[U-Boot-Users] Re: Failure of 2 BAT schemes to enable D-cache

Jerry Van Baren gerald.vanbaren at smiths-aerospace.com
Fri May 12 14:26:15 CEST 2006

Wolfgang Denk wrote:
> In message <20060511201329.23866.qmail at web37105.mail.mud.yahoo.com> you wrote:
>> Please post comments and suggestions of how I can
>> initialized MMU for d-cache performance. I am  new
>> to this.
> We have been through this before, several times. Many times actually.
> I have explained it to you, and so did others.
> It is perfectly fine with me if you ignore my advice. But then please
> stop posting the same question again and again here.
> You will not receive any new answers.
> Again, and definitely for the last time:
> It makes no sense to try to enable the data cache on a MPC82xx system
> in U-Boot; the time you could save if you succeeded  is  marginal  to
> your application startup time.
> And in Linux the D-Cache is enabled, so no changes are needed.
> Best regards,
> Wolfgang Denk

Furthermore, manipulating processor control registers interactively with 
a debugger (e.g. attempting to enable dcache) is somewhere between 
nearly impossible and totally impossible.  Read and understand the 
processor manual on the sequences required for changing control 
registers and enabling/disabling cache.  You cannot guarantee that the 
sequences will be done properly because the debugger has LOTS of unknown 
code running to implement what to you "looks like" a simple register 
write command.

Signing off on this thread,

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