[XTENSA] Fix timer instabilities.

The timer code could have missed a tick.

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

1 files changed, 29 insertions, 17 deletions

diff --git a/arch/xtensa/kernel/time.c b/arch/xtensa/kernel/time.c
index 22949be4a5d8..60d29fe0b1bd 100644
--- 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;
 }