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/clocksource.h> 20 #include <linux/errno.h> 21 #include <linux/init.h> 22 #include <linux/pci.h> 23 #include <asm/io.h> 24 25 /* Number of PMTMR ticks expected during calibration run */ 26 #define PMTMR_TICKS_PER_SEC 3579545 27 28 /* 29 * The I/O port the PMTMR resides at. 30 * The location is detected during setup_arch(), 31 * in arch/i386/acpi/boot.c 32 */ 33 u32 pmtmr_ioport __read_mostly; 34 35 #define ACPI_PM_MASK CLOCKSOURCE_MASK(24) /* limit it to 24 bits */ 36 37 static inline u32 read_pmtmr(void) 38 { 39 /* mask the output to 24 bits */ 40 return inl(pmtmr_ioport) & ACPI_PM_MASK; 41 } 42 43 static cycle_t acpi_pm_read_verified(void) 44 { 45 u32 v1 = 0, v2 = 0, v3 = 0; 46 47 /* 48 * It has been reported that because of various broken 49 * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM clock 50 * source is not latched, you must read it multiple 51 * times to ensure a safe value is read: 52 */ 53 do { 54 v1 = read_pmtmr(); 55 v2 = read_pmtmr(); 56 v3 = read_pmtmr(); 57 } while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1) 58 || (v3 > v1 && v3 < v2)); 59 60 return (cycle_t)v2; 61 } 62 63 static cycle_t acpi_pm_read(void) 64 { 65 return (cycle_t)read_pmtmr(); 66 } 67 68 static struct clocksource clocksource_acpi_pm = { 69 .name = "acpi_pm", 70 .rating = 200, 71 .read = acpi_pm_read, 72 .mask = (cycle_t)ACPI_PM_MASK, 73 .mult = 0, /*to be caluclated*/ 74 .shift = 22, 75 .is_continuous = 1, 76 }; 77 78 79 #ifdef CONFIG_PCI 80 static int acpi_pm_good; 81 static int __init acpi_pm_good_setup(char *__str) 82 { 83 acpi_pm_good = 1; 84 return 1; 85 } 86 __setup("acpi_pm_good", acpi_pm_good_setup); 87 88 static inline void acpi_pm_need_workaround(void) 89 { 90 clocksource_acpi_pm.read = acpi_pm_read_verified; 91 clocksource_acpi_pm.rating = 110; 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 __devinit acpi_pm_check_blacklist(struct pci_dev *dev) 105 { 106 u8 rev; 107 108 if (acpi_pm_good) 109 return; 110 111 pci_read_config_byte(dev, PCI_REVISION_ID, &rev); 112 /* the bug has been fixed in PIIX4M */ 113 if (rev < 3) { 114 printk(KERN_WARNING "* Found PM-Timer Bug on the chipset." 115 " Due to workarounds for a bug,\n" 116 "* this clock source is slow. Consider trying" 117 " other clock sources\n"); 118 119 acpi_pm_need_workaround(); 120 } 121 } 122 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3, 123 acpi_pm_check_blacklist); 124 125 static void __devinit acpi_pm_check_graylist(struct pci_dev *dev) 126 { 127 if (acpi_pm_good) 128 return; 129 130 printk(KERN_WARNING "* The chipset may have PM-Timer Bug. Due to" 131 " workarounds for a bug,\n" 132 "* this clock source is slow. If you are sure your timer" 133 " does not have\n" 134 "* this bug, please use \"acpi_pm_good\" to disable the" 135 " workaround\n"); 136 137 acpi_pm_need_workaround(); 138 } 139 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82801DB_0, 140 acpi_pm_check_graylist); 141 #endif 142 143 144 static int __init init_acpi_pm_clocksource(void) 145 { 146 u32 value1, value2; 147 unsigned int i; 148 149 if (!pmtmr_ioport) 150 return -ENODEV; 151 152 clocksource_acpi_pm.mult = clocksource_hz2mult(PMTMR_TICKS_PER_SEC, 153 clocksource_acpi_pm.shift); 154 155 /* "verify" this timing source: */ 156 value1 = read_pmtmr(); 157 for (i = 0; i < 10000; i++) { 158 value2 = read_pmtmr(); 159 if (value2 == value1) 160 continue; 161 if (value2 > value1) 162 goto pm_good; 163 if ((value2 < value1) && ((value2) < 0xFFF)) 164 goto pm_good; 165 printk(KERN_INFO "PM-Timer had inconsistent results:" 166 " 0x%#x, 0x%#x - aborting.\n", value1, value2); 167 return -EINVAL; 168 } 169 printk(KERN_INFO "PM-Timer had no reasonable result:" 170 " 0x%#x - aborting.\n", value1); 171 return -ENODEV; 172 173 pm_good: 174 return clocksource_register(&clocksource_acpi_pm); 175 } 176 177 module_init(init_acpi_pm_clocksource); 178