arch/arm/mach-ks8695/time.c

   1 /*
   2  * arch/arm/mach-ks8695/time.c
   3  *
   4  * Copyright (C) 2006 Ben Dooks <ben@simtec.co.uk>
   5  * Copyright (C) 2006 Simtec Electronics
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 #include <linux/init.h>
  23 #include <linux/interrupt.h>
  24 #include <linux/irq.h>
  25 #include <linux/kernel.h>
  26 #include <linux/sched.h>
  27 #include <linux/io.h>
  28
  29 #include <asm/mach/time.h>
  30
  31 #include <mach/regs-timer.h>
  32 #include <mach/regs-irq.h>
  33
  34 #include "generic.h"
  35
  36 /*
  37  * Returns number of ms since last clock interrupt.  Note that interrupts
  38  * will have been disabled by do_gettimeoffset()
  39  */
  40 static unsigned long ks8695_gettimeoffset (void)
  41 {
  42         unsigned long elapsed, tick2, intpending;
  43
  44         /*
  45          * Get the current number of ticks.  Note that there is a race
  46          * condition between us reading the timer and checking for an
  47          * interrupt.  We solve this by ensuring that the counter has not
  48          * reloaded between our two reads.
  49          */
  50         elapsed = __raw_readl(KS8695_TMR_VA + KS8695_T1TC) + __raw_readl(KS8695_TMR_VA + KS8695_T1PD);
  51         do {
  52                 tick2 = elapsed;
  53                 intpending = __raw_readl(KS8695_IRQ_VA + KS8695_INTST) & (1 << KS8695_IRQ_TIMER1);
  54                 elapsed = __raw_readl(KS8695_TMR_VA + KS8695_T1TC) + __raw_readl(KS8695_TMR_VA + KS8695_T1PD);
  55         } while (elapsed > tick2);
  56
  57         /* Convert to number of ticks expired (not remaining) */
  58         elapsed = (CLOCK_TICK_RATE / HZ) - elapsed;
  59
  60         /* Is interrupt pending?  If so, then timer has been reloaded already. */
  61         if (intpending)
  62                 elapsed += (CLOCK_TICK_RATE / HZ);
  63
  64         /* Convert ticks to usecs */
  65         return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
  66 }
  67
  68 /*
  69  * IRQ handler for the timer.
  70  */
  71 static irqreturn_t ks8695_timer_interrupt(int irq, void *dev_id)
  72 {
  73         timer_tick();
  74         return IRQ_HANDLED;
  75 }
  76
  77 static struct irqaction ks8695_timer_irq = {
  78         .name           = "ks8695_tick",
  79         .flags          = IRQF_DISABLED | IRQF_TIMER,
  80         .handler        = ks8695_timer_interrupt,
  81 };
  82
  83 static void ks8695_timer_setup(void)
  84 {
  85         unsigned long tmout = CLOCK_TICK_RATE / HZ;
  86         unsigned long tmcon;
  87
  88         /* disable timer1 */
  89         tmcon = __raw_readl(KS8695_TMR_VA + KS8695_TMCON);
  90         __raw_writel(tmcon & ~TMCON_T1EN, KS8695_TMR_VA + KS8695_TMCON);
  91
  92         __raw_writel(tmout / 2, KS8695_TMR_VA + KS8695_T1TC);
  93         __raw_writel(tmout / 2, KS8695_TMR_VA + KS8695_T1PD);
  94
  95         /* re-enable timer1 */
  96         __raw_writel(tmcon | TMCON_T1EN, KS8695_TMR_VA + KS8695_TMCON);
  97 }
  98
  99 static void __init ks8695_timer_init (void)
 100 {
 101         ks8695_timer_setup();
 102
 103         /* Enable timer interrupts */
 104         setup_irq(KS8695_IRQ_TIMER1, &ks8695_timer_irq);
 105 }
 106
 107 struct sys_timer ks8695_timer = {
 108         .init           = ks8695_timer_init,
 109         .offset         = ks8695_gettimeoffset,
 110         .resume         = ks8695_timer_setup,
 111 };