[POWERPC] spusched: Fix timeslice calculations

The current timeslice code mixes 'jiffies' up with 'spesched ticks'. This
change correctly defines the number of time slices each SPE contexts is
given, and clarifies the comment.

This brings the default timeslice for SPE contexts into a reasonable
range.
Signed-off-by: NJeremy Kerr <jk@ozlabs.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/platforms/cell/spufs/sched.c

@@ -70,11 +70,11 @@ static struct timer_list spusched_timer;
 /*
  * These are the 'tuning knobs' of the scheduler:
  *
- * Minimum timeslice is 5 msecs (or 10 jiffies, whichever is larger),
- * default timeslice is 100 msecs, maximum timeslice is 800 msecs.
+ * Minimum timeslice is 5 msecs (or 1 spu scheduler tick, whichever is
+ * larger), default timeslice is 100 msecs, maximum timeslice is 800 msecs.
  */
-#define MIN_SPU_TIMESLICE	max(5 * HZ / 100, 10)
-#define DEF_SPU_TIMESLICE	(100 * HZ / 100)
+#define MIN_SPU_TIMESLICE	max(5 * HZ / (1000 * SPUSCHED_TICK), 1)
+#define DEF_SPU_TIMESLICE	(100 * HZ / (1000 * SPUSCHED_TICK))
 
 #define MAX_USER_PRIO		(MAX_PRIO - MAX_RT_PRIO)
 #define SCALE_PRIO(x, prio) \