arch/mips/kernel/time.c

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

File Facts

System
Linux kernel
Corpus path
arch/mips/kernel/time.c
Extension
.c
Size
4139 bytes
Lines
168
Domain
Architecture Layer
Bucket
arch/mips
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

core_initcall(register_cpufreq_notifier);

#endif /* CONFIG_CPU_FREQ */

/*
 * forward reference
 */
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);

static int null_perf_irq(void)
{
	return 0;
}

int (*perf_irq)(void) = null_perf_irq;

EXPORT_SYMBOL(perf_irq);

/*
 * time_init() - it does the following things.
 *
 * 1) plat_time_init() -
 *	a) (optional) set up RTC routines,
 *	b) (optional) calibrate and set the mips_hpt_frequency
 *	    (only needed if you intended to use cpu counter as timer interrupt
 *	     source)
 * 2) calculate a couple of cached variables for later usage
 */

unsigned int mips_hpt_frequency;
EXPORT_SYMBOL_GPL(mips_hpt_frequency);

static __init int cpu_has_mfc0_count_bug(void)
{
	switch (current_cpu_type()) {
	case CPU_R4000PC:
	case CPU_R4000SC:
	case CPU_R4000MC:
		/*
		 * V3.0 is documented as suffering from the mfc0 from count bug.
		 * Afaik this is the last version of the R4000.	 Later versions
		 * were marketed as R4400.
		 */
		return 1;

	case CPU_R4400PC:
	case CPU_R4400SC:
	case CPU_R4400MC:
		/*
		 * The published errata for the R4400 up to 3.0 say the CPU
		 * has the mfc0 from count bug.  This seems the last version
		 * produced.
		 */
		return 1;
	}

	return 0;
}

void __init time_init(void)
{
	plat_time_init();

	/*
	 * The use of the R4k timer as a clock event takes precedence;
	 * if reading the Count register might interfere with the timer
	 * interrupt, then we don't use the timer as a clock source.
	 * We may still use the timer as a clock source though if the
	 * timer interrupt isn't reliable; the interference doesn't
	 * matter then, because we don't use the interrupt.
	 */
	if (mips_clockevent_init() != 0 || !cpu_has_mfc0_count_bug())
		init_mips_clocksource();
}

Annotation

Implementation Notes