[ARM PATCH] 2571/1: minor time-keeping fixes for ixp2000

Patch from Lennert Buytenhek

There are two very minor issues with time-keeping on the ixp2000:
1. It turns out that if T#_CLD (timer reload value) is set to X,
   it means the timer will spend a full tick on 0, then a full
   tick on X, and then start counting down towards 0, which then
   effectively gives the timer a period of X+1 instead of the
   intended X.  Solve by writing X-1 instead of X to T#_CLD.
   This is relatively harmless, though -- assuming a 50MHz system
   clock (like on the ENP-2611) and HZ=100, there will be 500000
   timer interrupts generated per 500001 real-world jiffies, but
   that last timer interrupt will call timer_tick twice, taking the
   system time from 499999 jiffies plus 20000 usec to 500001 jiffies
   plus 0 usec.  Every 500000th jiffy will 'not exist', and every
   other jiffy will last 10002us instead of 10000us.
2. next_jiffy_time is initialised as '0xffffffff - ticks_per_jiffy',
   but timer 4 starts ticking from 0xffffffff downwards, which will
   cause the time offset in the first 1/HZ sec after timer int init
   to be negative, and the first timer interrupt ever not to call
   timer_tick().
Neither of these issues can cause clock drift or backwards clock
motion, but it's good to fix them nevertheless.

Signed-off-by: Lennert Buytenhek
Signed-off-by: Deepak Saxena
Signed-off-by: Russell King

0 files changed, 0 insertions, 0 deletions