// SPDX-License-Identifier: GPL-2.0-only /* * 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 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. */ #include #include #include #include #include #include #include #include #include /* * 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 u64 acpi_pm_read(struct clocksource *cs) { return (u64)read_pmtmr(); } static struct clocksource clocksource_acpi_pm = { .name = "acpi_pm", .rating = 200, .read = acpi_pm_read, .mask = (u64)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; } __setup("acpi_pm_good", acpi_pm_good_setup); static u64 acpi_pm_read_slow(struct clocksource *cs) { return (u64)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 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(); } } 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(); } 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 #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) { u64 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; } #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) { u64 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; } if (tsc_clocksource_watchdog_disabled()) clocksource_acpi_pm.flags |= CLOCK_SOURCE_MUST_VERIFY; 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 int base; int ret; ret = kstrtouint(arg, 16, &base); if (ret) { pr_warn("PMTMR: invalid 'pmtmr=' value: '%s'\n", arg); return 1; } pr_info("PMTMR IOPort override: 0x%04x -> 0x%04x\n", pmtmr_ioport, base); pmtmr_ioport = base; return 1; } __setup("pmtmr=", parse_pmtmr);