The RTC offset correction documentation is not very clear about the
exact relationship between "offset" and the effect it has on the RTC.
Supplement the documentation with an equation giving the relationship.
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

If there is any non expired timer in the queue, the RTC alarm is never set.
This is an issue when adding a timer that expires before the next non
expired timer.

Ensure the RTC alarm is set in that case.

Fixes: 2b2f5ff0 ("rtc: interface: ignore expired timers when enqueuing new timers")
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

In function __rtc_read_alarm() its possible for an alarm time-stamp to
be invalid even after replacing missing components with current
time-stamp. The condition 'alarm->time.tm_year < 70' will trigger this
case and will cause the call to 'rtc_tm_to_time64(&alarm->time)'
return a negative value for variable t_alm.

While handling alarm rollover this negative t_alm (assumed to seconds
offset from '1970-01-01 00:00:00') is converted back to rtc_time via
rtc_time64_to_tm() which results in this error log with seemingly
garbage values:

"rtc rtc0: invalid alarm value: -2-1--1041528741
2005511117:71582844:32"

This error was generated when the rtc driver (rtc-opal in this case)
returned an alarm time-stamp of '00-00-00 00:00:00' to indicate that
the alarm is disabled. Though I have submitted a separate fix for the
rtc-opal driver, this issue may potentially impact other
existing/future rtc drivers.

To fix this issue the patch validates the alarm time-stamp just after
filling up the missing datetime components and if rtc_valid_tm() still
reports it to be invalid then bails out of the function without
handling the rollover.
Reported-by: NSteve Best <sbest@redhat.com>
Signed-off-by: NVaibhav Jain <vaibhav@linux.vnet.ibm.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

ktime_set(S,N) was required for the timespec storage type and is still
useful for situations where a Seconds and Nanoseconds part of a time value
needs to be converted. For anything where the Seconds argument is 0, this
is pointless and can be replaced with a simple assignment.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>

ktime is a union because the initial implementation stored the time in
scalar nanoseconds on 64 bit machine and in a endianess optimized timespec
variant for 32bit machines. The Y2038 cleanup removed the timespec variant
and switched everything to scalar nanoseconds. The union remained, but
become completely pointless.

Get rid of the union and just keep ktime_t as simple typedef of type s64.

The conversion was done with coccinelle and some manual mopping up.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>

Signed-off-by: NUwe Kleine-König <uwe@kleine-koenig.org>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

This patch fixes a RTC wakealarm issue, namely, the event fires during
hibernate and is not cleared from the list, causing hwclock to block.

The current enqueuing does not trigger an alarm if any expired timers
already exist on the timerqueue. This can occur when a RTC wake alarm
is used to wake a machine out of hibernate and the resumed state has
old expired timers that have not been removed from the timer queue.
This fix skips over any expired timers and triggers an alarm if there
are no pending timers on the timerqueue. Note that the skipped expired
timer will get reaped later on, so there is no need to clean it up
immediately.

The issue can be reproduced by putting a machine into hibernate and
waking it with the RTC wakealarm.  Running the example RTC test program
from tools/testing/selftests/timers/rtctest.c after the hibernate will
block indefinitely.  With the fix, it no longer blocks after the
hibernate resume.

BugLink: http://bugs.launchpad.net/bugs/1333569Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

rtc drivers are supposed to set values they don't support to -1. To
simplify this for drivers and also make it harder for them to get it
wrong initialize the values to -1.
Signed-off-by: NUwe Kleine-König <uwe@kleine-koenig.org>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

A number of rtc devices, such as the NXP pcf2123 include a facility
to adjust the clock in order to compensate for temperature or a
crystal, capacitor, etc, that results in the rtc clock not running
at exactly 32.768 kHz.

Data sheets I have seen refer to this as a clock offset, and measure it
in parts per million, however they often reference ppm to 2 digits of
precision, which makes integer ppm less than ideal.

We use parts per billion, which more than covers the precision needed
and works nicely within 32 bits
Signed-off-by: NJoshua Clayton <stillcompiling@gmail.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag and there
is no need to do that again from its callers. Drop it.

gemini driver was using likely() for a failure case while the rtc driver
is getting registered. That looks wrong and it should really be
unlikely. But because we are killing all the unlikely() flags, lets kill
that too.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Acked-by: NHans Ulli Kroll <ulli.kroll@googlemail.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

Now rtc_set_mmss() has no users, just remove it.

