diff options
Diffstat (limited to 'drivers/clocksource/acpi_pm.c')
| -rw-r--r-- | drivers/clocksource/acpi_pm.c | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c new file mode 100644 index 000000000000..7ad3be8c0f49 --- /dev/null +++ b/drivers/clocksource/acpi_pm.c @@ -0,0 +1,177 @@ +/* + * 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 CLOCKSOURCE_MASK(24) /* 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); |