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[PATCH] time: re-add verify_pmtmr_rate

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This patch re-adds the verify_pmtmr_rate functionality from 2.6.17 that
I dropped 2.6.18.

This resolves problems seen on older K6 ASUS boards where the ACPI PM
timer runs too fast.

See:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=211902
http://bugme.osdl.org/show_bug.cgi?id=2375

Thanks to Ian Campbell for re-reporting this and testing the fix!

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Ian Campbell <ijc@hellion.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
john stultz 2006-12-08 02:36:02 -08:00 committed by Linus Torvalds
parent a2ee8649ba
commit 562f9c574e
1 changed files with 36 additions and 0 deletions
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36
drivers/clocksource/acpi_pm.c
View file

@ -142,6 +142,39 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_LE,
acpi_pm_check_graylist);
#endif
#ifndef CONFIG_X86_64
#include "mach_timer.h"
#define PMTMR_EXPECTED_RATE \
((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
/*
* Some boards have the PMTMR running way too fast. We check
* the PMTMR rate against PIT channel 2 to catch these cases.
*/
static int verify_pmtmr_rate(void)
{
u32 value1, value2;
unsigned long count, delta;
mach_prepare_counter();
value1 = read_pmtmr();
mach_countup(&count);
value2 = read_pmtmr();
delta = (value2 - value1) & ACPI_PM_MASK;
/* Check that the PMTMR delta is within 5% of what we expect */
if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
printk(KERN_INFO "PM-Timer running at invalid rate: %lu%% "
"of normal - aborting.\n",
100UL * delta / PMTMR_EXPECTED_RATE);
return -1;
}
return 0;
}
#else
#define verify_pmtmr_rate() (0)
#endif
static int __init init_acpi_pm_clocksource(void)
{
@ -173,6 +206,9 @@ static int __init init_acpi_pm_clocksource(void)
return -ENODEV;
pm_good:
if (verify_pmtmr_rate() != 0)
return -ENODEV;
return clocksource_register(&clocksource_acpi_pm);
}