kernel/include/linux/clocksource.h, branch linux-2.6.39.y

clocksource: Make watchdog robust vs. interruption

2011-07-09T06:15:05Z

commit b5199515c25cca622495eb9c6a8a1d275e775088 upstream. The clocksource watchdog code is interruptible and it has been observed that this can trigger false positives which disable the TSC. The reason is that an interrupt storm or a long running interrupt handler between the read of the watchdog source and the read of the TSC brings the two far enough apart that the delta is larger than the unstable treshold. Move both reads into a short interrupt disabled region to avoid that. Reported-and-tested-by: Vernon Mauery Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

clocksource: Add __clocksource_updatefreq_hz/khz methods

2010-07-27T10:40:55Z

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

2010-07-27T10:40:54Z

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

2010-05-10T12:24:26Z

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

2010-02-05T13:54:10Z

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

2010-02-05T13:54:10Z

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

2009-12-09T03:28:09Z

* '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

2009-11-17T10:52:34Z

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

2009-11-13T19:46:24Z

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

2009-11-13T19:46:23Z

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>