We still have rtc_set_time() doing similar things.
Signed-off-by: NXunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

The rtc_timer_cancel() always returns 0 and cannot fail (calls only
other void-returning functions).
Signed-off-by: NKrzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

__rtc_read_time logs should be debug logs instead of error logs.

For example, when the RTC clock is not set, it's not really useful
to print a kernel error log every time someone tries to read the clock:

	~ # hwclock -r
	[  604.508263] rtc rtc0: read_time: fail to read
	hwclock: RTC_RD_TIME: Invalid argument

If there's a real error, it's likely that lower level or higher level
code will tell it anyway. Make these logs debug logs, and also print
the error code for the read failure.
Signed-off-by: NAaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently the rtc_class_op's set_mmss() function takes a 32-bit
second value (on 32-bit systems), which is problematic for dates
past y2038.

This patch provides a safe version named set_mmss64() using
y2038 safe time64_t.

After this patch, set_mmss() is deprecated and all its users
will be fixed to use set_mmss64(), it can be removed when having
no users.
Signed-off-by: NXunlei Pang <pang.xunlei@linaro.org>
[jstultz: Add whitespace fix for checkpatch]
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
Acked-by: NAlessandro Zummo <a.zummo@towertech.it>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1427945681-29972-8-git-send-email-john.stultz@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Currently, interface.c uses y2038 problematic rtc_tm_to_time()
and rtc_time_to_tm(). So replace them with their corresponding
y2038-safe versions: rtc_tm_to_time64() and rtc_time64_to_tm().

Cc: pang.xunlei <pang.xunlei@linaro.org>
Cc: Arnd Bergmann <arnd.bergmann@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: NXunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

rtc_timer_do_work() only judges -ETIME failure of__rtc_set_alarm(), but
doesn't handle other failures like -EIO, -EBUSY, etc.

If there is a failure other than -ETIME, the next rtc_timer will stay in
the timerqueue.  Then later rtc_timers will be enqueued directly because
they have a later expires time, so the alarm irq will never be programmed.

When such failures happen, this patch will retry __rtc_set_alarm(), if
still can't program the alarm time, it will remove current rtc_timer from
timerqueue and fetch next one, thus preventing it from affecting other rtc
timers.
Signed-off-by: NXunlei Pang <pang.xunlei@linaro.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Arnd Bergmann <arnd.bergmann@linaro.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Some rtc devices always return '0' when rtc_class_ops.read_time is
called.  So if rtc_time isn't verified in callback, rtc interface cannot
know whether rtc_time is valid.

Check rtc_time by using 'rtc_valid_tm' in '__rtc_read_time'.  And add
the message for debugging.
Signed-off-by: NHyogi Gim <hyogi.gim@lge.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In __rtc_set_alarm(), the error after __rtc_read_time() is not checked.
If rtc device fail to read time, we cannot guarantee the following
process.

Add the verification code for returned __rtc_read_time() error.
Signed-off-by: NHyogi Gim <hyogi.gim@lge.com>
Acked-by: NAlessandro Zummo <a.zummo@towertech.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In __rtc_read_alarm(), if the alarm time retrieved by
rtc_read_alarm_internal() from the device contains invalid values (e.g.
month=2,mday=31) and the year not set (=-1), the initialization will
loop infinitely because the year-fixing loop expects the time being
invalid due to leap year.

Fix reduces the loop to the leap years and adds final validity check.
Signed-off-by: NAles Novak <alnovak@suse.cz>
Acked-by: NAlessandro Zummo <a.zummo@towertech.it>
Reported-by: NJiri Bohac <jbohac@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This small addition to the core simplifies code in the drivers and makes
them more robust when handling shared IRQs.
Signed-off-by: NAlessandro Zummo <a.zummo@towertech.it>
Cc: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Current implementation of RTC interface allows for system suspend to
occur in the following cases:
(a) if a timer is set in the past and rtc_timer_do_work() is scheduled
to handle it, and
(b) if rtc_timer_do_work() is called to handle expired timers whose
handlers implement a preemption point.

A pending suspend request may be honoured in the above cases causing
timer handling to be delayed until after the next resume. This is
undesirable since timer handlers may have time-critical code to execute.

This patch makes sure that the system stays awake until all expired
timers are handled.

Note that all calls to pm_stay_awake() are eventually paired with
the single pm_relax() call in rtc_timer_do_work(), which is launched
using schedule_work().

Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Arve Hjonnevag <arve@android.com>
Cc: Todd Poynor <toddpoynor@google.com>
Signed-off-by: NZoran Markovic <zoran.markovic@linaro.org>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

If rtc->irq_task is non-NULL and task is NULL, they always
rtc_irq_set_freq(), whenever err is set to -EBUSY it will then immediately
be set to -EACCES, misleading the caller as to the underlying problem.
Signed-off-by: NChris Brand <chris.brand@broadcom.com>
Acked-by: NAlessandro Zummo <a.zummo@towertech.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fixes the following types of errors:
  ERROR: "foo* bar" should be "foo *bar"
  ERROR: else should follow close brace '}'
  WARNING: braces {} are not necessary for single statement blocks
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Cc: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

All in-kernel users of class_find_device() don't really need mutable
data for match callback.

