Plain (unsigned) integer division simply truncates the results. The
overall errors are smaller though if we use proper rounding. (Extend
this to the purely cosmetic aspect of time.c's freq_string(), which
before this change I've frequently observed to report e.g. NN.999MHz
HPET clock speeds.)
Signed-off-by: Jan Beulich <jbeul...@suse.com>
---
We could switch at least the first div/rem pair in calibrate_APIC_clock()
to use do_div(), but this would imply switching bus_freq (and then also
result) to unsigned int (as the divisor has to be 32-bit). While I think
there's pretty little risk for bus frequencies to go beyond 4GHz in the
next so many years, I still wasn't certain enough this would be a welcome
change.
--- a/xen/arch/x86/apic.c
+++ b/xen/arch/x86/apic.c
@@ -1261,7 +1261,9 @@ static int __init calibrate_APIC_clock(v
/* set up multipliers for accurate timer code */
bus_freq = result*HZ;
bus_cycle = (u32) (1000000000000LL/bus_freq); /* in pico seconds */
+ bus_cycle += (1000000000000UL % bus_freq) * 2 > bus_freq;
bus_scale = (1000*262144)/bus_cycle;
+ bus_scale += ((1000 * 262144) % bus_cycle) * 2 > bus_cycle;
apic_printk(APIC_VERBOSE, "..... bus_scale = %#x\n", bus_scale);
/* reset APIC to zero timeout value */
--- a/xen/arch/x86/hpet.c
+++ b/xen/arch/x86/hpet.c
@@ -799,9 +799,9 @@ u64 __init hpet_setup(void)
hpet_resume(hpet_boot_cfg);
hpet_rate = 1000000000000000ULL; /* 10^15 */
- (void)do_div(hpet_rate, hpet_period);
+ last = do_div(hpet_rate, hpet_period);
- return hpet_rate;
+ return hpet_rate + (last * 2 > hpet_period);
}
void hpet_resume(u32 *boot_cfg)
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -275,7 +275,10 @@ static char *freq_string(u64 freq)
{
static char s[20];
unsigned int x, y;
- y = (unsigned int)do_div(freq, 1000000) / 1000;
+
+ if ( do_div(freq, 1000) > 500 )
+ ++freq;
+ y = (unsigned int)do_div(freq, 1000);
x = (unsigned int)freq;
snprintf(s, sizeof(s), "%u.%03uMHz", x, y);
return s;
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