151 lines
3.9 KiB
C
151 lines
3.9 KiB
C
/*-
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* ----------------------------------------------------------------------------
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* "THE BEER-WARE LICENSE" (Revision 42):
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* <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
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* can do whatever you want with this stuff. If we meet some day, and you think
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* this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
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* ----------------------------------------------------------------------------
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/*-
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* Just when we thought life were beautiful, reality pops its grim face over
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* the edge again:
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*
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* ] 20. ACPI Timer Errata
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* ]
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* ] Problem: The power management timer may return improper result when
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* ] read. Although the timer value settles properly after incrementing,
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* ] while incrementing there is a 3nS window every 69.8nS where the
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* ] timer value is indeterminate (a 4.2% chance that the data will be
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* ] incorrect when read). As a result, the ACPI free running count up
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* ] timer specification is violated due to erroneous reads. Implication:
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* ] System hangs due to the "inaccuracy" of the timer when used by
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* ] software for time critical events and delays.
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* ]
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* ] Workaround: Read the register twice and compare.
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* ] Status: This will not be fixed in the PIIX4 or PIIX4E.
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*
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* The counter is in other words not latched to the PCI bus clock when
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* read. Notice the workaround isn't: We need to read until we have
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* three monotonic samples and then use the middle one, otherwise we are
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* not protected against the fact that the bits can be wrong in two
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* directions. If we only cared about monosity two reads would be enough.
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*/
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/* #include "opt_bus.h" */
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/timetc.h>
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#include <sys/kernel.h>
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#include <sys/module.h>
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#include <sys/sysctl.h>
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#include <sys/bus.h>
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#include <dev/pci/pcireg.h>
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#include <dev/pci/pcivar.h>
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static unsigned piix_get_timecount(struct timecounter *tc);
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static u_int32_t piix_timecounter_address;
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static u_int piix_freq = 14318182/4;
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static struct timecounter piix_timecounter = {
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piix_get_timecount, /* get_timecount */
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0, /* no poll_pps */
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0xffffff, /* counter_mask */
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0, /* frequency */
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"PIIX" /* name */
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};
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static int
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sysctl_machdep_piix_freq(SYSCTL_HANDLER_ARGS)
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{
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int error;
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u_int freq;
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if (piix_timecounter.tc_frequency == 0)
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return (EOPNOTSUPP);
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freq = piix_freq;
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error = sysctl_handle_int(oidp, &freq, sizeof(freq), req);
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if (error == 0 && req->newptr != NULL) {
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piix_freq = freq;
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piix_timecounter.tc_frequency = piix_freq;
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}
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return (error);
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}
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SYSCTL_PROC(_machdep, OID_AUTO, piix_freq, CTLTYPE_INT | CTLFLAG_RW,
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0, sizeof(u_int), sysctl_machdep_piix_freq, "I", "");
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static unsigned
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piix_get_timecount(struct timecounter *tc)
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{
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unsigned u1, u2, u3;
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u2 = inl(piix_timecounter_address);
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u3 = inl(piix_timecounter_address);
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do {
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u1 = u2;
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u2 = u3;
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u3 = inl(piix_timecounter_address);
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} while (u1 > u2 || u2 > u3);
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return (u2);
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}
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static int
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piix_probe(device_t dev)
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{
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u_int32_t d;
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if (devclass_get_device(devclass_find("acpi"), 0) != NULL)
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return (ENXIO);
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switch (pci_get_devid(dev)) {
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case 0x71138086:
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device_set_desc(dev, "PIIX Timecounter");
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break;
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default:
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return (ENXIO);
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}
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d = pci_read_config(dev, PCIR_COMMAND, 2);
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if (!(d & PCIM_CMD_PORTEN)) {
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device_printf(dev, "PIIX I/O space not mapped\n");
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return (ENXIO);
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}
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return (0);
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}
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static int
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piix_attach(device_t dev)
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{
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u_int32_t d;
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d = pci_read_config(dev, 0x40, 4);
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piix_timecounter_address = (d & 0xffc0) + 8;
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piix_timecounter.tc_frequency = piix_freq;
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tc_init(&piix_timecounter);
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return (0);
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}
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static device_method_t piix_methods[] = {
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/* Device interface */
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DEVMETHOD(device_probe, piix_probe),
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DEVMETHOD(device_attach, piix_attach),
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{ 0, 0 }
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};
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static driver_t piix_driver = {
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"piix",
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piix_methods,
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1,
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};
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static devclass_t piix_devclass;
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DRIVER_MODULE(piix, pci, piix_driver, piix_devclass, 0, 0);
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