In two places (kernel/power/suspend_test.c, drivers/scsi/osd/osd_uld.c)
this patch changes match callbacks to use const search data.

The const is propagated to rtc_class_open() and power_supply_get_by_name()
parameters.

Note that there's a dev reference leak in suspend_test.c that's not
touched in this patch.
Signed-off-by: NMichał Mirosław <mirq-linux@rere.qmqm.pl>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

If an RTC alarm fires just as suspend is happening, it is possible for
suspend to complete and the alarm to be missed.

To avoid the race, we must register the event with the PM core.

As the event is made visible to userspace through a thread which is
only scheduled by the interrupt, we need a pm_stay_awake/pm_relax
pair preventing suspend from the interrupt until the thread completes
its work.

This makes the pm_wakeup_event() call in cmos_interrupt unnecessary as
it provides suspend protection for all RTCs that use rtc_update_irq.
Signed-off-by: NNeilBrown <neilb@suse.de>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Richard Weinberger noticed that on some RTC hardware that
doesn't support UIE mode, due to coarse granular alarms
(like 1minute resolution), the current virtualized RTC
support doesn't properly error out when UIE is enabled.

Instead the current code queues an alarm for the next second,
but it won't fire until up to a miniute later.

This patch provides a generic way to flag this sort of hardware
and fixes the issue on the mpc5121 where Richard noticed the
problem.

CC: stable@vger.kernel.org
Reported-by: NRichard Weinberger <richard@nod.at>
Tested-by: NRichard Weinberger <richard@nod.at>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

Currently, the RTC code does not disable the alarm in the hardware.

This means that after a sequence such as the one below (the files are in the
RTC sysfs), the box will boot up after 2 minutes even though we've
asked for the alarm to be turned off.

	# echo $((`cat since_epoch`)+120) > wakealarm
	# echo 0 > wakealarm
	# poweroff

Fix this by disabling the alarm when there are no timers to run.

The original version of this patch was reverted. This version
disables the irq directly instead of setting a disabled timer
in the future.

Cc: stable@kernel.org
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: NRabin Vincent <rabin.vincent@stericsson.com>
[Merged in the second revision from Rabin]
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

If the alarm time programming in the rtc is ever in the past, it won't fire,
and any other alarm will be queued after it so they won't fire either.

So any time that the alarm might be in the past, we need to trigger
the irq handler to ensure the old alarm is cleared and the timer queue
is fully in the future.

This is done whenever the RTC clock is set.

This is the second revision of this patch, which was earlier reverted.
This version avoids the initialization problem, which is handled by
a different patch.
Tested-by: NSander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: NNeilBrown <neilb@suse.de>
[Remove problematic initialization change, update commit log, also
catch set_mmss case -jstultz]
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

In some cases at boot up, the RTC alarm may be set in the past,
but still have the enabled flag on. This was causing problems,
because we would then enqueue the alarm into the timerqueue,
but it would never fire. This would clog up the timerqueue
and keep other alarms from working.

The fix is to check the alarm against the current rtc time at
boot and avoid enqueueing the alarm if it is in the past.
Reported-by: NNeilBrown <neilb@suse.de>
Tested-by: NNeilBrown <neilb@suse.de>
Tested-by: NSander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

Commit f44f7f96 ("RTC: Initialize kernel state from RTC") introduced a
potential infinite loop.  If an alarm time contains a wildcard month and
an invalid day (> 31), or a wildcard year and an invalid month (>= 12),
the loop searching for the next matching date will never terminate.  Treat
the invalid values as wildcards.

Fixes <http://bugs.debian.org/646429>, <http://bugs.debian.org/653331>
Reported-by: Nleo weppelman <leoweppelman@googlemail.com>
Reported-by: N"P. van Gaans" <mailme667@yahoo.co.uk>
Signed-off-by: NBen Hutchings <ben@decadent.org.uk>
Signed-off-by: NJonathan Nieder <jrnieder@gmail.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Marcelo Roberto Jimenez <mroberto@cpti.cetuc.puc-rio.br>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Acked-by: NAlessandro Zummo <a.zummo@towertech.it>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This reverts commit 93b2ec01.

