linux-toradex.git/include/linux/clocksource.h, branch v2.6.31.2

clocksource: Save mult_orig in clocksource_disable()

2009-07-31T12:12:36+00:00

To fix the common case where ->enable() does not set up
mult, make sure mult_orig is saved in mult on disable.

Also add comments to explain why we do this.

Signed-off-by: Magnus Damm 
Cc: johnstul@us.ibm.com
Cc: lethal@linux-sh.org
Cc: akpm@linux-foundation.org
LKML-Reference: <20090618152432.10136.9932.sendpatchset@rx1.opensource.se>
Signed-off-by: Thomas Gleixner

clocksource: setup mult_orig in clocksource_enable()

2009-05-02T09:45:15+00:00

Setup clocksource mult_orig in clocksource_enable().

Clocksource drivers can save power by using keeping the
device clock disabled while the clocksource is unused.

In practice this means that the enable() and disable()
callbacks perform clk_enable() and clk_disable().

The enable() callback may also use clk_get_rate() to get
the clock rate from the clock framework. This information
can then be used to calculate the shift and mult variables.

Currently the mult_orig variable is setup from mult at
registration time only. This is conflicting with the above
case since the clock is disabled and the mult variable is
not yet calculated at the time of registration.

Moving the mult_orig setup code to clocksource_enable()
allows us to both handle the common case with no enable()
callback and the mult-changed-after-enable() case.

[ Impact: allow dynamic clock source usage ]

Signed-off-by: Magnus Damm 
LKML-Reference: <20090501054546.8193.10688.sendpatchset@rx1.opensource.se>
Signed-off-by: Thomas Gleixner

clocksource: add enable() and disable() callbacks

2009-04-21T20:41:47+00:00

Add enable() and disable() callbacks for clocksources.

This allows us to put unused clocksources in power save mode.  The
functions clocksource_enable() and clocksource_disable() wrap the
callbacks and are inserted in the timekeeping code to enable before use
and disable after switching to a new clocksource.

Signed-off-by: Magnus Damm 
Acked-by: John Stultz 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

clocksource: pass clocksource to read() callback

2009-04-21T20:41:47+00:00

Pass clocksource pointer to the read() callback for clocksources.  This
allows us to share the callback between multiple instances.

[hugh@veritas.com: fix powerpc build of clocksource pass clocksource mods]
[akpm@linux-foundation.org: cleanup]
Signed-off-by: Magnus Damm 
Acked-by: John Stultz 
Cc: Thomas Gleixner 
Signed-off-by: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

clocksource: allow usage independent of timekeeping.c

2009-02-16T06:43:31+00:00

So far struct clocksource acted as the interface between time/timekeeping.c
and hardware. This patch generalizes the concept so that a similar
interface can also be used in other contexts. For that it introduces
new structures and related functions *without* touching the existing
struct clocksource.

The reasons for adding these new structures to clocksource.[ch] are
* the APIs are clearly related
* struct clocksource could be cleaned up to use the new structs
* avoids proliferation of files with similar names (timesource.h?
  timecounter.h?)

As outlined in the discussion with John Stultz, this patch adds
* struct cyclecounter: stateless API to hardware which counts clock cycles
* struct timecounter: stateful utility code built on a cyclecounter which
  provides a nanosecond counter
* only the function to read the nanosecond counter; deltas are used internally
  and not exposed to users of timecounter

The code does no locking of the shared state. It must be called at least
as often as the cycle counter wraps around to detect these wrap arounds.
Both is the responsibility of the timecounter user.

Acked-by: John Stultz 
Signed-off-by: Patrick Ohly 
Signed-off-by: David S. Miller

clocksource: introduce CLOCK_MONOTONIC_RAW

2008-08-21T07:50:24+00:00

In talking with Josip Loncaric, and his work on clock synchronization (see
btime.sf.net), he mentioned that for really close synchronization, it is
useful to have access to "hardware time", that is a notion of time that is
not in any way adjusted by the clock slewing done to keep close time sync.

Part of the issue is if we are using the kernel's ntp adjusted
representation of time in order to measure how we should correct time, we
can run into what Paul McKenney aptly described as "Painting a road using
the lines we're painting as the guide".

I had been thinking of a similar problem, and was trying to come up with a
way to give users access to a purely hardware based time representation
that avoided users having to know the underlying frequency and mask values
needed to deal with the wide variety of possible underlying hardware
counters.

My solution is to introduce CLOCK_MONOTONIC_RAW.  This exposes a
nanosecond based time value, that increments starting at bootup and has no
frequency adjustments made to it what so ever.

The time is accessed from userspace via the posix_clock_gettime() syscall,
passing CLOCK_MONOTONIC_RAW as the clock_id.

Signed-off-by: John Stultz 
Signed-off-by: Roman Zippel 
Signed-off-by: Andrew Morton 
Signed-off-by: Ingo Molnar

clocksource: keep track of original clocksource frequency

2008-08-21T07:50:23+00:00

The clocksource frequency is represented by
clocksource->mult/2^(clocksource->shift).  Currently, when NTP makes
adjustments to the clock frequency, they are made directly to the mult
value.

This has the drawback that once changed, we cannot know what the orignal
mult value was, or how much adjustment has been applied.

This property causes problems in calculating proper ntp intervals when
switching back and forth between clocksources.

This patch separates the current mult value into a mult and mult_orig
pair.  The mult_orig value stays constant, while the ntp clocksource
adjustments are done only to the mult value.

This allows for correct ntp interval calculation and additionally lays the
groundwork for a new notion of time, what I'm calling the monotonic-raw
time, which is introduced in a following patch.

Signed-off-by: John Stultz 
Signed-off-by: Roman Zippel 
Signed-off-by: Andrew Morton 
Signed-off-by: Ingo Molnar

ntp: handle leap second via timer

2008-05-01T15:03:59+00:00

Remove the leap second handling from second_overflow(), which doesn't have to
check for it every second anymore.  With CONFIG_NO_HZ this also makes sure the
leap second is handled close to the full second.  Additionally this makes it
possible to abort a leap second properly by resetting the STA_INS/STA_DEL
status bits.

Signed-off-by: Roman Zippel 
Cc: john stultz 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kgdb: clocksource watchdog

2008-04-17T18:05:38+00:00

In order to not trip the clocksource watchdog, kgdb must touch the
clocksource watchdog on the return to normal system run state.

Signed-off-by: Jason Wessel 
Signed-off-by: Ingo Molnar

clocksource: add unregister function to disable unusable clocksources

2008-01-30T12:30:02+00:00

On x86 the PIT might become an unusable clocksource. Add an unregister
function to provide a possibilty to remove the PIT from the list of
available clock sources.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Ingo Molnar