[U-Boot-Users] dynamic setting of CONFIG_SYS_CLK_FREQ

Wolfgang Denk wd at denx.de
Mon Apr 26 10:02:11 CEST 2004

In message <408CAD48.4020004 at intracom.gr> you wrote:
> IMHO the gd data are pretty much useless in a complicated environment.

Agreed. But that's not what they were meant for.

The gd data is intended to store the absolute  minimum  of  rwritable
date  which  is  really  unavoidable to be stored in global variables
until the RAM has been initialized and a standard  data  segment  and
stack are available.

> For example when you have multiple network interfaces you have no
> information which network interface was used to obtain the configuration,
> which was it's ethernet address etc.

This is something which can easily be done after relocation  to  RAM,
so there is no need to use gd for this purpose.

> For me the gd is usefull only for the simple case of most boards with
> one network interface, fixed clock etc.

No. This is NOT the intention.

> For anything more complicated is better to parse the environment variables.

In the end we will probably have something like bi_recs ...

> Why don't we just add the missing information to the environment variables?

Because you cannot access envrionment in  very  early  initialization
steps,  or you have to do it in a very slow way (like reading byte by
byte from serial EEPROM), which would horribly slow down boot.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
I have a theory that it's impossible to prove anything, but  I  can't
prove it.

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