arch/arm/mach-iop3xx/iop331-time.c

   1 /*
   2  * arch/arm/mach-iop3xx/iop331-time.c
   3  *
   4  * Timer code for IOP331 based systems
   5  *
   6  * Author: Dave Jiang <dave.jiang@intel.com>
   7  *
   8  * Copyright 2003 Intel Corp.
   9  *
  10  *  This program is free software; you can redistribute  it and/or modify it
  11  *  under  the terms of  the GNU General  Public License as published by the
  12  *  Free Software Foundation;  either version 2 of the  License, or (at your
  13  *  option) any later version.
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/time.h>
  19 #include <linux/init.h>
  20 #include <linux/timex.h>
  21
  22 #include <asm/hardware.h>
  23 #include <asm/io.h>
  24 #include <asm/irq.h>
  25 #include <asm/uaccess.h>
  26 #include <asm/mach-types.h>
  27 #include <asm/mach/irq.h>
  28 #include <asm/mach/time.h>
  29
  30 static inline unsigned long get_elapsed(void)
  31 {
  32         return LATCH - *IOP331_TU_TCR0;
  33 }
  34
  35 static unsigned long iop331_gettimeoffset(void)
  36 {
  37         unsigned long elapsed, usec;
  38         u32 tisr1, tisr2;
  39
  40         /*
  41          * If an interrupt was pending before we read the timer,
  42          * we've already wrapped.  Factor this into the time.
  43          * If an interrupt was pending after we read the timer,
  44          * it may have wrapped between checking the interrupt
  45          * status and reading the timer.  Re-read the timer to
  46          * be sure its value is after the wrap.
  47          */
  48
  49         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr1));
  50         elapsed = get_elapsed();
  51         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr2));
  52
  53         if(tisr1 & 1)
  54                 elapsed += LATCH;
  55         else if (tisr2 & 1)
  56                 elapsed = LATCH + get_elapsed();
  57
  58         /*
  59          * Now convert them to usec.
  60          */
  61         usec = (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
  62
  63         return usec;
  64 }
  65
  66 static irqreturn_t
  67 iop331_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  68 {
  69         u32 tisr;
  70
  71         write_seqlock(&xtime_lock);
  72
  73         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr));
  74         tisr |= 1;
  75         asm volatile("mcr p6, 0, %0, c6, c1, 0" : : "r" (tisr));
  76
  77         timer_tick(regs);
  78
  79         write_sequnlock(&xtime_lock);
  80         return IRQ_HANDLED;
  81 }
  82
  83 static struct irqaction iop331_timer_irq = {
  84         .name           = "IOP331 Timer Tick",
  85         .handler        = iop331_timer_interrupt,
  86         .flags          = SA_INTERRUPT
  87 };
  88
  89 static void __init iop331_timer_init(void)
  90 {
  91         u32 timer_ctl;
  92
  93         setup_irq(IRQ_IOP331_TIMER0, &iop331_timer_irq);
  94
  95         timer_ctl = IOP331_TMR_EN | IOP331_TMR_PRIVILEGED | IOP331_TMR_RELOAD |
  96                         IOP331_TMR_RATIO_1_1;
  97
  98         asm volatile("mcr p6, 0, %0, c4, c1, 0" : : "r" (LATCH));
  99
 100         asm volatile("mcr p6, 0, %0, c0, c1, 0" : : "r" (timer_ctl));
 101
 102 }
 103
 104 struct sys_timer iop331_timer = {
 105         .init           = iop331_timer_init,
 106         .offset         = iop331_gettimeoffset,
 107 };