Module Name: src
Committed By: snj
Date: Tue Mar 13 16:48:05 UTC 2018
Modified Files:
src/sys/arch/sparc/sparc [netbsd-6]: timer.c timer_sun4m.c timerreg.h
Log Message:
Pull up following revision(s) (requested by mrg in ticket #1519):
sys/arch/sparc/sparc/timer_sun4m.c: 1.33 1.34 1.31
sys/arch/sparc/sparc/timer.c: 1.33
sys/arch/sparc/sparc/timer.c: 1.33 1.34
sys/arch/sparc/sparc/timerreg.h: 1.33 1.34 1.31 1.10
fix time goes backwards problems on sparc.
there are a few things here:
- there's a race between reading the limit register (which clears
the interrupt and the limit bit) and increasing the latest offset.
this can happen easily if an interrupt comes between the read and
the call to tickle_tc() that increases the offset (i obverved this
actually happening.)
- in early boot, sometimes the counter can cycle twice before the
tickle happens.
to handle these issues, add two workarounds:
- if the limit bit isn't set, but the counter value is less than
the previous value, and the offset hasn't changed, use the same
fixup as if the limit bit was set. this handles the first case
above.
- add a hard-workaround for never allowing returning a smaller
value (except during 32 bit overflow): if the result is less than
the last result, add fixups until it does (or until it would
overflow.)
the first workaround fixes general run-time issues, and the second
fixes issues only seen during boot.
also expand some comments in timer_sun4m.c and re-enable the sun4m
sub-microsecond tmr_ustolim4m() support (but it's always called with
at least 'tick' microseconds, so the end result is the same.)
fix hang at 4B microseconds (1h12 or so), and simplify part of the previous
To generate a diff of this commit:
cvs rdiff -u -r1.29 -r1.29.8.1 src/sys/arch/sparc/sparc/timer.c
cvs rdiff -u -r1.28 -r1.28.8.1 src/sys/arch/sparc/sparc/timer_sun4m.c
cvs rdiff -u -r1.9 -r1.9.118.1 src/sys/arch/sparc/sparc/timerreg.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/sparc/sparc/timer.c
diff -u src/sys/arch/sparc/sparc/timer.c:1.29 src/sys/arch/sparc/sparc/timer.c:1.29.8.1
--- src/sys/arch/sparc/sparc/timer.c:1.29 Sun Jul 17 23:18:23 2011
+++ src/sys/arch/sparc/sparc/timer.c Tue Mar 13 16:48:05 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: timer.c,v 1.29 2011/07/17 23:18:23 mrg Exp $ */
+/* $NetBSD: timer.c,v 1.29.8.1 2018/03/13 16:48:05 snj Exp $ */
/*
* Copyright (c) 1992, 1993
@@ -60,7 +60,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: timer.c,v 1.29 2011/07/17 23:18:23 mrg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: timer.c,v 1.29.8.1 2018/03/13 16:48:05 snj Exp $");
#include <sys/param.h>
#include <sys/kernel.h>
@@ -83,56 +83,93 @@ static u_int timer_get_timecount(struct
* timecounter local state
*/
static struct counter {
- volatile u_int *cntreg; /* counter register */
+ __cpu_simple_lock_t lock; /* protects access to offset, reg, last* */
+ volatile u_int *cntreg; /* counter register to read */
u_int limit; /* limit we count up to */
u_int offset; /* accumulated offet due to wraps */
u_int shift; /* scaling for valid bits */
u_int mask; /* valid bit mask */
-} cntr;
+ u_int lastcnt; /* the last* values are used to notice */
+ u_int lastres; /* and fix up cases where it would appear */
+ u_int lastoffset; /* time went backwards. */
+} cntr __aligned(CACHE_LINE_SIZE);
/*
* define timecounter
*/
static struct timecounter counter_timecounter = {
- timer_get_timecount, /* get_timecount */
- 0, /* no poll_pps */
- ~0u, /* counter_mask */
- 0, /* frequency - set at initialisation */
- "timer-counter", /* name */
- 100, /* quality */
- &cntr /* private reference */
+ .tc_get_timecount = timer_get_timecount,
+ .tc_poll_pps = NULL,
+ .tc_counter_mask = ~0u,
+ .tc_frequency = 0,
+ .tc_name = "timer-counter",
+ .tc_quality = 100,
+ .tc_priv = &cntr,
};
/*
* timer_get_timecount provide current counter value
*/
+__attribute__((__optimize__("Os")))
static u_int
timer_get_timecount(struct timecounter *tc)
{
- struct counter *ctr = (struct counter *)tc->tc_priv;
-
- u_int c, res, r;
+ u_int cnt, res, fixup, offset;
int s;
-
+ /*
+ * We use splhigh/__cpu_simple_lock here as we don't want
+ * any mutex or lockdebug overhead. The lock protects a
+ * bunch of the members of cntr that are written here to
+ * deal with the various minor races to be observed and
+ * worked around.
+ */
s = splhigh();
- res = c = *ctr->cntreg;
+ __cpu_simple_lock(&cntr.lock);
+ res = cnt = *cntr.cntreg;
res &= ~TMR_LIMIT;
+ offset = cntr.offset;
- if (c != res) {
- r = ctr->limit;
+ /*
+ * There are 3 cases here:
+ * - limit reached, interrupt not yet processed.
+ * - count reset but offset the same, race between handling
+ * the interrupt and tickle_tc() updating the offset.
+ * - normal case.
+ *
+ * For the first two cases, add the limit so that we avoid
+ * time going backwards.
