1 /* 2 * linux/drivers/clocksource/acpi_pm.c 3 * 4 * This file contains the ACPI PM based clocksource. 5 * 6 * This code was largely moved from the i386 timer_pm.c file 7 * which was (C) Dominik Brodowski <linux@brodo.de> 2003 8 * and contained the following comments: 9 * 10 * Driver to use the Power Management Timer (PMTMR) available in some 11 * southbridges as primary timing source for the Linux kernel. 12 * 13 * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c, 14 * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4. 15 * 16 * This file is licensed under the GPL v2. 17 */ 18 19 #include <linux/acpi_pmtmr.h> 20 #include <linux/clocksource.h> 21 #include <linux/timex.h> 22 #include <linux/errno.h> 23 #include <linux/init.h> 24 #include <linux/pci.h> 25 #include <linux/delay.h> 26 #include <asm/io.h> 27 28 /* 29 * The I/O port the PMTMR resides at. 30 * The location is detected during setup_arch(), 31 * in arch/i386/kernel/acpi/boot.c 32 */ 33 u32 pmtmr_ioport __read_mostly; 34 35 static inline u32 read_pmtmr(void) 36 { 37 /* mask the output to 24 bits */ 38 return inl(pmtmr_ioport) & ACPI_PM_MASK; 39 } 40 41 u32 acpi_pm_read_verified(void) 42 { 43 u32 v1 = 0, v2 = 0, v3 = 0; 44 45 /* 46 * It has been reported that because of various broken 47 * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM clock 48 * source is not latched, you must read it multiple 49 * times to ensure a safe value is read: 50 */ 51 do { 52 v1 = read_pmtmr(); 53 v2 = read_pmtmr(); 54 v3 = read_pmtmr(); 55 } while (unlikely((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1) 56 || (v3 > v1 && v3 < v2))); 57 58 return v2; 59 } 60 61 static cycle_t acpi_pm_read(struct clocksource *cs) 62 { 63 return (cycle_t)read_pmtmr(); 64 } 65 66 static struct clocksource clocksource_acpi_pm = { 67 .name = "acpi_pm", 68 .rating = 200, 69 .read = acpi_pm_read, 70 .mask = (cycle_t)ACPI_PM_MASK, 71 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 72 }; 73 74 75 #ifdef CONFIG_PCI 76 static int acpi_pm_good; 77 static int __init acpi_pm_good_setup(char *__str) 78 { 79 acpi_pm_good = 1; 80 return 1; 81 } 82 __setup("acpi_pm_good", acpi_pm_good_setup); 83 84 static cycle_t acpi_pm_read_slow(struct clocksource *cs) 85 { 86 return (cycle_t)acpi_pm_read_verified(); 87 } 88 89 static inline void acpi_pm_need_workaround(void) 90 { 91 clocksource_acpi_pm.read = acpi_pm_read_slow; 92 clocksource_acpi_pm.rating = 120; 93 } 94 95 /* 96 * PIIX4 Errata: 97 * 98 * The power management timer may return improper results when read. 99 * Although the timer value settles properly after incrementing, 100 * while incrementing there is a 3 ns window every 69.8 ns where the 101 * timer value is indeterminate (a 4.2% chance that the data will be 102 * incorrect when read). As a result, the ACPI free running count up 103 * timer specification is violated due to erroneous reads. 104 */ 105 static void acpi_pm_check_blacklist(struct pci_dev *dev) 106 { 107 if (acpi_pm_good) 108 return; 109 110 /* the bug has been fixed in PIIX4M */ 111 if (dev->revision < 3) { 112 printk(KERN_WARNING "* Found PM-Timer Bug on the chipset." 