arch/arm/mach-ns9xxx/time.c

   1 /*
   2  * arch/arm/mach-ns9xxx/time.c
   3  *
   4  * Copyright (C) 2006 by Digi International Inc.
   5  * All rights reserved.
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 as published by
   9  * the Free Software Foundation.
  10  */
  11 #include <linux/jiffies.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/irq.h>
  14 #include <asm/arch-ns9xxx/regs-sys.h>
  15 #include <asm/arch-ns9xxx/clock.h>
  16 #include <asm/arch-ns9xxx/irqs.h>
  17 #include <asm/arch/system.h>
  18 #include "generic.h"
  19
  20 #define TIMERCLOCKSELECT 64
  21
  22 static u32 usecs_per_tick;
  23
  24 static irqreturn_t
  25 ns9xxx_timer_interrupt(int irq, void *dev_id)
  26 {
  27         write_seqlock(&xtime_lock);
  28         timer_tick();
  29         write_sequnlock(&xtime_lock);
  30
  31         return IRQ_HANDLED;
  32 }
  33
  34 static unsigned long ns9xxx_timer_gettimeoffset(void)
  35 {
  36         /* return the microseconds which have passed since the last interrupt
  37          * was _serviced_.  That is, if an interrupt is pending or the counter
  38          * reloads, return one period more. */
  39
  40         u32 counter1 = SYS_TR(0);
  41         int pending = SYS_ISR & (1 << IRQ_TIMER0);
  42         u32 counter2 = SYS_TR(0);
  43         u32 elapsed;
  44
  45         if (pending || counter2 > counter1)
  46                 elapsed = 2 * SYS_TRC(0) - counter2;
  47         else
  48                 elapsed = SYS_TRC(0) - counter1;
  49
  50         return (elapsed * usecs_per_tick) >> 16;
  51
  52 }
  53
  54 static struct irqaction ns9xxx_timer_irq = {
  55         .name = "NS9xxx Timer Tick",
  56         .flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
  57         .handler = ns9xxx_timer_interrupt,
  58 };
  59
  60 static void __init ns9xxx_timer_init(void)
  61 {
  62         int tc;
  63
  64         usecs_per_tick =
  65                 SH_DIV(1000000 * TIMERCLOCKSELECT, ns9xxx_cpuclock(), 16);
  66
  67         /* disable timer */
  68         if ((tc = SYS_TC(0)) & SYS_TCx_TEN)
  69                 SYS_TC(0) = tc & ~SYS_TCx_TEN;
  70
  71         SYS_TRC(0) = SH_DIV(ns9xxx_cpuclock(), (TIMERCLOCKSELECT * HZ), 0);
  72
  73         REGSET(tc, SYS_TCx, TEN, EN);
  74         REGSET(tc, SYS_TCx, TLCS, DIV64); /* This must match TIMERCLOCKSELECT */
  75         REGSET(tc, SYS_TCx, INTS, EN);
  76         REGSET(tc, SYS_TCx, UDS, DOWN);
  77         REGSET(tc, SYS_TCx, TDBG, STOP);
  78         REGSET(tc, SYS_TCx, TSZ, 32);
  79         REGSET(tc, SYS_TCx, REN, EN);
  80         SYS_TC(0) = tc;
  81
  82         setup_irq(IRQ_TIMER0, &ns9xxx_timer_irq);
  83 }
  84
  85 struct sys_timer ns9xxx_timer = {
  86         .init = ns9xxx_timer_init,
  87         .offset = ns9xxx_timer_gettimeoffset,
  88 };