include/asm-i386/mach-default/do_timer.h

   1 /* defines for inline arch setup functions */
   2
   3 #include <asm/apic.h>
   4
   5 /**
   6  * do_timer_interrupt_hook - hook into timer tick
   7  * @regs:       standard registers from interrupt
   8  *
   9  * Description:
  10  *      This hook is called immediately after the timer interrupt is ack'd.
  11  *      It's primary purpose is to allow architectures that don't possess
  12  *      individual per CPU clocks (like the CPU APICs supply) to broadcast the
  13  *      timer interrupt as a means of triggering reschedules etc.
  14  **/
  15
  16 static inline void do_timer_interrupt_hook(struct pt_regs *regs)
  17 {
  18         do_timer(regs);
  19 #ifndef CONFIG_SMP
  20         update_process_times(user_mode(regs));
  21 #endif
  22 /*
  23  * In the SMP case we use the local APIC timer interrupt to do the
  24  * profiling, except when we simulate SMP mode on a uniprocessor
  25  * system, in that case we have to call the local interrupt handler.
  26  */
  27 #ifndef CONFIG_X86_LOCAL_APIC
  28         profile_tick(CPU_PROFILING, regs);
  29 #else
  30         if (!using_apic_timer)
  31                 smp_local_timer_interrupt(regs);
  32 #endif
  33 }
  34
  35
  36 /* you can safely undefine this if you don't have the Neptune chipset */
  37
  38 #define BUGGY_NEPTUN_TIMER
  39
  40 /**
  41  * do_timer_overflow - process a detected timer overflow condition
  42  * @count:      hardware timer interrupt count on overflow
  43  *
  44  * Description:
  45  *      This call is invoked when the jiffies count has not incremented but
  46  *      the hardware timer interrupt has.  It means that a timer tick interrupt
  47  *      came along while the previous one was pending, thus a tick was missed
  48  **/
  49 static inline int do_timer_overflow(int count)
  50 {
  51         int i;
  52
  53         spin_lock(&i8259A_lock);
  54         /*
  55          * This is tricky when I/O APICs are used;
  56          * see do_timer_interrupt().
  57          */
  58         i = inb(0x20);
  59         spin_unlock(&i8259A_lock);
  60
  61         /* assumption about timer being IRQ0 */
  62         if (i & 0x01) {
  63                 /*
  64                  * We cannot detect lost timer interrupts ...
  65                  * well, that's why we call them lost, don't we? :)
  66                  * [hmm, on the Pentium and Alpha we can ... sort of]
  67                  */
  68                 count -= LATCH;
  69         } else {
  70 #ifdef BUGGY_NEPTUN_TIMER
  71                 /*
  72                  * for the Neptun bug we know that the 'latch'
  73                  * command doesn't latch the high and low value
  74                  * of the counter atomically. Thus we have to
  75                  * substract 256 from the counter
  76                  * ... funny, isnt it? :)
  77                  */
  78
  79                 count -= 256;
  80 #else
  81                 printk("do_slow_gettimeoffset(): hardware timer problem?\n");
  82 #endif
  83         }
  84         return count;
  85 }