From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 16 Jul 2014 21:05:12 +0000 (+0000)
Subject: clocksource: Move cycle_last validation to core code
X-Git-Tag: omap-for-v3.17/fixes-against-rc2~152^2~13
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=09ec54429c6d10f87d1f084de53ae2c1c3a81108;p=pandora-kernel.git

clocksource: Move cycle_last validation to core code

The only user of the cycle_last validation is the x86 TSC. In order to
provide NMI safe accessor functions for clock monotonic and
monotonic_raw we need to do that in the core.

We can't do the TSC specific

    if (now < cycle_last)
       	    now = cycle_last;

for the other wrapping around clocksources, but TSC has
CLOCKSOURCE_MASK(64) which actually does not mask out anything so if
now is less than cycle_last the subtraction will give a negative
result. So we can check for that in clocksource_delta() and return 0
for that case.

Implement and enable it for x86

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
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