[PATCH 2/3] ARM: sched_clock: support 64-bit counters

[Russell King - ARM Linux]

On Fri, Mar 22, 2013 at 07:58:39AM -0500, Rob Herring wrote:
> The ARM ARM also says the roll-over time must be greater than 40 years.
> So if you have fewer bits, then it needs to run at lower frequency. So I
> think we should be fine.

Well, we have a problem with 32-bit systems in about 19 years time when
32-bit Unix timestamps wrap.  Of course, by that time we'll all be
64-bit won't we. :)

Another issue here is whether it's likely that a system will have an
uptime of 40+ years.  Probably not.  The longest I can think of which
I have come across is the digital public address system on the London
Jubilee Line (Waterloo to Stratford section) which was specified to
have a life of 20 to 30 years... Hmm, I wonder of my Linux based system
activity logger is still in the Stratford PA racks. :)