Release 4.7 drivers/clocksource/acpi_pm.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;
}
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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;
}
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static cycle_t acpi_pm_read(struct clocksource *cs)
{
return (cycle_t)read_pmtmr();
}
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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 acpi_pm_good;
static int __init acpi_pm_good_setup(char *__str)
{
acpi_pm_good = 1;
return 1;
}
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__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();
}
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static inline void acpi_pm_need_workaround(void)
{
clocksource_acpi_pm.read = acpi_pm_read_slow;
clocksource_acpi_pm.rating = 120;
}
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/*
* 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 acpi_pm_check_blacklist(struct pci_dev *dev)
{
if (acpi_pm_good)
return;
/* the bug has been fixed in PIIX4M */
if (dev->revision < 3) {
pr_warn("* 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();
}
}
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| Total | 36 | 100.00% | 3 | 100.00% |
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3,
acpi_pm_check_blacklist);
static void acpi_pm_check_graylist(struct pci_dev *dev)
{
if (acpi_pm_good)
return;
pr_warn("* 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();
}
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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) {
pr_info("PM-Timer running at invalid rate: %lu%% of normal - aborting.\n",
100UL * delta / PMTMR_EXPECTED_RATE);
return -1;
}
return 0;
}
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#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;
pr_info("PM-Timer had inconsistent results: %#llx, %#llx - aborting.\n",
value1, value2);
pmtmr_ioport = 0;
return -EINVAL;
}
if (i == ACPI_PM_READ_CHECKS) {
pr_info("PM-Timer failed consistency check (%#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);
}
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/* 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 int base;
int ret;
ret = kstrtouint(arg, 16, &base);
if (ret)
return ret;
pr_info("PMTMR IOPort override: 0x%04x -> 0x%04x\n", pmtmr_ioport,
base);
pmtmr_ioport = base;
return 1;
}
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__setup("pmtmr=", parse_pmtmr);
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