arch/x86/kernel/time.c

Source file repositories/reference/linux-study-clean/arch/x86/kernel/time.c

File Facts

System
Linux kernel
Corpus path
arch/x86/kernel/time.c
Extension
.c
Size
2597 bytes
Lines
112
Domain
Architecture Layer
Bucket
arch/x86
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (c) 1991,1992,1995  Linus Torvalds
 *  Copyright (c) 1994  Alan Modra
 *  Copyright (c) 1995  Markus Kuhn
 *  Copyright (c) 1996  Ingo Molnar
 *  Copyright (c) 1998  Andrea Arcangeli
 *  Copyright (c) 2002,2006  Vojtech Pavlik
 *  Copyright (c) 2003  Andi Kleen
 *
 */

#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/i8253.h>
#include <linux/time.h>
#include <linux/export.h>

#include <asm/vsyscall.h>
#include <asm/x86_init.h>
#include <asm/i8259.h>
#include <asm/timer.h>
#include <asm/hpet.h>
#include <asm/time.h>

unsigned long profile_pc(struct pt_regs *regs)
{
	return instruction_pointer(regs);
}
EXPORT_SYMBOL(profile_pc);

/*
 * Default timer interrupt handler for PIT/HPET
 */
static irqreturn_t timer_interrupt(int irq, void *dev_id)
{
	global_clock_event->event_handler(global_clock_event);
	return IRQ_HANDLED;
}

static void __init setup_default_timer_irq(void)
{
	unsigned long flags = IRQF_NOBALANCING | IRQF_IRQPOLL | IRQF_TIMER;

	/*
	 * Unconditionally register the legacy timer interrupt; even
	 * without legacy PIC/PIT we need this for the HPET0 in legacy
	 * replacement mode.
	 */
	if (request_irq(0, timer_interrupt, flags, "timer", NULL))
		pr_info("Failed to register legacy timer interrupt\n");
}

/* Default timer init function */
void __init hpet_time_init(void)
{
	if (!hpet_enable()) {
		if (!pit_timer_init())
			return;
	}

	setup_default_timer_irq();
}

static __init void x86_late_time_init(void)
{
	/*
	 * Before PIT/HPET init, select the interrupt mode. This is required
	 * to make the decision whether PIT should be initialized correct.
	 */
	x86_init.irqs.intr_mode_select();

	/* Setup the legacy timers */
	x86_init.timers.timer_init();

	/*
	 * After PIT/HPET timers init, set up the final interrupt mode for
	 * delivering IRQs.
	 */
	x86_init.irqs.intr_mode_init();
	tsc_init();

	if (static_cpu_has(X86_FEATURE_WAITPKG))
		use_tpause_delay();
}

/*
 * Initialize TSC and delay the periodic timer init to

Annotation

Implementation Notes