell King * * 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. * *  This file contains the ARM-specific time handling details: *  reading the RTC at bootup, etc... */#include <linux/clk-provider.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/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_SMPunsigned 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 #ifndef CONFIG_GENERIC_CLOCKEVENTS/* * Kernel system timer support. */void timer_tick(void){	profile_tick(CPU_PROFILING);	xtime_update(1);#ifndef CONFIG_SMP	update_process_times(user_mode(get_irq_regs()));#endif}#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;static clock_access_fn __read_boot_clock = dummy_clock_access;; void read_persistent_clock64(struct timespec64 *ts){	__read_persistent_clock(ts);} void read_boot_clock64(struct timespec64 *ts){	__read_boot_clock(ts);} int __init register_persistent_clock(clock_access_fn read_boot,				     clock_access_fn read_persistent){	/* Only allow the clockaccess functions to be registered once */	if (__read_persistent_clock == dummy_clock_access &&	    __read_boot_clock == dummy_clock_access) {		if (read_boot)			__read_boot_clock = read_boot;		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();	}}