linux/drivers/clocksource/acpi_pm.c
Thomas Gleixner d48fc63f6f 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>
2012-04-12 00:05:05 +02:00

250 lines
6.5 KiB
C

/*
* linux/drivers/clocksource/acpi_pm.c
*
* This file contains the ACPI PM based clocksource.
*
* This code was largely moved from the i386 timer_pm.c file
* which was (C) Dominik Brodowski <linux@brodo.de> 2003
* and contained the following comments:
*
* Driver to use the Power Management Timer (PMTMR) available in some
* southbridges as primary timing source for the Linux kernel.
*
* Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
* timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
*
* This file is licensed under the GPL v2.
*/
#include <linux/acpi_pmtmr.h>
#include <linux/clocksource.h>
#include <linux/timex.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/delay.h>
#include <asm/io.h>
/*
* The I/O port the PMTMR resides at.
* The location is detected during setup_arch(),
* in arch/i386/kernel/acpi/boot.c
*/
u32 pmtmr_ioport __read_mostly;
static inline u32 read_pmtmr(void)
{
/* mask the output to 24 bits */
return inl(pmtmr_ioport) & ACPI_PM_MASK;
}
u32 acpi_pm_read_verified(void)
{
u32 v1 = 0, v2 = 0, v3 = 0;
/*
* It has been reported that because of various broken
* chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM clock
* source is not latched, you must read it multiple
* times to ensure a safe value is read:
*/
do {
v1 = read_pmtmr();
v2 = read_pmtmr();
v3 = read_pmtmr();
} while (unlikely((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
|| (v3 > v1 && v3 < v2)));
return v2;
}
static cycle_t acpi_pm_read(struct clocksource *cs)
{
return (cycle_t)read_pmtmr();
}
static struct clocksource clocksource_acpi_pm = {
.name = "acpi_pm",
.rating = 200,
.read = acpi_pm_read,
.mask = (cycle_t)ACPI_PM_MASK,
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
#ifdef CONFIG_PCI
static int __devinitdata acpi_pm_good;
static int __init acpi_pm_good_setup(char *__str)
{
acpi_pm_good = 1;
return 1;
}
__setup("acpi_pm_good", acpi_pm_good_setup);
static cycle_t acpi_pm_read_slow(struct clocksource *cs)
{
return (cycle_t)acpi_pm_read_verified();
}
static inline void acpi_pm_need_workaround(void)
{
clocksource_acpi_pm.read = acpi_pm_read_slow;
clocksource_acpi_pm.rating = 120;
}
/*
* PIIX4 Errata:
*
* The power management timer may return improper results when read.
* Although the timer value settles properly after incrementing,
* while incrementing there is a 3 ns window every 69.8 ns where the
* timer value is indeterminate (a 4.2% chance that the data will be
* incorrect when read). As a result, the ACPI free running count up
* timer specification is violated due to erroneous reads.
*/
static void __devinit acpi_pm_check_blacklist(struct pci_dev *dev)
{
if (acpi_pm_good)
return;
/* the bug has been fixed in PIIX4M */
if (dev->revision < 3) {
printk(KERN_WARNING "* Found PM-Timer Bug on the chipset."
" Due to workarounds for a bug,\n"
"* this clock source is slow. Consider trying"
" other clock sources\n");
acpi_pm_need_workaround();
}
}
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3,
acpi_pm_check_blacklist);
static void __devinit acpi_pm_check_graylist(struct pci_dev *dev)
{
if (acpi_pm_good)
return;
printk(KERN_WARNING "* The chipset may have PM-Timer Bug. Due to"
" workarounds for a bug,\n"
"* this clock source is slow. If you are sure your timer"
" does not have\n"
"* this bug, please use \"acpi_pm_good\" to disable the"
" workaround\n");
acpi_pm_need_workaround();
}
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82801DB_0,
acpi_pm_check_graylist);
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_LE,
acpi_pm_check_graylist);
#endif
#ifndef CONFIG_X86_64
#include <asm/mach_timer.h>
#define PMTMR_EXPECTED_RATE \
((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (PIT_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)
{
cycle_t value1, value2;
unsigned long count, delta;
mach_prepare_counter();
value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
mach_countup(&count);
value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
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
/* Number of monotonicity checks to perform during initialization */
#define ACPI_PM_MONOTONICITY_CHECKS 10
/* Number of reads we try to get two different values */
#define ACPI_PM_READ_CHECKS 10000
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++) {
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);
if (value2 == value1)
continue;
if (value2 > value1)
break;
if ((value2 < value1) && ((value2) < 0xFFF))
break;
printk(KERN_INFO "PM-Timer had inconsistent results:"
" 0x%#llx, 0x%#llx - aborting.\n",
value1, value2);
pmtmr_ioport = 0;
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 -ENODEV;
}
}
if (verify_pmtmr_rate() != 0){
pmtmr_ioport = 0;
return -ENODEV;
}
return clocksource_register_hz(&clocksource_acpi_pm,
PMTMR_TICKS_PER_SEC);
}
/* We use fs_initcall because we want the PCI fixups to have run
* but we still need to load before device_initcall
*/
fs_initcall(init_acpi_pm_clocksource);
/*
* Allow an override of the IOPort. Stupid BIOSes do not tell us about
* the PMTimer, but we might know where it is.
*/
static int __init parse_pmtmr(char *arg)
{
unsigned long base;
if (strict_strtoul(arg, 16, &base))
return -EINVAL;
#ifdef CONFIG_X86_64
if (base > UINT_MAX)
return -ERANGE;
#endif
printk(KERN_INFO "PMTMR IOPort override: 0x%04x -> 0x%04lx\n",
pmtmr_ioport, base);
pmtmr_ioport = base;
return 1;
}
__setup("pmtmr=", parse_pmtmr);