MFC r338435:
Improve error messages from clock_if.m method failures.

Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

MFC r325233, r328956, r329170, r329172-r329173, r329224, r330403-r330407,
r330411-r330412, r330416, r330430-r330431, r330433, r330528-r330529,
r330767

r325233:
[i2c/clock] add support for EPSON RTC-8583

RTC-8583 is time-of-day clock used in some SOHO routers. This clock has
only 2 bits for year values, but thanks to user SRAM it's possible to save
year value and keep it up to date via driver code.

Tested on Planex_MZK-W300NAG (SoC is RT2880)

Submitted by: Hiroki Mori <yamori83@yahoo.co.jp>
Differential Revision: https://reviews.freebsd.org/D12833

r328956:
Use const pointers for input data not modified by clock utility functions.

r329170:
Replace the existing print_ct() private debugging function with a set of
three public functions to format and print the three major data structures
used by realtime clock drivers (clocktime, bcd_clocktime, and timespec).

r329172:
Add a set of convenience routines for RTC drivers to use for debug output,
and a debug.clock_show_io sysctl to control debugging output.

r329173:
Add a new sysctl, debug.clock_do_io, to allow manully triggering a one-shot
read or write of all registered realtime clocks. In the read case, the
values read are simply discarded. For writes, there's no alternative but
to actually write the current system time to the device.

r329224:
Fix bad indentation. Whitespace only, no functional changes.

Reported by: bde@

r330403:
Add calls to the new clock_dbgprint_xxx() functions.

r330404:
Add calls to the new clock_dbgprint_xxx() functions.

r330405:
Oops, fix a paste-o.

r330406:
Add calls to the new clock_dbgprint_xxx() functions.

r330407:
Add calls to the new clock_dbgprint_xxx() functions. Also, stop applying
a local .5 second adjustment to the time, since that is now done by the
code in subr_rtc.c.

r330411:
Convert to the new(ish) bcd_clocktime conversion functions, add calls to
the new debug output functions, and when setting the clock, propagate the
timespec nsecs to the 1/100ths register.

r330412:
Build iicbus/rtc8583 as a module.

r330416:
The year is stored in a single byte in sram, in binary format, as a count
of years since the century, so strip the century out when converting to or
from bcd_clocktime format (the conversion routines will infer century by
pivoting on 70).

r330430:
Switch to the new bcd_clocktime conversion routines, and add calls to the
new clock_dbgprint_xxx() functions.

r330431:
Switch to the new bcd_clocktime conversion routines, and add calls to the
new clock_dbgprint_xxx() functions.

r330433:
Switch to the new bcd_clocktime conversion routines, and add calls to the
new clock_dbgprint_xxx() functions.

r330528:
Fix a paste-o that broke the build. There is no softc pointer here, just
use the dev arg.

Reported by: Jonathan Looney <jonlooney@gmail.com>
Pointy hat: ian@

r330529:
Build the ds1672 driver as a module. Add a detach() to unregister the rtc.

r330767:
Convert atrtc the new style rtc debugging output. Remove the db show
command handler which provided much the same information. Removing the
possibility of accessing the hardware regs from the debugger context
paves the way for simplifying the locking code in the driver.

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

MFC r320901-r320902, r320996-r320997, r321002, r321048, r321400, r321743,
r321745

r320901:
Protect access to the AT realtime clock with its own mutex.

The mutex protecting access to the registered realtime clock should not be
overloaded to protect access to the atrtc hardware, which might not even be
the registered rtc. More importantly, the resettodr mutex needs to be
eliminated to remove locking/sleeping restrictions on clock drivers, and
that can't happen if MD code for amd64 depends on it. This change moves the
protection into what's really being protected: access to the atrtc date and
time registers.

This change also adds protection when the clock is accessed from
xentimer_settime(), which bypasses the resettodr locking.

Differential Revision: https://reviews.freebsd.org/D11483

r320902:
Support multiple realtime clocks, and remove locking/sleeping restrictions
on clock drivers.

This tracks multiple concurrent realtime clock drivers in a list sorted by
clock resolution. When system time changes (and periodically) the
clock_settime() methods of all registered clocks are invoked.

To initialize system time, each driver is tried in turn from best to worst
resolution, until one succesfully returns a valid time.

