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

   1 /* defines for inline arch setup functions */
   2
   3 #include <asm/apic.h>
   4 #include <asm/i8259.h>
   5
   6 /**
   7  * do_timer_interrupt_hook - hook into timer tick
   8  * @regs:       standard registers from interrupt
   9  *
  10  * Description:
  11  *      This hook is called immediately after the timer interrupt is ack'd.
  12  *      It's primary purpose is to allow architectures that don't possess
  13  *      individual per CPU clocks (like the CPU APICs supply) to broadcast the
  14  *      timer interrupt as a means of triggering reschedules etc.
  15  **/
  16
  17 static inline void do_timer_interrupt_hook(void)
  18 {
  19         do_timer(1);
  20 #ifndef CONFIG_SMP
  21         update_process_times(user_mode_vm(get_irq_regs()));
  22 #endif
  23 /*
  24  * In the SMP case we use the local APIC timer interrupt to do the
  25  * profiling, except when we simulate SMP mode on a uniprocessor
  26  * system, in that case we have to call the local interrupt handler.
  27  */
  28 #ifndef CONFIG_X86_LOCAL_APIC
  29         profile_tick(CPU_PROFILING);
  30 #else
  31         if (!using_apic_timer)
  32                 smp_local_timer_interrupt();
  33 #endif
  34 }
  35
  36
  37 /* you can safely undefine this if you don't have the Neptune chipset */
  38
  39 #define BUGGY_NEPTUN_TIMER
  40
  41 /**
  42  * do_timer_overflow - process a detected timer overflow condition
  43  * @count:      hardware timer interrupt count on overflow
  44  *
  45  * Description:
  46  *      This call is invoked when the jiffies count has not incremented but
  47  *      the hardware timer interrupt has.  It means that a timer tick interrupt
  48  *      came along while the previous one was pending, thus a tick was missed
  49  **/
  50 static inline int do_timer_overflow(int count)
  51 {
  52         int i;
  53
  54         spin_lock(&i8259A_lock);
  55         /*
  56          * This is tricky when I/O APICs are used;
  57          * see do_timer_interrupt().
  58          */
  59         i = inb(0x20);
  60         spin_unlock(&i8259A_lock);
  61
  62         /* assumption about timer being IRQ0 */
  63         if (i & 0x01) {
  64                 /*
  65                  * We cannot detect lost timer interrupts ...
  66                  * well, that's why we call them lost, don't we? :)
  67                  * [hmm, on the Pentium and Alpha we can ... sort of]
  68                  */
  69                 count -= LATCH;
  70         } else {
  71 #ifdef BUGGY_NEPTUN_TIMER
  72                 /*
  73                  * for the Neptun bug we know that the 'latch'
  74                  * command doesn't latch the high and low value
  75                  * of the counter atomically. Thus we have to
  76                  * substract 256 from the counter
  77                  * ... funny, isnt it? :)
  78                  */
  79
  80                 count -= 256;
  81 #else
  82                 printk("do_slow_gettimeoffset(): hardware timer problem?\n");
  83 #endif
  84         }
  85         return count;
  86 }