The call to "schedule_work()" in rtc_initialize_alarm() happens too
early, and can cause oopses at bootup

Neil Brown explains why we do it:

  "If you set an alarm in the future, then shutdown and boot again after
   that time, then you will end up with a timer_queue node which is in
   the past.

   When this happens the queue gets stuck.  That entry-in-the-past won't
   get removed until and interrupt happens and an interrupt won't happen
   because the RTC only triggers an interrupt when the alarm is "now".

   So you'll find that e.g.  "hwclock" will always tell you that
   'select' timed out.

   So we force the interrupt work to happen at the start just in case."

and has a patch that convert it to do things in-process rather than with
the worker thread, but right now it's too late to play around with this,
so we just revert the patch that caused problems for now.
Reported-by: NSander Eikelenboom <linux@eikelenboom.it>
Requested-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Requested-by: NJohn Stultz <john.stultz@linaro.org>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This reverts commit c0afabd3.

It causes failures on Toshiba laptops - instead of disabling the alarm,
it actually seems to enable it on the affected laptops, resulting in
(for example) the laptop powering on automatically five minutes after
shutdown.

There's a patch for it that appears to work for at least some people,
but it's too late to play around with this, so revert for now and try
again in the next merge window.

See for example

	http://bugs.debian.org/652869

Reported-and-bisected-by: Andreas Friedrich <afrie@gmx.net> (Toshiba Tecra)
Reported-by: Antonio-M. Corbi Bellot <antonio.corbi@ua.es> (Toshiba Portege R500)
Reported-by: Marco Santos <marco.santos@waynext.com> (Toshiba Portege Z830)
Reported-by: Christophe Vu-Brugier <cvubrugier@yahoo.fr>  (Toshiba Portege R830)
Cc: Jonathan Nieder <jrnieder@gmail.com>
Requested-by: NJohn Stultz <john.stultz@linaro.org>
Cc: stable@kernel.org  # for the versions that applied this
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If the alarm time programming in the rtc is ever in the past, it won't fire,
and any other alarm will be queued after it so they won't fire either.

So any time that the alarm might be in the past, we need to trigger
the irq handler to ensure the old alarm is cleared and the timer queue
is fully in the future.

This can happen:
 - when we first initialise the alarm
 - when we set the time in the rtc.

so follow both of these by scheduling the timer work function.

CC: stable@kernel.org
Signed-off-by: NNeilBrown <neilb@suse.de>
[Also catch set_mmss case -jstultz]
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

Currently, the RTC code does not disable the alarm in the hardware.

This means that after a sequence such as the one below (the files are in the
RTC sysfs), the box will boot up after 2 minutes even though we've
asked for the alarm to be turned off.

	# echo $((`cat since_epoch`)+120) > wakealarm
	# echo 0 > wakealarm
	# poweroff

Fix this by disabling the alarm when there are no timers to run.

Cc: stable@kernel.org
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: NRabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

The module.h was implicitly everywhere, but when we clean
that up, the implicit users will compile fail; fix them up
in advance.
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

Thomas earlier submitted a fix to limit the RTC PIE freq, but
picked 5000Hz out of the air. Willy noticed that we should
instead use the 8192Hz max from the rtc man documentation.

Cc: Willy Tarreau <w@1wt.eu>
Cc: stable@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>

Ben reported a lockup related to rtc. The lockup happens due to:

CPU0                                        CPU1

rtc_irq_set_state()			    __run_hrtimer()
  spin_lock_irqsave(&rtc->irq_task_lock)    rtc_handle_legacy_irq();
					      spin_lock(&rtc->irq_task_lock);
  hrtimer_cancel()
    while (callback_running);

So the running callback never finishes as it's blocked on
rtc->irq_task_lock.

Use hrtimer_try_to_cancel() instead and drop rtc->irq_task_lock while
waiting for the callback.  Fix this for both rtc_irq_set_state() and
rtc_irq_set_freq().
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reported-by: NBen Greear <greearb@candelatech.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Due to the hrtimer self rearming mode a user can DoS the machine simply
because it's starved by hrtimer events.

The RTC hrtimer is self rearming.  We really need to limit the frequency
to something sensible.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ben Greear <greearb@candelatech.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The code checks the correctness of the parameters, but unconditionally
arms/disarms the hrtimer.

The result is that a random task might arm/disarm rtc timer and surprise
the real owner by either generating events or by stopping them.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ben Greear <greearb@candelatech.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The RTC pie hrtimer is self rearming. We really need to limit the
frequency to something sensible. Thus limit it to the 8192Hz max
value from the rtc man documentation

Cc: Willy Tarreau <w@1wt.eu>
Cc: stable@kernel.org
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
[jstultz: slightly reworked to use RTC_MAX_FREQ value]
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>