m68knommu: fix ColdFire timer off by 1

The coldfire timer runs from 0 to TRR included, then 0 again and so on.  It
counts thus actually TRR + 1 steps for 1 tick, not TRR.  Fix that.

Signed-off-by: Philippe De Muyter <phdm@macqel.be>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/arch/m68knommu/platform/5307/timers.c b/arch/m68knommu/platform/5307/timers.c
index 92e58070b01..fb66eadd589 100644
--- a/arch/m68knommu/platform/5307/timers.c
+++ b/arch/m68knommu/platform/5307/timers.c
@@ -62,10 +62,13 @@ void coldfire_tick(void)
 
 /***************************************************************************/
 
+static int ticks_per_intr;
+
 void coldfire_timer_init(irq_handler_t handler)
 {
         __raw_writew(MCFTIMER_TMR_DISABLE, TA(MCFTIMER_TMR));
-        __raw_writetrr(((MCF_BUSCLK / 16) / HZ), TA(MCFTIMER_TRR));
+        ticks_per_intr = (MCF_BUSCLK / 16) / HZ;
+        __raw_writetrr(ticks_per_intr - 1, TA(MCFTIMER_TRR));
         __raw_writew(MCFTIMER_TMR_ENORI | MCFTIMER_TMR_CLK16 |
                 MCFTIMER_TMR_RESTART | MCFTIMER_TMR_ENABLE, TA(MCFTIMER_TMR));
 
@@ -81,11 +84,10 @@ void coldfire_timer_init(irq_handler_t handler)
 
 unsigned long coldfire_timer_offset(void)
 {
-        unsigned long trr, tcn, offset;
+        unsigned long tcn, offset;
 
         tcn = __raw_readw(TA(MCFTIMER_TCN));
-        trr = __raw_readtrr(TA(MCFTIMER_TRR));
-        offset = (tcn * (1000000 / HZ)) / trr;
+        offset = ((tcn + 1) * (1000000 / HZ)) / ticks_per_intr;
 
         /* Check if we just wrapped the counters and maybe missed a tick */
         if ((offset < (1000000 / HZ / 2)) && mcf_timerirqpending(1))