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PowerPC: Switch to more accurate unit to avoid division rounding

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On POWER8 architecture there is a timer with 512Mhz frequency.
It has about 1,95ns period, but it is rounded to 1ns which is not accurate.

Submitted by:          Patryk Duda <pdk@semihalf.com>
Obtained from:         Semihalf
Reviewed by:           wma
Sponsored by:          IBM, QCM Technologies
Differential revision: https://reviews.freebsd.org/D14433
This commit is contained in:
Wojciech Macek 2018-02-20 07:30:57 +00:00
parent 838070d5f4
commit f32ebdc85c
1 changed files with 3 additions and 3 deletions
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6
sys/powerpc/powerpc/clock.c
View File

@ -82,7 +82,7 @@ __FBSDID("$FreeBSD$");
* Initially we assume a processor with a bus frequency of 12.5 MHz.
*/
static int initialized = 0;
static u_long ns_per_tick = 80;
static uint64_t ps_per_tick = 80000;
static u_long ticks_per_sec = 12500000;
static u_long *decr_counts[MAXCPU];
@ -178,7 +178,7 @@ decr_init(void)
if (platform_smp_get_bsp(&cpu) != 0)
platform_smp_first_cpu(&cpu);
ticks_per_sec = platform_timebase_freq(&cpu);
ns_per_tick = 1000000000 / ticks_per_sec;
ps_per_tick = 1000000000000 / ticks_per_sec;
set_cputicker(mftb, ticks_per_sec, 0);
snprintf(buf, sizeof(buf), "cpu%d:decrementer", curcpu);
@ -307,7 +307,7 @@ DELAY(int n)
TSENTER();
tb = mftb();
ttb = tb + howmany(n * 1000, ns_per_tick);
ttb = tb + howmany((uint64_t)n * 1000000, ps_per_tick);
while (tb < ttb)
tb = mftb();
TSEXIT();