[RFC 1/2] AT91: Support SAM9260 and SAM9G20-based boards in the same kernel image

[Russell King - ARM Linux]

On Tue, Jan 18, 2011 at 04:00:30PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> this idea is to do not have CONFIG_ARCH_AT91SAM9G20 anymore only 9260
> 
> and detect it
> 
> but the man issue is the CLOCK_TICK_RATE which is different between both of
> them except if we use a common one for those soc or the sam9/11 we could not
> put them in the same kernel

If you switch to clocksource/clockevents, then I think CLOCK_TICK_RATE
is irrelevant as time advances according to the interval measured by
the previous and current clocksource read, rather than 1/HZ intervals.

However, I'm never happy to say "just set CLOCK_TICK_RATE to some random
value that's a multiple of HZ" because I can't convince myself that these
don't have any effect when using clocksources.  The list of symbols which
depend on CLOCK_TICK_RATE are:

ACTHZ
LATCH
TICK_NSEC
TICK_USEC_TO_NSEC
LOW_RES_NSEC
MONOTONIC_RES_NSEC
NSEC_PER_JIFFY
KTIME_LOW_RES

and if you grep for those outside of arch/, you find them being used in
a fair amount of code under kernel/, as well as the odd driver here and
there.