time.c

一个2.4.21版本的嵌入式linux内核

/*
 * Copyright (C) 2000, 2001 Broadcom Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

/*
 * These are routines to set up and handle interrupts from the
 * sb1250 general purpose timer 0.  We're using the timer as a
 * system clock, so we set it up to run at 100 Hz.  On every
 * interrupt, we update our idea of what the time of day is,
 * then call do_timer() in the architecture-independent kernel
 * code to do general bookkeeping (e.g. update jiffies, run
 * bottom halves, etc.)
 */
#include <linux/config.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/kernel_stat.h>

#include <asm/irq.h>
#include <asm/ptrace.h>
#include <asm/addrspace.h>
#include <asm/time.h>

#include <asm/sibyte/sb1250.h>
#include <asm/sibyte/sb1250_regs.h>
#include <asm/sibyte/sb1250_int.h>
#include <asm/sibyte/sb1250_scd.h>
#include <asm/sibyte/64bit.h>


#define IMR_IP2_VAL	K_INT_MAP_I0
#define IMR_IP3_VAL	K_INT_MAP_I1
#define IMR_IP4_VAL	K_INT_MAP_I2

extern int sb1250_steal_irq(int irq);

void sb1250_time_init(void)
{
	int cpu = smp_processor_id();

	/* Only have 4 general purpose timers */
	if (cpu > 3) {
		BUG();
	}

	if (!cpu) {
		/* Use our own gettimeoffset() routine */
		do_gettimeoffset = sb1250_gettimeoffset;
	}

	sb1250_mask_irq(cpu, K_INT_TIMER_0 + cpu);

	/* Map the timer interrupt to ip[4] of this cpu */
	out64(IMR_IP4_VAL, KSEG1 + A_IMR_REGISTER(cpu, R_IMR_INTERRUPT_MAP_BASE)
	      + ((K_INT_TIMER_0 + cpu)<<3));

	/* the general purpose timer ticks at 1 Mhz independent if the rest of the system */
	/* Disable the timer and set up the count */
	out64(0, KSEG1 + A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_CFG));
	out64(
#ifndef CONFIG_SIMULATION
		1000000/HZ
#else
		50000/HZ
#endif
		, KSEG1 + A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_INIT));

	/* Set the timer running */
	out64(M_SCD_TIMER_ENABLE|M_SCD_TIMER_MODE_CONTINUOUS,
	      KSEG1 + A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_CFG));

	sb1250_unmask_irq(cpu, K_INT_TIMER_0 + cpu);
	sb1250_steal_irq(K_INT_TIMER_0 + cpu);
	/*
	 * This interrupt is "special" in that it doesn't use the request_irq
	 * way to hook the irq line.  The timer interrupt is initialized early
	 * enough to make this a major pain, and it's also firing enough to
	 * warrant a bit of special case code.  sb1250_timer_interrupt is
	 * called directly from irq_handler.S when IP[4] is set during an
	 * interrupt
	 */
}

void sb1250_timer_interrupt(struct pt_regs *regs)
{
	int cpu = smp_processor_id();

	kstat.irqs[cpu][K_INT_TIMER_0+cpu]++;
	/* Reset the timer */
	out64(M_SCD_TIMER_ENABLE|M_SCD_TIMER_MODE_CONTINUOUS,
	      KSEG1 + A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_CFG));

	/*
	 * CPU 0 handles the global timer interrupt job
	 */
	if (cpu == 0) {
		ll_timer_interrupt(0, regs);
	}

	/*
	 * every CPU should do profiling and process accouting
	 */
	ll_local_timer_interrupt(0, regs);
}

/*
 * We use our own do_gettimeoffset() instead of the generic one,
 * because the generic one does not work for SMP case.
 * In addition, since we use general timer 0 for system time,
 * we can get accurate intra-jiffy offset without calibration.
 */
unsigned long sb1250_gettimeoffset(void)
{
	unsigned long count =
		in64(KSEG1 + A_SCD_TIMER_REGISTER(0, R_SCD_TIMER_CNT));

	return 1000000/HZ - count;
 }