Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Despite several examples in the kernel, the third argument of
sysctl_handle_int is not sizeof the int type you want to export.
The type must always be an int or an unsigned int.

Remove the instances where a sizeof(variable) is passed to stop
people accidently cut and pasting these examples.

In a few places this was sysctl_handle_int was being used on 64 bit
types, which would truncate the value to be exported. In these
cases use sysctl_handle_quad to export them and change the format
to Q so that sysctl(1) can still print them.

Add missing #include <sys/module.h>

- Fail to probe if acpi0 probed ok as this driver basically tries to probe
the ACPI timer and we shouldn't do that if ACPI is already around to do
that for us.
- Set a description and tweak the order of checks in the probe function
to more closely match other PCI drivers.

This should probably be moved to sys/dev/piix/piix.c at some point and
turned on for all i386 kernels rather than just SMP ones.

Whitespace.

Add comments to the members of the timecounter struct similar to other
timecounters.

Fix copyright comment & FBSDID style nits.

Requested by: bde

- Update location of PCI headers.
- Use macros for PCI config registers instead of magic numbers.
- Small whitespace nits.

Use __FBSDID().

Initialize the PIIX timecounter in piix_attach(), which is called only
once, instead of doing it in piix_probe(), which is called every time
the PCI bus is rescanned.

Remove a commented out #include "opt_pci.h", it doesn't
exist anymore.

Don't export timecounter structures under debug. with sysctl, they
contain no truly interesting data anymore.

Remove the tc_update() function. Any frequency change to the
timecounter will be used starting at the next second, which is
good enough for sysctl purposes. If better adjustment is needed
the NTP PLL should be used.

Remove the NCPU, NAPIC, NBUS, NINTR config options. Make NAPIC,
NBUS, NINTR dynamic and set NCPU to a maximum of 16 under SMP.

Reviewed by: peter

Previous commit changing SYSCTL_HANDLER_ARGS violated KNF.

Pointed out by: bde

Style police catches up with rev 1.26 of src/sys/sys/sysctl.h:

Sanitize SYSCTL_HANDLER_ARGS so that simplistic tools can grog our
sources:

-sysctl_vm_zone SYSCTL_HANDLER_ARGS
+sysctl_vm_zone (SYSCTL_HANDLER_ARGS)

Isolate the Timecounter internals in their own two files.

Make the public interface more systematically named.

Remove the alternate method, it doesn't do any good, only ruins performance.

Add counters to profile the usage of the 8 access functions.

Apply the beer-ware to my code.

The weird +/- counts are caused by two repocopies behind the scenes:
kern/kern_clock.c -> kern/kern_tc.c
sys/time.h -> sys/timetc.h
(thanks peter!)

How hard can it be to implement a 24bit counter in hardware ?

Make sure we read a likely value from the PIIX timecounter.

This should fix a large fraction of the "calcru: negative time"
warnings produced by SMP machines.

Another hole in one by: bde
Didn't belive Bruce: phk

Zap unneeded #includes

Submitted by: phk

Make the frequency tuneable via a sysctl.

Reviewed by: phk

On PIIX4 based SMP systems use the PMTMR register for timecounting.

It is about 2.5 microseconds or roughly 3 times faster to use this
"PIIX" timecounter than the "i8254" timecounter. Resolution is
also 3 times better.

The code cheats and don't register the PCI device, because other pieces
of code want to use it too.

Originally spotted by: msmith