[U-Boot-Users] PXA270 support

Wolfgang Denk wd at denx.de
Tue Mar 15 01:00:53 CET 2005

In message <71555548814716479478431542AA5F8A01B1B6D9 at dlee2k04.ent.ti.com> you wrote:
> 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

Yes, it is variable, and this is why you  can  configure  it  through

> 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
> something.

This is your interpretation.

Sorry, but it is not up to you to redefine the meaning of a  variable
at your liking.

> For ARM, it turns out to be convenient to assign the tick generator to
> be CFG_HZ value.  This saves on a little math.

Maybe. Feel free to use any other definition then, but please do  NOT
use CFG_HZ for this which serves a different purpose.

Also be aware that assinging arbitray values may cause lots of problems
like integer overflows:

Configuring for dbau1x00 board...
net.c: In function `NetStartAgain':
net.c:565: warning: integer overflow in expression
nfs.c: In function `NfsHandler':
nfs.c:671: warning: integer overflow in expression
nfs.c: In function `NfsStart':
nfs.c:760: warning: integer overflow in expression

This comes from simple  statements  like  setting  up  a  10  seconds
timeout using "10 * CFG_HZ".


> 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.

The kernel can do whatever it likes.

Nevertheless, please do not  continue  to  misuse  CFG_HZ  for  other
purposes  than  it  was intended for. I will reject any patches which
continue to contain such code (sorry it took me  that  long  to  even
become aware of such misuse).

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
In C we had to code our own bugs, in C++ we can inherit them.

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