From: Herbert Poetzl <herbert@13thfloor.at>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>, Pavel Machek <pavel@ucw.cz>
Subject: improved wait_8254_wraparound()
Date: Thu, 6 Jan 2005 10:19:05 +0100 [thread overview]
Message-ID: <20050106091903.GC728@mail.13thfloor.at> (raw)
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 ...
please consider for inclusion or further testing ...
TIA,
Herbert
Signed-off-by: Herbert Pötzl <herbert@13thfloor.at>
diff -NurpP --minimal
--- linux-2.6.10/arch/i386/kernel/apic.c 2004-12-25 01:54:43.000000000 +0100
+++ linux-2.6.10-fixed/arch/i386/kernel/apic.c 2005-01-02 10:57:33.000000000 +0100
@@ -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);
}
/*
reply other threads:[~2005-01-06 9:19 UTC|newest]
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