The code no longer holds a mutex while calling the clock_settime() and
clock_gettime() methods of the registered clocks. This allows clock drivers
to do whatever kind of locking or sleeping is necessary (this is especially
important for i2c clock chips since i2c drivers often need to sleep).

A new clock_register_flags() function allows the clock driver to pass
flags. The flags currently defined help support drivers that use their own
techniques to avoid roundoff errors (prevents the 4/5 rounding done by the
subr_rtc code). A driver which may need to wait for resources (such as bus
ownership) may pass a flag to indicate that it will obtain system time for
itself after waiting for resources; this is merely an optimization to avoid
the common code retrieving a timespec that will never get used.

Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D11484

r320996:
Allow setting debug.clocktime as a tunable. Print 64-bit time_t correctly
on 32-bit systems.

r320997:
Minor optimization: instead of converting between days and years using
loops that start in 1970, assume most conversions are going to be for recent
dates and use a precomputed number of days through the end of 2016.

r321002:
Revert r320997. There are reports of it getting the wrong results, so
clearly my testing was insuffficent, and it's best to just revert it
until I get it straightened out.

r321048:
Minor optimization: instead of converting between days and years using loops
that start in 1970, assume most conversions are going to be for recent dates
and use a precomputed number of days through the end of 2016.

This is a do-over of r320997, hopefully this time with 100% more workiness.

The first attempt had an off-by-one error, but instead of just adding
another mysterious +1 adjustment, this rearranges the relationship between
recent_base_year and recent_base_days so that the latter is the number of
days that occurred before the start of the associated year (instead of the
count thru the end of that year). This makes the recent_base stuff work
more like the original loop logic that didn't need any +1 adjustments.

r321400:
Add common code to support realtime clocks that store year without century.

Most realtime clocks store the year as 2 BCD digits. Some add a century bit
to extend the range another hundred years. Every clock driver has its own
code to determine the century and pass a full year value to clock_ct_to_ts().
Now clock drivers can just convert BCD to bin and store the result in the
clocktime struct and let the common code figure out the century. Clocks
with a century bit can just add 100 to year if the century bit is on.

r321743:
Add taskqueue_enqueue_timeout_sbt(), because sometimes you want more control
over the scheduling precision than 'ticks' can offer, and because sometimes
you're already working with sbintime_t units and it's dumb to convert them
to ticks just so they can get converted back to sbintime_t under the hood.

r321745:
Add clock_schedule(), a feature that allows realtime clock drivers to
request that their clock_settime() methods be called at a given offset
from top-of-second. This adds a timeout_task to the rtc_instance so that
each clock can be separately added to taskqueue_thread with the scheduling
it prefers, instead of looping through all the clocks at once with a
single task on taskqueue_thread. If a driver doesn't call clock_schedule()
the default is the old behavior: clock_settime() is queued immediately.

MFC r306089:
Make resettodr_lock accessible outside subr_rtc.c. Protect
CLOCK_GETTIME() with the lock.

MFC r303385:
Reduce the resettodr_lock scope to only CLOCK_SETTIME() call.

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

Do not use Giant to prevent parallel calls to CLOCK_SETTIME(). Use
private mtx in resettodr(), no implementation of CLOCK_SETTIME() is
allowed to sleep.

Reviewed by: imp, jhb
Sponsored by: The FreeBSD Foundation
Approved by: re (gjb)
X-Differential revision: https://reviews.freebsd.org/D6825

rtc: fix inverted resolution check

The current code in clock_register checks if the newly added clock has a
resolution value higher than the current one in order to make it the
default, which is wrong. Clocks with a lower resolution value should be
better than ones with a higher resolution value, in fact with the current
code FreeBSD is always selecting the worse clock.

Reviewed by: kib jhb jkim
Sponsored by: Citrix Systems R&D
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D6185

Core structure and functions to support a feed-forward clock within the kernel.
Implement ffcounter, a monotonically increasing cumulative counter on top of the
active timecounter. Provide low-level functions to read the ffcounter and
convert it to absolute time or a time interval in seconds using the current
ffclock estimates, which track the drift of the oscillator. Add a ring of
fftimehands to track passing of time on each kernel tick and pick up updates of
ffclock estimates.

