linux-toradex.git/include/linux/clocksource.h, branch v2.6.38.5

clocksource: Add __clocksource_updatefreq_hz/khz methods

2010-07-27T10:40:55+00:00

To properly handle clocksources that change frequencies
at the clocksource->enable() point, this patch adds
a method that will update the clocksource's mult/shift and
max_idle_ns values.

Signed-off-by: John Stultz 
LKML-Reference: <1279068988-21864-12-git-send-email-johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner

timkeeping: Fix update_vsyscall to provide wall_to_monotonic offset

2010-07-27T10:40:54+00:00

update_vsyscall() did not provide the wall_to_monotoinc offset,
so arch specific implementations tend to reference wall_to_monotonic
directly. This limits future cleanups in the timekeeping core, so
this patch fixes the update_vsyscall interface to provide
wall_to_monotonic, allowing wall_to_monotonic to be made static
as planned in Documentation/feature-removal-schedule.txt

Signed-off-by: John Stultz 
Cc: Martin Schwidefsky 
Cc: Anton Blanchard 
Cc: Paul Mackerras 
Cc: Tony Luck 
LKML-Reference: <1279068988-21864-7-git-send-email-johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner

clocksource: Add clocksource_register_hz/khz interface

2010-05-10T12:24:26+00:00

How to pick good mult/shift pairs has always been difficult to
describe to folks writing clocksource drivers, since it requires
careful tradeoffs in adjustment accuracy vs overflow limits.

Now, with the clocks_calc_mult_shift function, its much
easier. However, not many clocksources have converted to using that
function, and there is still the issue of the max interval length
assumption being made by each clocksource driver independently.

So this patch simplifies the registration process by having
clocksources be registered with a hz/khz value and the registration
function taking care of setting mult/shift.

This should take most of the confusion out of writing a clocksource
driver.

Additionally it also keeps the shift size tradeoff (more accuracy vs
longer possible nohz times) centralized so the timekeeping core can
keep track of the assumptions being made.

[ tglx: Coding style and comments fixed ]

Signed-off-by: John Stultz 
LKML-Reference: <1273280858-30143-1-git-send-email-johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner

clocksource: add suspend callback

2010-02-05T13:54:10+00:00

Add a clocksource suspend callback.  This callback can be used by the
clocksource driver to shutdown and perform any kind of late suspend
activities even though the clocksource driver itself is a non-sysdev
driver.

One example where this is useful is to fix the sh_cmt.c platform driver
that today suspends using the platform bus and shuts down the clocksource
too early.

With this callback in place the sh_cmt driver will suspend using the
clocksource and clockevent hooks and leave the platform device pm
callbacks unused.

Signed-off-by: Magnus Damm 
Cc: Paul Mundt 
Cc: john stultz 
Signed-off-by: Andrew Morton 
Signed-off-by: Thomas Gleixner

clocksource: add argument to resume callback

2010-02-05T13:54:10+00:00

Pass the clocksource as an argument to the clocksource resume callback. 
Needed so we can point out which CMT channel the sh_cmt.c driver shall
resume.

Signed-off-by: Magnus Damm 
Cc: john stultz 
Cc: Paul Mundt 
Signed-off-by: Andrew Morton 
Signed-off-by: Thomas Gleixner

Merge branch 'timers-for-linus-urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2009-12-09T03:28:09+00:00

* 'timers-for-linus-urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  hrtimer: Fix /proc/timer_list regression
  itimers: Fix racy writes to cpu_itimer fields
  timekeeping: Fix clock_gettime vsyscall time warp

timekeeping: Fix clock_gettime vsyscall time warp

2009-11-17T10:52:34+00:00

Since commit 0a544198 "timekeeping: Move NTP adjusted clock multiplier
to struct timekeeper" the clock multiplier of vsyscall is updated with
the unmodified clock multiplier of the clock source and not with the
NTP adjusted multiplier of the timekeeper.

This causes user space observerable time warps:
new CLOCK-warp maximum: 120 nsecs,  00000025c337c537 -> 00000025c337c4bf

Add a new argument "mult" to update_vsyscall() and hand in the
timekeeping internal NTP adjusted multiplier.

Signed-off-by: Lin Ming 
Cc: "Zhang Yanmin" 
Cc: Martin Schwidefsky 
Cc: Benjamin Herrenschmidt 
Cc: Tony Luck 
LKML-Reference: <1258436990.17765.83.camel@minggr.sh.intel.com>
Signed-off-by: Thomas Gleixner

nohz: Prevent clocksource wrapping during idle

2009-11-13T19:46:24+00:00

The dynamic tick allows the kernel to sleep for periods longer than a
single tick, but it does not limit the sleep time currently. In the
worst case the kernel could sleep longer than the wrap around time of
the time keeping clock source which would result in losing track of
time.

Prevent this by limiting it to the safe maximum sleep time of the
current time keeping clock source. The value is calculated when the
clock source is registered.

[ tglx: simplified the code a bit and massaged the commit msg ]

Signed-off-by: Jon Hunter 
Cc: John Stultz 
LKML-Reference: <1250617512-23567-2-git-send-email-jon-hunter@ti.com>
Signed-off-by: Thomas Gleixner

clocksource: Provide a generic mult/shift factor calculation

2009-11-13T19:46:23+00:00

MIPS has two functions to calculcate the mult/shift factors for clock
sources and clock events at run time. ARM needs such functions as
well.

Implement a function which calculates the mult/shift factors based on
the frequencies to which and from which is converted. The function
also has a parameter to specify the minimum conversion range in
seconds. This range is guaranteed not to produce a 64bit overflow when
a value is multiplied with the calculated mult factor. The larger the
conversion range the less becomes the conversion accuracy.

Provide two inline wrappers which handle clock events and clock
sources. For clock events the "from" frequency is nano seconds per
second which corresponds to 1GHz and "to" is the device frequency. For
clock sources "from" is the device frequency and "to" is nano seconds
per second.

Signed-off-by: Thomas Gleixner 
Tested-by: Mikael Pettersson 
Acked-by: Ralf Baechle 
Acked-by: Linus Walleij 
Cc: John Stultz 
LKML-Reference: <20091111134229.766673305@linutronix.de>

clocksource: Resolve cpu hotplug dead lock with TSC unstable

2009-08-28T18:25:24+00:00

Martin Schwidefsky analyzed it:
To register a clocksource the clocksource_mutex is acquired and if
necessary timekeeping_notify is called to install the clocksource as
the timekeeper clock. timekeeping_notify uses stop_machine which needs
to take cpu_add_remove_lock mutex.
Starting a new cpu is done with the cpu_add_remove_lock mutex held.
native_cpu_up checks the tsc of the new cpu and if the tsc is no good
clocksource_change_rating is called. Which needs the clocksource_mutex
and the deadlock is complete.

The solution is to replace the TSC via the clocksource watchdog
mechanism. Mark the TSC as unstable and schedule the watchdog work so
it gets removed in the watchdog thread context.

Signed-off-by: Thomas Gleixner 
LKML-Reference: 
Cc: Martin Schwidefsky 
Cc: John Stultz