1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/drivers/clocksource/acpi_pm.c 4 * 5 * This file contains the ACPI PM based clocksource. 6 * 7 * This code was largely moved from the i386 timer_pm.c file 8 * which was (C) Dominik Brodowski <linux@brodo.de> 2003 9 * and contained the following comments: 10 * 11 * Driver to use the Power Management Timer (PMTMR) available in some 12 * southbridges as primary timing source for the Linux kernel. 13 * 14 * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c, 15 * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4. 16 */ 17 18 #include <linux/acpi_pmtmr.h> 19 #include <linux/clocksource.h> 20 #include <linux/timex.h> 21 #include <linux/errno.h> 22 #include <linux/init.h> 23 #include <linux/pci.h> 24 #include <linux/delay.h> 25 #include <asm/io.h> 26 27 /* 28 * The I/O port the PMTMR resides at. 29 * The location is detected during setup_arch(), 30 * in arch/i386/kernel/acpi/boot.c 31 */ 32 u32 pmtmr_ioport __read_mostly; 33 34 static inline u32 read_pmtmr(void) 35 { 36 /* mask the output to 24 bits */ 37 return inl(pmtmr_ioport) & ACPI_PM_MASK; 38 } 39 40 u32 acpi_pm_read_verified(void) 41 { 42 u32 v1 = 0, v2 = 0, v3 = 0; 43 44 /* 45 * It has been reported that because of various broken 46 * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM clock 47 * source is not latched, you must read it multiple 48 * times to ensure a safe value is read: 49 */ 50 do { 51 v1 = read_pmtmr(); 52 v2 = read_pmtmr(); 53 v3 = read_pmtmr(); 54 } while (unlikely((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1) 55 || (v3 > v1 && v3 < v2))); 56 57 return v2; 58 } 59 60 static u64 acpi_pm_read(struct clocksource *cs) 61 { 62 return (u64)read_pmtmr(); 63 } 64 65 static struct clocksource clocksource_acpi_pm = { 66 .name = "acpi_pm", 67 .rating = 200, 68 .read = acpi_pm_read, 69 .mask = (u64)ACPI_PM_MASK, 70 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 71 }; 72 73 74 #ifdef CONFIG_PCI 75 static int acpi_pm_good; 76 static int __init acpi_pm_good_setup(char *__str) 77 { 78 acpi_pm_good = 1; 79 return 1; 80 } 81 __setup("acpi_pm_good", acpi_pm_good_setup); 82 83 static u64 acpi_pm_read_slow(struct clocksource *cs) 84 { 85 return (u64)acpi_pm_read_verified(); 86 } 87 88 static inline void acpi_pm_need_workaround(void) 89 { 90 clocksource_acpi_pm.read = acpi_pm_read_slow; 91 clocksource_acpi_pm.rating = 120; 92 } 93 94 /* 95 * PIIX4 Errata: 96 * 97 * The power management timer may return improper results when read. 98 * Although the timer value settles properly after incrementing, 99 * while incrementing there is a 3 ns window every 69.8 ns where the 100 * timer value is indeterminate (a 4.2% chance that the data will be 101 * incorrect when read). As a result, the ACPI free running count up 102 * timer specification is violated due to erroneous reads. 103 */ 104 static void acpi_pm_check_blacklist(struct pci_dev *dev) 105 { 106 if (acpi_pm_good) 107 return; 108 109 /* the bug has been fixed in PIIX4M */ 110 if (dev->revision < 3) { 111 pr_warn("* Found PM-Timer Bug on the chipset. Due to workarounds for a bug,\n" 112 "* this clock source is slow. Consider trying other clock sources\n"); 113 114 acpi_pm_need_workaround(); 115 } 116 } 117 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3, 118 acpi_pm_check_blacklist); 119 120 static void acpi_pm_check_graylist(struct pci_dev *dev) 121 { 122 if (acpi_pm_good) 123 return; 124 125 pr_warn("* The chipset may have