Early boot problem with MPC8247 and Linux 2.6.26

[Chris Skepper]

On Tue, 26 Aug 2008, Scott Wood wrote:

> On Tue, Aug 26, 2008 at 01:00:05PM +0100, Chris Skepper wrote:
>
>> I'm triggering an LED which is connected to port A.  Are you saying that
>> wouldn't work once the caching is enabled?
>
> It's quite possible.  What other registers are in the same cache line as
> the LED, and are any of them non-memory-like?

There are some ethernet signals, a compact flash card detect, other LEDs 
and a push button also on port A.  Are those what you'd call 
non-memory-like?

> It's usually easiest to just trust that that part of the code works (in
> my experience, that's rarely where a hang actually occurs when bringing
> up a new board), and resume tracing after the MMU is on and you've
> inserted a caching-inhibited BAT entry.

Where can I find out how to do that?  Since I have this board working with 
the old ARCH=ppc, can I copy anything from there?

Also, where would be a good place in the code to resume tracing?

Thanks for your help so far.  I see now it's probably not the code for 
enabling the cache that's causing the problem, it just masks my attempts 
at tracing using the LED.

Cheers,

Chris.