+ */
+ if (cnt != res) {
+ fixup = cntr.limit;
+ } else if (res < cntr.lastcnt && offset == cntr.lastoffset) {
+ fixup = cntr.limit;
} else {
- r = 0;
+ fixup = 0;
}
+
+ cntr.lastcnt = res;
+ cntr.lastoffset = offset;
- res >>= ctr->shift;
- res &= ctr->mask;
+ res >>= cntr.shift;
+ res &= cntr.mask;
- res += r + ctr->offset;
+ res += fixup + offset;
+ /*
+ * This handles early-boot cases where the counter resets twice
+ * before the offset is updated, and we have a stupid check to
+ * ensure overflow hasn't happened.
+ */
+ if (res < cntr.lastres && res > (TMR_MASK+1) << 3)
+ res = cntr.lastres + 1;
+
+ cntr.lastres = res;
+
+ __cpu_simple_unlock(&cntr.lock);
splx(s);
return res;
@@ -141,7 +178,15 @@ timer_get_timecount(struct timecounter *
void
tickle_tc(void)
{
+
if (timecounter->tc_get_timecount == timer_get_timecount) {
+ /*
+ * This could be protected by cntr.lock/splhigh but the update
+ * happens at IPL10 already and as a 32 bit value it should
+ * never be seen as a partial update, so skip it here. This
+ * also probably slows down the actual offset update, making
+ * one of the cases above more likely to need the workaround.
+ */
cntr.offset += cntr.limit;
}
}
@@ -189,6 +234,8 @@ timerattach(volatile int *cntreg, volati
if ((1 << t0) & prec)
break;
+ __cpu_simple_lock_init(&cntr.lock);
+
cntr.shift = t0;
cntr.mask = (1 << (31-t0))-1;
counter_timecounter.tc_frequency = 1000000 * (TMR_SHIFT - t0 + 1);
@@ -219,6 +266,7 @@ timerattach(volatile int *cntreg, volati
cntr.limit = tmr_ustolim4m(tick);
}
#endif
+
/* link interrupt handlers */
intr_establish(10, 0, &level10, NULL, true);
intr_establish(14, 0, &level14, NULL, true);
@@ -231,6 +279,9 @@ timerattach(volatile int *cntreg, volati
cntr.cntreg = cntreg;
cntr.limit >>= cntr.shift;
+ /* start at non-zero, so that cntr.oldoffset is less */
+ cntr.offset = cntr.limit;
+
tc_init(&counter_timecounter);
}
Index: src/sys/arch/sparc/sparc/timer_sun4m.c
diff -u src/sys/arch/sparc/sparc/timer_sun4m.c:1.28 src/sys/arch/sparc/sparc/timer_sun4m.c:1.28.8.1
--- src/sys/arch/sparc/sparc/timer_sun4m.c:1.28 Thu Sep 1 08:43:24 2011
+++ src/sys/arch/sparc/sparc/timer_sun4m.c Tue Mar 13 16:48:05 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: timer_sun4m.c,v 1.28 2011/09/01 08:43:24 martin Exp $ */
+/* $NetBSD: timer_sun4m.c,v 1.28.8.1 2018/03/13 16:48:05 snj Exp $ */
/*
* Copyright (c) 1992, 1993
@@ -58,7 +58,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: timer_sun4m.c,v 1.28 2011/09/01 08:43:24 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: timer_sun4m.c,v 1.28.8.1 2018/03/13 16:48:05 snj Exp $");
#include <sys/param.h>
#include <sys/kernel.h>
@@ -74,7 +74,7 @@ __KERNEL_RCSID(0, "$NetBSD: timer_sun4m.
#include <sparc/sparc/timerreg.h>
#include <sparc/sparc/timervar.h>
-struct timer_4m *timerreg4m;
+static struct timer_4m *timerreg4m;
#define counterreg4m cpuinfo.counterreg_4m
/*
@@ -142,9 +142,13 @@ clockintr_4m(void *cap)
*/
if (cold)
return 0;
+
kpreempt_disable();
- /* read the limit register to clear the interrupt */
+
+ /* Read the limit register to clear the interrupt. */
*((volatile int *)&timerreg4m->t_limit);
+
+ /* Update the timecounter offset. */
tickle_tc();
hardclock((struct clockframe *)cap);
kpreempt_enable();
Index: src/sys/arch/sparc/sparc/timerreg.h
diff -u src/sys/arch/sparc/sparc/timerreg.h:1.9 src/sys/arch/sparc/sparc/timerreg.h:1.9.118.1
--- src/sys/arch/sparc/sparc/timerreg.h:1.9 Wed Nov 16 03:00:23 2005
+++ src/sys/arch/sparc/sparc/timerreg.h Tue Mar 13 16:48:05 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: timerreg.h,v 1.9 2005/11/16 03:00:23 uwe Exp $ */
+/* $NetBSD: timerreg.h,v 1.9.118.1 2018/03/13 16:48:05 snj Exp $ */
/*
* Copyright (c) 1992, 1993
@@ -120,9 +120,12 @@ struct counter_4m { /* counter that int
*/
#define tmr_ustolim(n) (((n) + 1) << TMR_SHIFT)
-/*efine TMR_SHIFT4M 9 -* shift to obtain microseconds */
-/*efine tmr_ustolim4m(n) (((2*(n)) + 1) << TMR_SHIFT4M)*/
+#define TMR_SHIFT4M 9 /* shift to obtain microseconds */
+#if 1
+#define tmr_ustolim4m(n) (((2*(n)) + 1) << TMR_SHIFT4M)
+#else
#define tmr_ustolim4m(n) ((n) << TMR_SHIFT)
+#endif
/* The number of microseconds represented by a counter register value */
#define tmr_cnttous(c) ((((c) >> TMR_SHIFT) & TMR_MASK) - 1)
