static unsigned long long monotonic_base;
static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED;
+/* Avoid compensating for lost ticks before TSCs are synched */
+static int detect_lost_ticks;
+static int __init start_lost_tick_compensation(void)
+{
+ detect_lost_ticks = 1;
+ return 0;
+}
+late_initcall(start_lost_tick_compensation);
+
/* convert from cycles(64bits) => nanoseconds (64bits)
* basic equation:
* ns = cycles / (freq / ns_per_sec)
* ns = cycles * (ns_per_sec / freq)
- * ns = cycles * (10^9 / (cpu_mhz * 10^6))
- * ns = cycles * (10^3 / cpu_mhz)
+ * ns = cycles * (10^9 / (cpu_khz * 10^3))
+ * ns = cycles * (10^6 / cpu_khz)
*
* Then we use scaling math (suggested by george@mvista.com) to get:
- * ns = cycles * (10^3 * SC / cpu_mhz) / SC
+ * ns = cycles * (10^6 * SC / cpu_khz) / SC
* ns = cycles * cyc2ns_scale / SC
*
* And since SC is a constant power of two, we can convert the div
- * into a shift.
+ * into a shift.
+ *
+ * We can use khz divisor instead of mhz to keep a better percision, since
+ * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
+ * (mathieu.desnoyers@polymtl.ca)
+ *
* -johnstul@us.ibm.com "math is hard, lets go shopping!"
*/
static unsigned long cyc2ns_scale;
#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
-static inline void set_cyc2ns_scale(unsigned long cpu_mhz)
+static inline void set_cyc2ns_scale(unsigned long cpu_khz)
{
- cyc2ns_scale = (1000 << CYC2NS_SCALE_FACTOR)/cpu_mhz;
+ cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
}
static inline unsigned long long cycles_2_ns(unsigned long long cyc)
/* lost tick compensation */
offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
- if (unlikely(((offset - hpet_last) > hpet_tick) && (hpet_last != 0))) {
+ if (unlikely(((offset - hpet_last) > hpet_tick) && (hpet_last != 0))
+ && detect_lost_ticks) {
int lost_ticks = (offset - hpet_last) / hpet_tick;
jiffies_64 += lost_ticks;
}
if (val != CPUFREQ_RESUMECHANGE)
write_seqlock_irq(&xtime_lock);
if (!ref_freq) {
+ if (!freq->old){
+ ref_freq = freq->new;
+ goto end;
+ }
ref_freq = freq->old;
loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy;
#ifndef CONFIG_SMP
if (use_tsc) {
if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_ref, freq->new, ref_freq);
- set_cyc2ns_scale(cpu_khz/1000);
+ set_cyc2ns_scale(cpu_khz);
}
}
#endif
}
+end:
if (val != CPUFREQ_RESUMECHANGE)
write_sequnlock_irq(&xtime_lock);
unsigned int cpu_khz_old = cpu_khz;
if (cpu_has_tsc) {
+ local_irq_disable();
init_cpu_khz();
+ local_irq_enable();
cpu_data[0].loops_per_jiffy =
cpufreq_scale(cpu_data[0].loops_per_jiffy,
cpu_khz_old,
delta += delay_at_last_interrupt;
lost = delta/(1000000/HZ);
delay = delta%(1000000/HZ);
- if (lost >= 2) {
+ if (lost >= 2 && detect_lost_ticks) {
jiffies_64 += lost-1;
/* sanity check to ensure we're not always losing ticks */
printk("Detected %u.%03u MHz processor.\n",
cpu_khz / 1000, cpu_khz % 1000);
}
- set_cyc2ns_scale(cpu_khz/1000);
+ set_cyc2ns_scale(cpu_khz);
return 0;
}
}