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From: Wojciech Macek <wma@FreeBSD.org>
Date: Tue, 20 Feb 2018 07:30:57 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
svn-src-head@freebsd.org
Subject: svn commit: r329635 - head/sys/powerpc/powerpc
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X-SVN-Commit-Author: wma
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X-List-Received-Date: Tue, 20 Feb 2018 07:30:58 -0000
Author: wma
Date: Tue Feb 20 07:30:57 2018
New Revision: 329635
URL: https://svnweb.freebsd.org/changeset/base/329635
Log:
PowerPC: Switch to more accurate unit to avoid division rounding
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
Modified:
head/sys/powerpc/powerpc/clock.c
Modified: head/sys/powerpc/powerpc/clock.c
==============================================================================
--- head/sys/powerpc/powerpc/clock.c Tue Feb 20 06:38:55 2018 (r329634)
+++ head/sys/powerpc/powerpc/clock.c Tue Feb 20 07:30:57 2018 (r329635)
@@ -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();