arch/x86/include/asm/timer.h

   1 #ifndef _ASM_X86_TIMER_H
   2 #define _ASM_X86_TIMER_H
   3 #include <linux/init.h>
   4 #include <linux/pm.h>
   5 #include <linux/percpu.h>
   6 #include <linux/interrupt.h>
   7
   8 #define TICK_SIZE (tick_nsec / 1000)
   9
  10 unsigned long long native_sched_clock(void);
  11 unsigned long native_calibrate_tsc(void);
  12
  13 #ifdef CONFIG_X86_32
  14 extern int timer_ack;
  15 extern irqreturn_t timer_interrupt(int irq, void *dev_id);
  16 #endif /* CONFIG_X86_32 */
  17 extern int recalibrate_cpu_khz(void);
  18
  19 extern int no_timer_check;
  20
  21 #ifndef CONFIG_PARAVIRT
  22 #define calibrate_tsc() native_calibrate_tsc()
  23 #endif
  24
  25 /* Accelerators for sched_clock()
  26  * convert from cycles(64bits) => nanoseconds (64bits)
  27  *  basic equation:
  28  *              ns = cycles / (freq / ns_per_sec)
  29  *              ns = cycles * (ns_per_sec / freq)
  30  *              ns = cycles * (10^9 / (cpu_khz * 10^3))
  31  *              ns = cycles * (10^6 / cpu_khz)
  32  *
  33  *      Then we use scaling math (suggested by george@mvista.com) to get:
  34  *              ns = cycles * (10^6 * SC / cpu_khz) / SC
  35  *              ns = cycles * cyc2ns_scale / SC
  36  *
  37  *      And since SC is a constant power of two, we can convert the div
  38  *  into a shift.
  39  *
  40  *  We can use khz divisor instead of mhz to keep a better precision, since
  41  *  cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
  42  *  (mathieu.desnoyers@polymtl.ca)
  43  *
  44  *                      -johnstul@us.ibm.com "math is hard, lets go shopping!"
  45  */
  46
  47 DECLARE_PER_CPU(unsigned long, cyc2ns);
  48 DECLARE_PER_CPU(unsigned long long, cyc2ns_offset);
  49
  50 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
  51
  52 static inline unsigned long long __cycles_2_ns(unsigned long long cyc)
  53 {
  54         int cpu = smp_processor_id();
  55         unsigned long long ns = per_cpu(cyc2ns_offset, cpu);
  56         ns += cyc * per_cpu(cyc2ns, cpu) >> CYC2NS_SCALE_FACTOR;
  57         return ns;
  58 }
  59
  60 static inline unsigned long long cycles_2_ns(unsigned long long cyc)
  61 {
  62         unsigned long long ns;
  63         unsigned long flags;
  64
  65         local_irq_save(flags);
  66         ns = __cycles_2_ns(cyc);
  67         local_irq_restore(flags);
  68
  69         return ns;
  70 }
  71
  72 #endif /* _ASM_X86_TIMER_H */