acpi_pm.c
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/*
* 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/clocksource.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <asm/io.h>
/* Number of PMTMR ticks expected during calibration run */
#define PMTMR_TICKS_PER_SEC 3579545
/*
* The I/O port the PMTMR resides at.
* The location is detected during setup_arch(),
* in arch/i386/acpi/boot.c
*/
u32 pmtmr_ioport __read_mostly;
#define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */
static inline u32 read_pmtmr(void)
{
/* mask the output to 24 bits */
return inl(pmtmr_ioport) & ACPI_PM_MASK;
}
static cycle_t 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 ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
|| (v3 > v1 && v3 < v2));
return (cycle_t)v2;
}
static cycle_t acpi_pm_read(void)
{
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,
.mult = 0, /*to be caluclated*/
.shift = 22,
.is_continuous = 1,
};
#ifdef CONFIG_PCI
static int 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 inline void acpi_pm_need_workaround(void)
{
clocksource_acpi_pm.read = acpi_pm_read_verified;
clocksource_acpi_pm.rating = 110;
}
/*
* 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)
{
u8 rev;
if (acpi_pm_good)
return;
pci_read_config_byte(dev, PCI_REVISION_ID, &rev);
/* the bug has been fixed in PIIX4M */
if (rev < 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);
#endif
static int __init init_acpi_pm_clocksource(void)
{
u32 value1, value2;
unsigned int i;
if (!pmtmr_ioport)
return -ENODEV;
clocksource_acpi_pm.mult = clocksource_hz2mult(PMTMR_TICKS_PER_SEC,
clocksource_acpi_pm.shift);
/* "verify" this timing source: */
value1 = read_pmtmr();
for (i = 0; i < 10000; i++) {
value2 = read_pmtmr();
if (value2 == value1)
continue;
if (value2 > value1)
goto pm_good;
if ((value2 < value1) && ((value2) < 0xFFF))
goto pm_good;
printk(KERN_INFO "PM-Timer had inconsistent results:"
" 0x%#x, 0x%#x - aborting.\n", value1, value2);
return -EINVAL;
}
printk(KERN_INFO "PM-Timer had no reasonable result:"
" 0x%#x - aborting.\n", value1);
return -ENODEV;
pm_good:
return clocksource_register(&clocksource_acpi_pm);
}
module_init(init_acpi_pm_clocksource);