[src/trunk]: src/sys/arch/sh3/sh3 fix microtime()

[msaitoh <msaitoh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/85eefface972
branches:  trunk
changeset: 511669:85eefface972
user:      msaitoh <msaitoh%NetBSD.org@localhost>
date:      Sun Jun 24 05:00:28 2001 +0000

description:
fix microtime()

diffstat:

 sys/arch/sh3/sh3/clock.c |  33 ++++++++++++++++++++++++++++++++-
 1 files changed, 32 insertions(+), 1 deletions(-)

diffs (57 lines):

diff -r 2e686b4e427e -r 85eefface972 sys/arch/sh3/sh3/clock.c
--- a/sys/arch/sh3/sh3/clock.c  Sun Jun 24 04:57:58 2001 +0000
+++ b/sys/arch/sh3/sh3/clock.c  Sun Jun 24 05:00:28 2001 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: clock.c,v 1.15 2001/04/23 11:20:41 uch Exp $   */
+/*     $NetBSD: clock.c,v 1.16 2001/06/24 05:00:28 msaitoh Exp $       */
 
 /*-
  * Copyright (c) 1993, 1994 Charles Hannum.
@@ -142,9 +142,39 @@
 {
        int s = splclock();
        static struct timeval lasttime;
+       static u_long numerator = 0;
+       static u_long denominator = 0;
 
+       /*
+        * 1/hz resolution ``time'' which is counted up at hardclock().
+        */
        *tvp = time;
 
+       /*
+        * diff = (PCLOCK/16/hz - 1 - SHREG_TCNT1) / (PCLOCK/16/hz - 1)
+        *         * 1/hz * 10^6. [usec]
+        */
+
+       if (denominator == 0) {
+               numerator = 1000000 / hz;
+               denominator = PCLOCK/16/hz - 1;
+       }
+
+       diff = (denominator - SHREG_TCNT1) * numerator / denominator;
+
+       /*
+        * add ``diff'' to ``time''
+        */
+       tvp->tv_usec += diff;
+       while (tvp->tv_usec >= 1000000) {
+               tvp->tv_usec -= 1000000;
+               tvp->tv_sec++;
+       }
+
+       /*
+        * microtime() always gains 1usec at least.
+        */
+
        if (tvp->tv_sec == lasttime.tv_sec &&
            tvp->tv_usec <= lasttime.tv_usec &&
            (tvp->tv_usec = lasttime.tv_usec + 1) >= 1000000) {
@@ -152,6 +182,7 @@
                tvp->tv_usec -= 1000000;
        }
        lasttime = *tvp;
+
        splx(s);
 }