Committed on behalf of Julien Ridoux and Darryl Veitch from the University of
Melbourne, Australia, as part of the FreeBSD Foundation funded "Feed-Forward
Clock Synchronization Algorithms" project.

For more information, see http://www.synclab.org/radclock/

Submitted by: Julien Ridoux (jridoux at unimelb edu au)

Add the half of time-of-day clock resolution when we adjust system time from
time-of-day clock or vice versa. For x86 systems, RTC resolution is one
second and we used to lose up to one second whenever we initialize system
time from RTC or write system time back to RTC. With this change, margin
of error per conversion is roughly between -0.5 and +0.5 second rather
than between -1 and 0 second. Note that it does not take care of errors
from getnanotime(9) (which is up to 1/hz second) or CLOCK_GETTIME() latency.
These are just too expensive to correct and it is not worthy of the cost.

Provide description for 'machdep.disable_rtc_set' sysctl. Clean up style(9)
nits. Remove a redundant return statement and an unnecessary variable.

Clean up MI inittodr(9) and kill noop code.

It was derived from i386 version long ago but never resync'ed again.
Originally, i386 version compared the current time from realtime clock
with time_second (which was just `time' in the old days). When this MI
version was written, it was wrongly compared against `base' AND never
used because of a bug (typo?) in the code. This check was killed
in i386 version when home-rolled calendaric calculation was removed.
Now, we just remove the code here as well to make the code simpler.

int foo(void) is the proper ANSI function definition when there's no
parameters. Use it for resettodr().

Now that all platforms use genclock, shuffle things around slightly
for better structure.

Much of this is related to <sys/clock.h>, which should really have
been called <sys/calendar.h>, but unless and until we need the name,
the repocopy can wait.

In general the kernel does not know about minutes, hours, days,
timezones, daylight savings time, leap-years and such. All that
is theoretically a matter for userland only.

Parts of kernel code does however care: badly designed filesystems
store timestamps in local time and RTC chips almost universally
track time in a YY-MM-DD HH:MM:SS format, and sometimes in local
timezone instead of UTC. For this we have <sys/clock.h>

<sys/time.h> on the other hand, deals with time_t, timeval, timespec
and so on. These know only seconds and fractions thereof.

Move inittodr() and resettodr() prototypes to <sys/time.h>.
Retain the names as it is one of the few surviving PDP/VAX references.

Move startrtclock() to <machine/clock.h> on relevant platforms, it
is a MD call between machdep.c/clock.c. Remove references to it
elsewhere.

Remove a lot of unnecessary <sys/clock.h> includes.

Move the machdep.disable_rtc_set sysctl to subr_rtc.c where it belongs.
XXX: should be kern.disable_rtc_set really, it's not MD.

Use utc_offset() where applicable, and hide the internals of it
as static variables.

Second part of a little cleanup in the calendar/timezone/RTC handling.

Split subr_clock.c in two parts (by repo-copy):
subr_clock.c contains generic RTC and calendaric stuff. etc.
subr_rtc.c contains the newbus'ified RTC interface.

Centralize the machdep.{adjkerntz,disable_rtc_set,wall_cmos_clock}
sysctls and associated variables into subr_clock.c. They are
not machine dependent and we have generic code that relies on being
present so they are not even optional.

Remove more straggling CPU_ macro references

/* -> /*- for copyright notices, minor format tweaks as necessary

Remove advertising clause from University of California Regent's license,
per letter dated July 22, 1999.

Approved by: core

Use __FBSDID().

Split the global timezone structure into two integer fields to
prevent the compiler from optimizing assignments into byte-copy
operations which might make access to the individual fields non-atomic.

Use the individual fields throughout, and don't bother locking them with
Giant: it is no longer needed.

Inspired by: tjr

Use the CPU_* OID constants instead of OID_AUTO for the clock-related
sysctls for compatability with old applications.

Add a generic implementation of inittodr() and resettodr(), as well as
a set of helper routines to deal with real-time clocks. The generic
functions access the clock diver using a kobj interface. This is intended
to reduce code reduplication and make it easy to support more than one
clock model on a single architecture.

This code is currently only used on sparc64, but it is planned to convert
the code of the other architectures to it later.