arch/mips/sgi-ip27/ip27-timer.c

Source file repositories/reference/linux-study-clean/arch/mips/sgi-ip27/ip27-timer.c

File Facts

System
Linux kernel
Corpus path
arch/mips/sgi-ip27/ip27-timer.c
Extension
.c
Size
4037 bytes
Lines
155
Domain
Architecture Layer
Bucket
arch/mips
Inferred role
Architecture Layer: implementation source
Status
source 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) 1999, 2000, 05, 06 Ralf Baechle (ralf@linux-mips.org)
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 */
#include <linux/bcd.h>
#include <linux/clockchips.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/sched_clock.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/param.h>
#include <linux/smp.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/mm.h>
#include <linux/platform_device.h>

#include <asm/time.h>
#include <asm/sgialib.h>
#include <asm/sn/klconfig.h>
#include <asm/sn/arch.h>
#include <asm/sn/addrs.h>
#include <asm/sn/agent.h>

#include "ip27-common.h"

static int rt_next_event(unsigned long delta, struct clock_event_device *evt)
{
	unsigned int cpu = smp_processor_id();
	int slice = cputoslice(cpu);
	unsigned long cnt;

	cnt = LOCAL_HUB_L(PI_RT_COUNT);
	cnt += delta;
	LOCAL_HUB_S(PI_RT_COMPARE_A + PI_COUNT_OFFSET * slice, cnt);

	return LOCAL_HUB_L(PI_RT_COUNT) >= cnt ? -ETIME : 0;
}

static DEFINE_PER_CPU(struct clock_event_device, hub_rt_clockevent);
static DEFINE_PER_CPU(char [11], hub_rt_name);

static irqreturn_t hub_rt_counter_handler(int irq, void *dev_id)
{
	unsigned int cpu = smp_processor_id();
	struct clock_event_device *cd = &per_cpu(hub_rt_clockevent, cpu);
	int slice = cputoslice(cpu);

	/*
	 * Ack
	 */
	LOCAL_HUB_S(PI_RT_PEND_A + PI_COUNT_OFFSET * slice, 0);
	cd->event_handler(cd);

	return IRQ_HANDLED;
}

/*
 * This is a hack; we really need to figure these values out dynamically
 *
 * Since 800 ns works very well with various HUB frequencies, such as
 * 360, 380, 390 and 400 MHZ, we use 800 ns rtc cycle time.
 *
 * Ralf: which clock rate is used to feed the counter?
 */
#define NSEC_PER_CYCLE		800
#define CYCLES_PER_SEC		(NSEC_PER_SEC / NSEC_PER_CYCLE)

void hub_rt_clock_event_init(void)
{
	unsigned int cpu = smp_processor_id();
	struct clock_event_device *cd = &per_cpu(hub_rt_clockevent, cpu);
	unsigned char *name = per_cpu(hub_rt_name, cpu);

	sprintf(name, "hub-rt %d", cpu);
	cd->name		= name;
	cd->features		= CLOCK_EVT_FEAT_ONESHOT;
	clockevent_set_clock(cd, CYCLES_PER_SEC);
	cd->max_delta_ns	= clockevent_delta2ns(0xfffffffffffff, cd);
	cd->max_delta_ticks	= 0xfffffffffffff;
	cd->min_delta_ns	= clockevent_delta2ns(0x300, cd);
	cd->min_delta_ticks	= 0x300;
	cd->rating		= 200;
	cd->irq			= IP27_RT_TIMER_IRQ;
	cd->cpumask		= cpumask_of(cpu);
	cd->set_next_event	= rt_next_event;
	clockevents_register_device(cd);

Annotation

Implementation Notes