113 " Due to workarounds for a bug,\n" 114 "* this clock source is slow. Consider trying" 115 " other clock sources\n"); 116 117 acpi_pm_need_workaround(); 118 } 119 } 120 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3, 121 acpi_pm_check_blacklist); 122 123 static void acpi_pm_check_graylist(struct pci_dev *dev) 124 { 125 if (acpi_pm_good) 126 return; 127 128 printk(KERN_WARNING "* The chipset may have PM-Timer Bug. Due to" 129 " workarounds for a bug,\n" 130 "* this clock source is slow. If you are sure your timer" 131 " does not have\n" 132 "* this bug, please use \"acpi_pm_good\" to disable the" 133 " workaround\n"); 134 135 acpi_pm_need_workaround(); 136 } 137 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82801DB_0, 138 acpi_pm_check_graylist); 139 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_LE, 140 acpi_pm_check_graylist); 141 #endif 142 143 #ifndef CONFIG_X86_64 144 #include <asm/mach_timer.h> 145 #define PMTMR_EXPECTED_RATE \ 146 ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (PIT_TICK_RATE>>10)) 147 /* 148 * Some boards have the PMTMR running way too fast. We check 149 * the PMTMR rate against PIT channel 2 to catch these cases. 150 */ 151 static int verify_pmtmr_rate(void) 152 { 153 cycle_t value1, value2; 154 unsigned long count, delta; 155 156 mach_prepare_counter(); 157 value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm); 158 mach_countup(&count); 159 value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm); 160 delta = (value2 - value1) & ACPI_PM_MASK; 161 162 /* Check that the PMTMR delta is within 5% of what we expect */ 163 if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 || 164 delta > (PMTMR_EXPECTED_RATE * 21) / 20) { 165 printk(KERN_INFO "PM-Timer running at invalid rate: %lu%% " 166 "of normal - aborting.\n", 167 100UL * delta / PMTMR_EXPECTED_RATE); 168 return -1; 169 } 170 171 return 0; 172 } 173 #else 174 #define verify_pmtmr_rate() (0) 175 #endif 176 177 /* Number of monotonicity checks to perform during initialization */ 178 #define ACPI_PM_MONOTONICITY_CHECKS 10 179 /* Number of reads we try to get two different values */ 180 #define ACPI_PM_READ_CHECKS 10000 181 182 static int __init init_acpi_pm_clocksource(void) 183 { 184 cycle_t value1, value2; 185 unsigned int i, j = 0; 186 187 if (!pmtmr_ioport) 188 return -ENODEV; 189 190 /* "verify" this timing source: */ 191 for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) { 192 udelay(100 * j); 193 value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm); 194 for (i = 0; i < ACPI_PM_READ_CHECKS; i++) { 195 value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm); 196 if (value2 == value1) 197 continue; 198 if (value2 > value1) 199 break; 200 if ((value2 < value1) && ((value2) < 0xFFF)) 201 break; 202 printk(KERN_INFO "PM-Timer had inconsistent results:" 203 " %#llx, %#llx - aborting.\n", 204 value1, value2); 205 pmtmr_ioport = 0; 206 return -EINVAL; 207 } 208 if (i == ACPI_PM_READ_CHECKS) { 209 printk(KERN_INFO "PM-Timer failed consistency check " 210 " (%#llx) - aborting.\n", value1); 211 pmtmr_ioport = 0; 212 return -ENODEV; 213 } 214 } 215 216 if (verify_pmtmr_rate() != 0){ 217 pmtmr_ioport = 0; 218 return -ENODEV; 219 } 220 221 return clocksource_register_hz(&clocksource_acpi_pm, 222 PMTMR_TICKS_PER_SEC); 223 } 224 225 /* We use fs_initcall because we want the PCI fixups to have run 226 * but we still need to load before device_initcall 227 */ 228 fs_initcall(init_acpi_pm_clocksource); 229 230 /* 231 * Allow an override of the IOPort. Stupid BIOSes do not tell us about 232 * the PMTimer, but we might know where it is. 233 */ 234 static int __init parse_pmtmr(char *arg) 235 { 236 unsigned int base; 237 int ret; 238 239 ret = kstrtouint(arg, 16, &base); 240 if (ret) 241 return ret; 242 243 pr_info("PMTMR IOPort override: 0x%04x -> 0x%04x\n", pmtmr_ioport, 244 base); 245 pmtmr_ioport = base; 246 247 return 1; 248 } 249 __setup("pmtmr=", parse_pmtmr); 250