1 /*- 2 * SPDX-License-Identifier: Beerware 3 * 4 * ---------------------------------------------------------------------------- 5 * "THE BEER-WARE LICENSE" (Revision 42): 6 * <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you 7 * can do whatever you want with this stuff. If we meet some day, and you think 8 * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp 9 * ---------------------------------------------------------------------------- 10 */ 11 12 #include <sys/cdefs.h> 13 __FBSDID("$FreeBSD$"); 14 15 /*- 16 * Just when we thought life were beautiful, reality pops its grim face over 17 * the edge again: 18 * 19 * ] 20. ACPI Timer Errata 20 * ] 21 * ] Problem: The power management timer may return improper result when 22 * ] read. Although the timer value settles properly after incrementing, 23 * ] while incrementing there is a 3nS window every 69.8nS where the 24 * ] timer value is indeterminate (a 4.2% chance that the data will be 25 * ] incorrect when read). As a result, the ACPI free running count up 26 * ] timer specification is violated due to erroneous reads. Implication: 27 * ] System hangs due to the "inaccuracy" of the timer when used by 28 * ] software for time critical events and delays. 29 * ] 30 * ] Workaround: Read the register twice and compare. 31 * ] Status: This will not be fixed in the PIIX4 or PIIX4E. 32 * 33 * The counter is in other words not latched to the PCI bus clock when 34 * read. Notice the workaround isn't: We need to read until we have 35 * three monotonic samples and then use the middle one, otherwise we are 36 * not protected against the fact that the bits can be wrong in two 37 * directions. If we only cared about monosity two reads would be enough. 38 */ 39 40 /* #include "opt_bus.h" */ 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/timetc.h> 45 #include <sys/kernel.h> 46 #include <sys/module.h> 47 #include <sys/sysctl.h> 48 #include <sys/bus.h> 49 50 #include <dev/pci/pcireg.h> 51 #include <dev/pci/pcivar.h> 52 53 static unsigned piix_get_timecount(struct timecounter *tc); 54 55 static u_int32_t piix_timecounter_address; 56 static u_int piix_freq = 14318182/4; 57 58 static struct timecounter piix_timecounter = { 59 piix_get_timecount, /* get_timecount */ 60 0, /* no poll_pps */ 61 0xffffff, /* counter_mask */ 62 0, /* frequency */ 63 "PIIX" /* name */ 64 }; 65 66 static int 67 sysctl_machdep_piix_freq(SYSCTL_HANDLER_ARGS) 68 { 69 int error; 70 u_int freq; 71 72 if (piix_timecounter.tc_frequency == 0) 73 return (EOPNOTSUPP); 74 freq = piix_freq; 75 error = sysctl_handle_int(oidp, &freq, 0, req); 76 if (error == 0 && req->newptr != NULL) { 77 piix_freq = freq; 78 piix_timecounter.tc_frequency = piix_freq; 79 } 80 return (error); 81 } 82 83 SYSCTL_PROC(_machdep, OID_AUTO, piix_freq, 84 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 0, sizeof(u_int), 85 sysctl_machdep_piix_freq, "I", 86 ""); 87 88 static unsigned 89 piix_get_timecount(struct timecounter *tc) 90 { 91 unsigned u1, u2, u3; 92 93 u2 = inl(piix_timecounter_address); 94 u3 = inl(piix_timecounter_address); 95 do { 96 u1 = u2; 97 u2 = u3; 98 u3 = inl(piix_timecounter_address); 99 } while (u1 > u2 || u2 > u3); 100 return (u2); 101 } 102 103 static int 104 piix_probe(device_t dev) 105 { 106 u_int32_t d; 107 108 if (devclass_get_device(devclass_find("acpi"), 0) != NULL) 109 return (ENXIO); 110 switch (pci_get_devid(dev)) { 111 case 0x71138086: 112 device_set_desc(dev, "PIIX Timecounter"); 113 break; 114 default: 115 return (ENXIO); 116 } 117 118 d = pci_read_config(dev, PCIR_COMMAND, 2); 119 if (!(d & PCIM_CMD_PORTEN)) { 120 device_printf(dev, "PIIX I/O space not mapped\n"); 121 return (ENXIO); 122 } 123 return (0); 124 } 125 126 static int 127 piix_attach(device_t dev) 128 { 129 u_int32_t d; 130 131 d = pci_read_config(dev, 0x40, 4); 132 piix_timecounter_address = (d & 0xffc0) + 8; 133 piix_timecounter.tc_frequency = piix_freq; 134 tc_init(&piix_timecounter); 135 return (0); 136 } 137 138 static device_method_t piix_methods[] = { 139 /* Device interface */ 140 DEVMETHOD(device_probe, piix_probe), 141 DEVMETHOD(device_attach, piix_attach), 142 { 0, 0 } 143 }; 144 145 static driver_t piix_driver = { 146 "piix", 147 piix_methods, 148 1, 149 }; 150 151 DRIVER_MODULE(piix, pci, piix_driver, 0, 0); 152