[XTENSA] Fix timer instabilities.

The timer code could have missed a tick.

Signed-off-by: Chris Zankel <chris@zankel.net>

diff --git a/arch/xtensa/kernel/time.c b/arch/xtensa/kernel/time.c
index 22949be..60d29fe 100644 (file)
--- a/arch/xtensa/kernel/time.c
+++ b/arch/xtensa/kernel/time.c
@@ -32,12 +32,20 @@ EXPORT_SYMBOL(rtc_lock);
 
 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
 unsigned long ccount_per_jiffy;                /* per 1/HZ */
-unsigned long ccount_nsec;             /* nsec per ccount increment */
+unsigned long nsec_per_ccount;         /* nsec per ccount increment */
 #endif
 
-unsigned int last_ccount_stamp;
 static long last_rtc_update = 0;
 
+/*
+ * Scheduler clock - returns current tim in nanosec units.
+ */
+
+unsigned long long sched_clock(void)
+{
+       return (unsigned long long)jiffies * (1000000000 / HZ);
+}
+
 static irqreturn_t timer_interrupt(int irq, void *dev_id);
 static struct irqaction timer_irqaction = {
        .handler =      timer_interrupt,
@@ -69,7 +77,6 @@ void __init time_init(void)
 
        xtime.tv_nsec = 0;
        last_rtc_update = xtime.tv_sec = sec_n;
-       last_ccount_stamp = get_ccount();
 
        set_normalized_timespec(&wall_to_monotonic,
                -xtime.tv_sec, -xtime.tv_nsec);
@@ -85,7 +92,7 @@ int do_settimeofday(struct timespec *tv)
 {
        time_t wtm_sec, sec = tv->tv_sec;
        long wtm_nsec, nsec = tv->tv_nsec;
-       unsigned long ccount;
+       unsigned long delta;
 
        if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
                return -EINVAL;
@@ -97,8 +104,10 @@ int do_settimeofday(struct timespec *tv)
         * wall time.  Discover what correction gettimeofday() would have
         * made, and then undo it!
         */
-       ccount = get_ccount();
-       nsec -= (ccount - last_ccount_stamp) * CCOUNT_NSEC;
+
+       delta = CCOUNT_PER_JIFFY;
+       delta += get_ccount() - get_linux_timer();
+       nsec -= delta * NSEC_PER_CCOUNT;
 
        wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
        wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
@@ -117,17 +126,21 @@ EXPORT_SYMBOL(do_settimeofday);
 void do_gettimeofday(struct timeval *tv)
 {
        unsigned long flags;
-       unsigned long sec, usec, delta, seq;
+       unsigned long volatile sec, usec, delta, seq;
 
        do {
                seq = read_seqbegin_irqsave(&xtime_lock, flags);
 
-               delta = get_ccount() - last_ccount_stamp;
                sec = xtime.tv_sec;
                usec = (xtime.tv_nsec / NSEC_PER_USEC);
+
+               delta = get_linux_timer() - get_ccount();
+
        } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
 
-       usec += (delta * CCOUNT_NSEC) / NSEC_PER_USEC;
+       usec += (((unsigned long) CCOUNT_PER_JIFFY - delta)
+                * (unsigned long) NSEC_PER_CCOUNT) / NSEC_PER_USEC;
+
        for (; usec >= 1000000; sec++, usec -= 1000000)
                ;
 
@@ -158,9 +171,12 @@ again:
 
                write_seqlock(&xtime_lock);
 
-               last_ccount_stamp = next;
+               do_timer(1); /* Linux handler in kernel/timer.c */
+
+               /* Note that writing CCOMPARE clears the interrupt. */
+
                next += CCOUNT_PER_JIFFY;
-               do_timer (1); /* Linux handler in kernel/timer.c */
+               set_linux_timer(next);
 
                if (ntp_synced() &&
                    xtime.tv_sec - last_rtc_update >= 659 &&
@@ -175,19 +191,15 @@ again:
                write_sequnlock(&xtime_lock);
        }
 
-       /* NOTE: writing CCOMPAREn clears the interrupt.  */
+       /* Allow platform to do something useful (Wdog). */
 
-       set_linux_timer (next);
+       platform_heartbeat();
 
        /* Make sure we didn't miss any tick... */
 
        if ((signed long)(get_ccount() - next) > 0)
                goto again;
 
-       /* Allow platform to do something useful (Wdog). */
-
-       platform_heartbeat();
-
        return IRQ_HANDLED;
 }
 

diff --git a/include/asm-xtensa/timex.h b/include/asm-xtensa/timex.h
index 28c7985..a5fca59 100644 (file)
--- a/include/asm-xtensa/timex.h
+++ b/include/asm-xtensa/timex.h
@@ -41,10 +41,10 @@
 extern unsigned long ccount_per_jiffy;
 extern unsigned long ccount_nsec;
 #define CCOUNT_PER_JIFFY ccount_per_jiffy
-#define CCOUNT_NSEC ccount_nsec
+#define NSEC_PER_CCOUNT  ccount_nsec
 #else
 #define CCOUNT_PER_JIFFY (CONFIG_XTENSA_CPU_CLOCK*(1000000UL/HZ))
-#define CCOUNT_NSEC (1000000000UL / CONFIG_XTENSA_CPU_CLOCK)
+#define NSEC_PER_CCOUNT (1000UL / CONFIG_XTENSA_CPU_CLOCK)
 #endif