clocksource: document some basic timekeeping concepts

This adds some documentation about clock sources, clock events,
the weak sched_clock() function and delay timers that answers
questions that repeatedly arise on the mailing lists.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nicolas Pitre <nico@fluxnic.net>
Cc: Colin Cross <ccross@google.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>

diff --git a/Documentation/timers/00-INDEX b/Documentation/timers/00-INDEX
index 6d042dc..ee212a2 100644 (file)
--- a/Documentation/timers/00-INDEX
+++ b/Documentation/timers/00-INDEX
@@ -12,6 +12,8 @@ Makefile
        - Build and link hpet_example
 NO_HZ.txt
        - Summary of the different methods for the scheduler clock-interrupts management.
+timekeeping.txt
+       - Clock sources, clock events, sched_clock() and delay timer notes
 timers-howto.txt
        - how to insert delays in the kernel the right (tm) way.
 timer_stats.txt

diff --cc Documentation/timers/timekeeping.txt
Simple merge