From: Herbert Poetzl <herbert@13thfloor.at>
hopefully 'better' fix for broken Intel Mercury/Neptune in
wait_8254_wraparound() ...
Rationale:
changing HZ to higher values (like 5k,10k or 20k) will hang machines using
wait_8254_wraparound() indefinitely, because a suboptimal workaround for
buggy Intel Mercury/Neptune chipsets is in place.
this was tested on several machines, unfortunately none with a broken Intel
Mercury/Neptune chipset, and it works fine with various HZ values ...
Signed-off-by: Herbert Pötzl <herbert@13thfloor.at>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/arch/i386/kernel/apic.c | 15 +++++----------
1 files changed, 5 insertions(+), 10 deletions(-)
diff -puN arch/i386/kernel/apic.c~improved-wait_8254_wraparound arch/i386/kernel/apic.c
--- 25/arch/i386/kernel/apic.c~improved-wait_8254_wraparound Thu Jan 6 15:37:42 2005
+++ 25-akpm/arch/i386/kernel/apic.c Thu Jan 6 15:37:42 2005
@@ -877,23 +877,18 @@ static unsigned int __init get_8254_time
/* next tick in 8254 can be caught by catching timer wraparound */
static void __init wait_8254_wraparound(void)
{
- unsigned int curr_count, prev_count=~0;
- int delta;
+ unsigned int curr_count, prev_count;
curr_count = get_8254_timer_count();
-
do {
prev_count = curr_count;
curr_count = get_8254_timer_count();
- delta = curr_count-prev_count;
- /*
- * This limit for delta seems arbitrary, but it isn't, it's
- * slightly above the level of error a buggy Mercury/Neptune
- * chipset timer can cause.
- */
+ /* workaround for broken Mercury/Neptune */
+ if (prev_count >= curr_count + 0x100)
+ curr_count = get_8254_timer_count();
- } while (delta < 300);
+ } while (prev_count >= curr_count);
}
/*
_