MFC 264019, 264041, 264048, 264049, 264050, 264051

  Add support for event timers whose clock frequency can change while running.

  Apparently all ARM configs build kern_et.c, but only a few of them also
  build kern_clocksource.c, un-break the build by not referencing functions in
  kern_clocksource if NO_EVENTTIMERS is defined.

  Add variable-frequency support to the arm mpcore eventtimer driver.

  mpcore_timer: Disable the timer and clear any pending bit, then setup the
  new counter register values, then restart the timer.  Also re-nest the parens
  properly for casting the result of converting time and frequency to a count.

1 files changed, 18 insertions, 1 deletions

diff --git a/share/man/man9/eventtimers.9 b/share/man/man9/eventtimers.9
index b43bc49..0c28d76 100644
--- a/share/man/man9/eventtimers.9
+++ b/share/man/man9/eventtimers.9
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd February 25, 2013
+.Dd April 2, 2014
 .Dt EVENTTIMERS 9
 .Os
 .Sh NAME
@@ -68,6 +68,8 @@ struct eventtimer {
 .Fn et_register "struct eventtimer *et"
 .Ft int
 .Fn et_deregister "struct eventtimer *et"
+.Ft void
+.Fn et_change_frequency "struct eventtimer *et" "uint64_t newfreq"
 .Fn ET_LOCK
 .Fn ET_UNLOCK
 .Ft struct eventtimer *
@@ -176,6 +178,21 @@ methods control timers associated with the current CPU.
 .Pp
 Driver may deregister its functionality by calling
 .Fn et_deregister .
+.Pp
+If the frequency of the clock hardware can change while it is 
+running (for example, during power-saving modes), the driver must call
+.Fn et_change_frequency
+on each change.
+If the given event timer is the active timer,
+.Fn et_change_frequency
+stops the timer on all CPUs, updates 
+.Va et->frequency ,
+then restarts the timer on all CPUs so that all
+current events are rescheduled using the new frequency.
+If the given timer is not currently active,
+.Fn et_change_frequency
+simply updates
+.Va et->frequency .
 .Sh CONSUMER API
 .Fn et_find
 allows consumer to find available event timer, optionally matching specific