[U-Boot-Users] PXA270 support
r-woodruff2 at ti.com
Tue Mar 15 00:44:58 CET 2005
> Mind the term "ticks" here. This is the "system tick", but not any of
> the clocks applied to any of the CPU pins.
> > second's value. I know I set up my timer with the CFG_HZ value in
> > to gauge udelays.
> CFG_HZ is the number of "clock ticks" per second; it has exactly the
> same meaning as the HZ variable in the Linux kernel.
> Like in current Linux kernels, U-Boot normally uses a 1 millisec
> system tick, thus CFG_HZ should be 1000.
Ok. The kernel's HZ value is variable on many architectures, so by the
same token I would say u-boots could be also. It should never be
assumed that CFG_HZ is 1000. Perhaps by convention it's a good rate for
the few PPC systems which actually use the clock interrupt to do
For ARM, it turns out to be convenient to assign the tick generator to
be CFG_HZ value. This saves on a little math.
I can see where it might be better to assign it to match the rate your
target kernel would use, but it is probably not necessary as the kernel
should re-init it anyway.
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