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Revert "clocksource: Load the ACPI PM clocksource asynchronously" 

This reverts commit b519508298.

The reason for this revert is that making the frequency verification
preemptible and interruptible is not working reliably. Michaels
machine failed to use PM-timer with the message:

  PM-Timer running at invalid rate: 113% of normal - aborting.

That's not a surprise as the frequency verification does rely on
interrupts being disabled. With a async scheduled thread there is no
guarantee to achieve the same result. Also some driver might fiddle
with the CTC channel 2 during the verification period, which makes the
result even more random and unpredictable.

This can be solved by using the same mechanism as we use in the
deferred TSC validation code, but that only will work if we verified a
working HPET _BEFORE_ trying to do the PM-Timer lazy validation.

So for now reverting is the safe option.

Bisected-by: Michael Witten <mfwitten@gmail.com>
Cc: Arjan van de Ven <arjanvandeven@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Len Brown <lenb@kernel.org>
LKML-Reference: <alpine.LFD.2.02.1204112303270.2542@ionos>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2012-04-11 23:49:16 +02:00
parent fa4da365bc
commit d48fc63f6f
1 changed files with 8 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
drivers/clocksource/acpi_pm.c
View File

@ -23,7 +23,6 @@
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/delay.h>
#include <linux/async.h>
#include <asm/io.h>
/*
@ -180,15 +179,17 @@ static int verify_pmtmr_rate(void)
/* Number of reads we try to get two different values */
#define ACPI_PM_READ_CHECKS 10000
static void __init acpi_pm_clocksource_async(void *unused, async_cookie_t cookie)
static int __init init_acpi_pm_clocksource(void)
{
cycle_t value1, value2;
unsigned int i, j = 0;
if (!pmtmr_ioport)
return -ENODEV;
/* "verify" this timing source: */
for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) {
usleep_range(100 * j, 100 * j + 100);
udelay(100 * j);
value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
for (i = 0; i < ACPI_PM_READ_CHECKS; i++) {
value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
@ -202,34 +203,25 @@ static void __init acpi_pm_clocksource_async(void *unused, async_cookie_t cookie
" 0x%#llx, 0x%#llx - aborting.\n",
value1, value2);
pmtmr_ioport = 0;
return;
return -EINVAL;
}
if (i == ACPI_PM_READ_CHECKS) {
printk(KERN_INFO "PM-Timer failed consistency check "
" (0x%#llx) - aborting.\n", value1);
pmtmr_ioport = 0;
return;
return -ENODEV;
}
}
if (verify_pmtmr_rate() != 0){
pmtmr_ioport = 0;
return;
return -ENODEV;
}
clocksource_register_hz(&clocksource_acpi_pm,
return clocksource_register_hz(&clocksource_acpi_pm,
PMTMR_TICKS_PER_SEC);
}
static int __init init_acpi_pm_clocksource(void)
{
if (!pmtmr_ioport)
return -ENODEV;
async_schedule(acpi_pm_clocksource_async, NULL);
return 0;
}
/* We use fs_initcall because we want the PCI fixups to have run
* but we still need to load before device_initcall
*/