m68knommu: init coldfire timer TRR with n - 1, not n

The coldfire timer must be initialised to n - 1 if we want it to count n
cycles between each tick interrupt.  This was already fixed, but has been
lost with the conversion to GENERIC_TIMER.

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

diff --git a/arch/m68knommu/platform/coldfire/timers.c b/arch/m68knommu/platform/coldfire/timers.c
index ba5a9f32ebd4825ae730cb5f9fd6314c51760707..454f25493491725140bd15f6e74ca61375077d2b 100644 (file)
--- a/arch/m68knommu/platform/coldfire/timers.c
+++ b/arch/m68knommu/platform/coldfire/timers.c
@@ -111,7 +111,13 @@ void hw_timer_init(void)
 
        __raw_writew(MCFTIMER_TMR_DISABLE, TA(MCFTIMER_TMR));
        mcftmr_cycles_per_jiffy = FREQ / HZ;
-       __raw_writetrr(mcftmr_cycles_per_jiffy, TA(MCFTIMER_TRR));
+       /*
+        *      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.  So if you want n cycles,
+        *      initialize TRR with n - 1.
+        */
+       __raw_writetrr(mcftmr_cycles_per_jiffy - 1, TA(MCFTIMER_TRR));
        __raw_writew(MCFTIMER_TMR_ENORI | MCFTIMER_TMR_CLK16 |
                MCFTIMER_TMR_RESTART | MCFTIMER_TMR_ENABLE, TA(MCFTIMER_TMR));