[U-Boot-Users] dynamic setting of CONFIG_SYS_CLK_FREQ

Pantelis Antoniou
2004-04-26T08:16:37Z

Wolfgang Denk wrote:

>In message <408CAD48.4020004@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.
>
>
Correct.

But I'm not talking about the early initialization.

I'm talking about how the loaded image/kernel gets access to the
information.

At that point the variables are placed in RAM, and can contain
every info that is present in the gd structure.

U-boot can continue to use the gd structure, but the application
can access all it's configuration from the environment variables.

For example we can fill a environment variable with the system
clock value at the later stages of initialization.

>Best regards,
>
>Wolfgang Denk
>
>
Regards

Pantelis