[src/trunk]: src/sys/arch/arm/cortex - fix sc_ev_missing_ticks over-counting.

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

details:   https://anonhg.NetBSD.org/src/rev/5b018b14a8d8
branches:  trunk
changeset: 809613:5b018b14a8d8
user:      ryo <ryo%NetBSD.org@localhost>
date:      Fri Jul 24 05:19:13 2015 +0000

description:
- fix sc_ev_missing_ticks over-counting.
- don't use 64bit division, because it has expensive cost on gcc/arm
  whether it is a constant or not.

'delta' is usually taken a value around sc_autoinc depending on timing
of read. therefore 'delta / sc->sc_autoinc' would be count too much.

diffstat:

 sys/arch/arm/cortex/a9tmr.c |  32 +++++++++++++++++---------------
 1 files changed, 17 insertions(+), 15 deletions(-)

diffs (62 lines):

diff -r 5448f2c91801 -r 5b018b14a8d8 sys/arch/arm/cortex/a9tmr.c
--- a/sys/arch/arm/cortex/a9tmr.c       Fri Jul 24 04:33:50 2015 +0000
+++ b/sys/arch/arm/cortex/a9tmr.c       Fri Jul 24 05:19:13 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: a9tmr.c,v 1.12 2015/03/04 23:18:21 jmcneill Exp $      */
+/*     $NetBSD: a9tmr.c,v 1.13 2015/07/24 05:19:13 ryo Exp $   */
 
 /*-
  * Copyright (c) 2012 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: a9tmr.c,v 1.12 2015/03/04 23:18:21 jmcneill Exp $");
+__KERNEL_RCSID(0, "$NetBSD: a9tmr.c,v 1.13 2015/07/24 05:19:13 ryo Exp $");
 
 #include <sys/param.h>
 #include <sys/bus.h>
@@ -329,7 +329,7 @@
        printf("%s(%p): %s: now %#"PRIx64" delta %"PRIu64"\n", 
             __func__, cf, ci->ci_data.cpu_name, now, delta);
 #endif
-       KASSERTMSG(delta > sc->sc_autoinc / 100,
+       KASSERTMSG(delta > sc->sc_autoinc / 64,
            "%s: interrupting too quickly (delta=%"PRIu64")",
            ci->ci_data.cpu_name, delta);
 
@@ -337,20 +337,22 @@
 
        hardclock(cf);
 
+       if (delta > sc->sc_autoinc) {
+               u_int ticks = hz;
+               for (delta -= sc->sc_autoinc;
+                    delta >= sc->sc_autoinc && ticks > 0;
+                    delta -= sc->sc_autoinc, ticks--) {
 #if 0
-       /*
-        * Try to make up up to a seconds amount of missed clock interrupts
-        */
-       u_int ticks = hz;
-       for (delta -= sc->sc_autoinc;
-            ticks > 0 && delta >= sc->sc_autoinc;
-            delta -= sc->sc_autoinc, ticks--) {
-               hardclock(cf);
+                       /*
+                        * Try to make up up to a seconds amount of
+                        * missed clock interrupts
+                        */
+                       hardclock(cf);
+#else
+                       sc->sc_ev_missing_ticks.ev_count++;
+#endif
+               }
        }
-#else
-       if (delta > sc->sc_autoinc)
-               sc->sc_ev_missing_ticks.ev_count += delta / sc->sc_autoinc;
-#endif
 
        return 1;
 }