PM-Timer Bug. Due to workarounds for a bug,\n" 126 "* this clock source is slow. If you are sure your timer does not have\n" 127 "* this bug, please use \"acpi_pm_good\" to disable the workaround\n"); 128 129 acpi_pm_need_workaround(); 130 } 131 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82801DB_0, 132 acpi_pm_check_graylist); 133 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_LE, 134 acpi_pm_check_graylist); 135 #endif 136 137 #ifndef CONFIG_X86_64 138 #include <asm/mach_timer.h> 139 #define PMTMR_EXPECTED_RATE \ 140 ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (PIT_TICK_RATE>>10)) 141 /* 142 * Some boards have the PMTMR running way too fast. We check 143 * the PMTMR rate against PIT channel 2 to catch these cases. 144 */ 145 static int verify_pmtmr_rate(void) 146 { 147 u64 value1, value2; 148 unsigned long count, delta; 149 150 mach_prepare_counter(); 151 value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm); 152 mach_countup(&count); 153 value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm); 154 delta = (value2 - value1) & ACPI_PM_MASK; 155 156 /* Check that the PMTMR delta is within 5% of what we expect */ 157 if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 || 158 delta > (PMTMR_EXPECTED_RATE * 21) / 20) { 159 pr_info("PM-Timer running at invalid rate: %lu%% of normal - aborting.\n", 160 100UL * delta / PMTMR_EXPECTED_RATE); 161 return -1; 162 } 163 164 return 0; 165 } 166 #else 167 #define verify_pmtmr_rate() (0) 168 #endif 169 170 /* Number of monotonicity checks to perform during initialization */ 171 #define ACPI_PM_MONOTONICITY_CHECKS 10 172 /* Number of reads we try to get two different values */ 173 #define ACPI_PM_READ_CHECKS 10000 174 175 static int __init init_acpi_pm_clocksource(void) 176 { 177 u64 value1, value2; 178 unsigned int i, j = 0; 179 180 if (!pmtmr_ioport) 181 return -ENODEV; 182 183 /* "verify" this timing source: */ 184 for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) { 185 udelay(100 * j); 186 value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm); 187 for (i = 0; i < ACPI_PM_READ_CHECKS; i++) { 188 value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm); 189 if (value2 == value1) 190 continue; 191 if (value2 > value1) 192 break; 193 if ((value2 < value1) && ((value2) < 0xFFF)) 194 break; 195 pr_info("PM-Timer had inconsistent results: %#llx, %#llx - aborting.\n", 196 value1, value2); 197 pmtmr_ioport = 0; 198 return -EINVAL; 199 } 200 if (i == ACPI_PM_READ_CHECKS) { 201 pr_info("PM-Timer failed consistency check (%#llx) - aborting.\n", 202 value1); 203 pmtmr_ioport = 0; 204 return -ENODEV; 205 } 206 } 207 208 if (verify_pmtmr_rate() != 0){ 209 pmtmr_ioport = 0; 210 return -ENODEV; 211 } 212 213 return clocksource_register_hz(&clocksource_acpi_pm, 214 PMTMR_TICKS_PER_SEC); 215 } 216 217 /* We use fs_initcall because we want the PCI fixups to have run 218 * but we still need to load before device_initcall 219 */ 220 fs_initcall(init_acpi_pm_clocksource); 221 222 /* 223 * Allow an override of the IOPort. Stupid BIOSes do not tell us about 224 * the PMTimer, but we might know where it is. 225 */ 226 static int __init parse_pmtmr(char *arg) 227 { 228 unsigned int base; 229 int ret; 230 231 ret = kstrtouint(arg, 16, &base); 232 if (ret) 233 return ret; 234 235 pr_info("PMTMR IOPort override: 0x%04x -> 0x%04x\n", pmtmr_ioport, 236 base); 237 pmtmr_ioport = base; 238 239 return 1; 240 } 241 __setup("pmtmr=", parse_pmtmr); 242