1 /*- 2 * ---------------------------------------------------------------------------- 3 * "THE BEER-WARE LICENSE" (Revision 42): 4 * <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you 5 * can do whatever you want with this stuff. If we meet some day, and you think 6 * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp 7 * ---------------------------------------------------------------------------- 8 */ 9 10 #include <sys/cdefs.h> 11 __FBSDID("$FreeBSD$"); 12 13 /*- 14 * Just when we thought life were beautiful, reality pops its grim face over 15 * the edge again: 16 * 17 * ] 20. ACPI Timer Errata 18 * ] 19 * ] Problem: The power management timer may return improper result when 20 * ] read. Although the timer value settles properly after incrementing, 21 * ] while incrementing there is a 3nS window every 69.8nS where the 22 * ] timer value is indeterminate (a 4.2% chance that the data will be 23 * ] incorrect when read). As a result, the ACPI free running count up 24 * ] timer specification is violated due to erroneous reads. Implication: 25 * ] System hangs due to the "inaccuracy" of the timer when used by 26 * ] software for time critical events and delays. 27 * ] 28 * ] Workaround: Read the register twice and compare. 29 * ] Status: This will not be fixed in the PIIX4 or PIIX4E. 30 * 31 * The counter is in other words not latched to the PCI bus clock when 32 * read. Notice the workaround isn't: We need to read until we have 33 * three monotonic samples and then use the middle one, otherwise we are 34 * not protected against the fact that the bits can be wrong in two 35 * directions. If we only cared about monosity two reads would be enough. 36 */ 37 38 /* #include "opt_bus.h" */ 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/timetc.h> 43 #include <sys/kernel.h> 44 #include <sys/module.h> 45 #include <sys/sysctl.h> 46 #include <sys/bus.h> 47 48 #include <dev/pci/pcireg.h> 49 #include <dev/pci/pcivar.h> 50 51 static unsigned piix_get_timecount(struct timecounter *tc); 52 53 static u_int32_t piix_timecounter_address; 54 static u_int piix_freq = 14318182/4; 55 56 static struct timecounter piix_timecounter = { 57 piix_get_timecount, /* get_timecount */ 58 0, /* no poll_pps */ 59 0xffffff, /* counter_mask */ 60 0, /* frequency */ 61 "PIIX" /* name */ 62 }; 63 64 65 static int 66 sysctl_machdep_piix_freq(SYSCTL_HANDLER_ARGS) 67 { 68 int error; 69 u_int freq; 70 71 if (piix_timecounter.tc_frequency == 0) 72 return (EOPNOTSUPP); 73 freq = piix_freq; 74 error = sysctl_handle_int(oidp, &freq, 0, req); 75 if (error == 0 && req->newptr != NULL) { 76 piix_freq = freq; 77 piix_timecounter.tc_frequency = piix_freq; 78 } 79 return (error); 80 } 81 82 SYSCTL_PROC(_machdep, OID_AUTO, piix_freq, CTLTYPE_INT | CTLFLAG_RW, 83 0, sizeof(u_int), sysctl_machdep_piix_freq, "I", ""); 84 85 static unsigned 86 piix_get_timecount(struct timecounter *tc) 87 { 88 unsigned u1, u2, u3; 89 90 u2 = inl(piix_timecounter_address); 91 u3 = inl(piix_timecounter_address); 92 do { 93 u1 = u2; 94 u2 = u3; 95 u3 = inl(piix_timecounter_address); 96 } while (u1 > u2 || u2 > u3); 97 return (u2); 98 } 99 100 static int 101 piix_probe(device_t dev) 102 { 103 u_int32_t d; 104 105 if (devclass_get_device(devclass_find("acpi"), 0) != NULL) 106 return (ENXIO); 107 switch (pci_get_devid(dev)) { 108 case 0x71138086: 109 device_set_desc(dev, "PIIX Timecounter"); 110 break; 111 default: 112 return (ENXIO); 113 } 114 115 d = pci_read_config(dev, PCIR_COMMAND, 2); 116 if (!(d & PCIM_CMD_PORTEN)) { 117 device_printf(dev, "PIIX I/O space not mapped\n"); 118 return (ENXIO); 119 } 120 return (0); 121 } 122 123 static int 124 piix_attach(device_t dev) 125 { 126 u_int32_t d; 127 128 d = pci_read_config(dev, 0x40, 4); 129 piix_timecounter_address = (d & 0xffc0) + 8; 130 piix_timecounter.tc_frequency = piix_freq; 131 tc_init(&piix_timecounter); 132 return (0); 133 } 134 135 static device_method_t piix_methods[] = { 136 /* Device interface */ 137 DEVMETHOD(device_probe, piix_probe), 138 DEVMETHOD(device_attach, piix_attach), 139 { 0, 0 } 140 }; 141 142 static driver_t piix_driver = { 143 "piix", 144 piix_methods, 145 1, 146 }; 147 148 static devclass_t piix_devclass; 149 150 DRIVER_MODULE(piix, pci, piix_driver, piix_devclass, 0, 0); 151