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