text: /*
   * 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/clk.h>
  #include <linux/clk-provider.h>
  #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 u64 ccount_read(struct clocksource *cs)
  {
  	return (u64)get_ccount();
  }
  
  static u64 notrace ccount_sched_clock_read(void)
  {
  	return get_ccount();
  }
  
  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;
  }
  
  /*
   * 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;
  }
  
  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;
  }
  
  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);
  }
  
  #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  #ifdef CONFIG_OF
  static void __init calibrate_ccount(void)
  {
  	struct device_node *cpu;
  	struct clk *clk;
  
  	cpu = of_find_compatible_node(NULL, NULL, "cdns,xtensa-cpu");
  	if (cpu) {
  		clk = of_clk_get(cpu, 0);
  		if (!IS_ERR(clk)) {
  			ccount_freq = clk_get_rate(clk);
  			return;
  		} else {
  			pr_warn("%s: CPU input clock not found\n",
  				__func__);
  		}
  	} else {
  		pr_warn("%s: CPU node not found in the device tree\n",
  			__func__);
  	}
  
  	platform_calibrate_ccount();
  }
  #else
  static inline void calibrate_ccount(void)
  {
  	platform_calibrate_ccount();
  }
  #endif
  #endif
  
  void __init time_init(void)
  {
  	of_clk_init(NULL);
  #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  	pr_info("Calibrating CPU frequency ");
  	calibrate_ccount();
  	pr_cont("%d.%02d MHz\n",
  		(int)ccount_freq / 1000000,
  		(int)(ccount_freq / 10000) % 100);
  #else
  	ccount_freq = CONFIG_XTENSA_CPU_CLOCK*1000000UL;
  #endif
  	WARN(!ccount_freq,
  	     "%s: CPU clock frequency is not set up correctly\n",
  	     __func__);
  	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();
  }
  
  /*
   * 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;
  }
  
  #ifndef CONFIG_GENERIC_CALIBRATE_DELAY
  void calibrate_delay(void)
  {
  	loops_per_jiffy = ccount_freq / HZ;
  	pr_info("Calibrating delay loop (skipped)... %lu.%02lu BogoMIPS preset\n",
  		loops_per_jiffy / (1000000 / HZ),
  		(loops_per_jiffy / (10000 / HZ)) % 100);
  }
  #endif
  