cregit-Linux how code gets into the kernel

Release 4.8 arch/xtensa/kernel/time.c

/*
 * arch/xtensa/kernel/time.c
 *
 * Timer and clock support.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2005 Tensilica Inc.
 *
 * Chris Zankel <chris@zankel.net>
 */

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/profile.h>
#include <linux/delay.h>
#include <linux/irqdomain.h>
#include <linux/sched_clock.h>

#include <asm/timex.h>
#include <asm/platform.h>


unsigned long ccount_freq;		
/* ccount Hz */

EXPORT_SYMBOL(ccount_freq);


static cycle_t ccount_read(struct clocksource *cs) { return (cycle_t)get_ccount(); }

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static u64 notrace ccount_sched_clock_read(void) { return get_ccount(); }

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static struct clocksource ccount_clocksource = { .name = "ccount", .rating = 200, .read = ccount_read, .mask = CLOCKSOURCE_MASK(32), .flags = CLOCK_SOURCE_IS_CONTINUOUS, }; static int ccount_timer_set_next_event(unsigned long delta, struct clock_event_device *dev); struct ccount_timer { struct clock_event_device evt; int irq_enabled; char name[24]; }; static DEFINE_PER_CPU(struct ccount_timer, ccount_timer);
static int ccount_timer_set_next_event(unsigned long delta, struct clock_event_device *dev) { unsigned long flags, next; int ret = 0; local_irq_save(flags); next = get_ccount() + delta; set_linux_timer(next); if (next - get_ccount() > delta) ret = -ETIME; local_irq_restore(flags); return ret; }

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/* * There is no way to disable the timer interrupt at the device level, * only at the intenable register itself. Since enable_irq/disable_irq * calls are nested, we need to make sure that these calls are * balanced. */
static int ccount_timer_shutdown(struct clock_event_device *evt) { struct ccount_timer *timer = container_of(evt, struct ccount_timer, evt); if (timer->irq_enabled) { disable_irq(evt->irq); timer->irq_enabled = 0; } return 0; }

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static int ccount_timer_set_oneshot(struct clock_event_device *evt) { struct ccount_timer *timer = container_of(evt, struct ccount_timer, evt); if (!timer->irq_enabled) { enable_irq(evt->irq); timer->irq_enabled = 1; } return 0; }

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static irqreturn_t timer_interrupt(int irq, void *dev_id); static struct irqaction timer_irqaction = { .handler = timer_interrupt, .flags = IRQF_TIMER, .name = "timer", };
void local_timer_setup(unsigned cpu) { struct ccount_timer *timer = &per_cpu(ccount_timer, cpu); struct clock_event_device *clockevent = &timer->evt; timer->irq_enabled = 1; clockevent->name = timer->name; snprintf(timer->name, sizeof(timer->name), "ccount_clockevent_%u", cpu); clockevent->features = CLOCK_EVT_FEAT_ONESHOT; clockevent->rating = 300; clockevent->set_next_event = ccount_timer_set_next_event; clockevent->set_state_shutdown = ccount_timer_shutdown; clockevent->set_state_oneshot = ccount_timer_set_oneshot; clockevent->tick_resume = ccount_timer_set_oneshot; clockevent->cpumask = cpumask_of(cpu); clockevent->irq = irq_create_mapping(NULL, LINUX_TIMER_INT); if (WARN(!clockevent->irq, "error: can't map timer irq")) return; clockevents_config_and_register(clockevent, ccount_freq, 0xf, 0xffffffff); }

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void __init time_init(void) { #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT printk("Calibrating CPU frequency "); platform_calibrate_ccount(); printk("%d.%02d MHz\n", (int)ccount_freq/1000000, (int)(ccount_freq/10000)%100); #else ccount_freq = CONFIG_XTENSA_CPU_CLOCK*1000000UL; #endif clocksource_register_hz(&ccount_clocksource, ccount_freq); local_timer_setup(0); setup_irq(this_cpu_ptr(&ccount_timer)->evt.irq, &timer_irqaction); sched_clock_register(ccount_sched_clock_read, 32, ccount_freq); clocksource_probe(); }

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john stultzjohn stultz44.30%17.14%
stephen boydstephen boyd11.08%17.14%
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marc zyngiermarc zyngier11.08%17.14%
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/* * The timer interrupt is called HZ times per second. */
irqreturn_t timer_interrupt(int irq, void *dev_id) { struct clock_event_device *evt = &this_cpu_ptr(&ccount_timer)->evt; set_linux_timer(get_linux_timer()); evt->event_handler(evt); /* Allow platform to do something useful (Wdog). */ platform_heartbeat(); return IRQ_HANDLED; }

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#ifndef CONFIG_GENERIC_CALIBRATE_DELAY
void calibrate_delay(void) { loops_per_jiffy = ccount_freq / HZ; printk("Calibrating delay loop (skipped)... " "%lu.%02lu BogoMIPS preset\n", loops_per_jiffy/(1000000/HZ), (loops_per_jiffy/(10000/HZ)) % 100); }

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#endif

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viresh kumarviresh kumar497.09%14.76%
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