[U-Boot] Problems booting without BDI

[Ben Warren <biggerbadderben@gmail.com>]

David Hawkins wrote:
> Hi Alemao,
>
>   
>> I made a port of u-boot for my board, with MPC8343.
>>
>> The problem is that when i run u-boot with the BDI2000 (using "reset run"
>> command), u-boot loads normally, but when i take off the BDI nothing
>> appears on serial.
>>
>> BDI is setting the reset configuration word, and is the same word found
>> in u-boot image. I commented the line wich BDI sets the reset word, and
>> tried to read it from the BDI, its seems ok _BUT_, nothing appears on serial.
>>
>> Any ideas about what could be happening?
>>     
>
> Perhaps your processor is not being driven with the correct
> pin strapping values to cause it to read configuration reset
> words from Flash.
>
> Check the schematic connections for the configuration reset
> words source pins (they're LGPL pins that do dual duty during
> boot).
>
> The assignments for the 8349 are:
>
> CFG_RS[0:2] = LGPL[0, 1, 3]
> CFG_CLKIN_DIV = LGPL[5]
>
> Look in the reference manual for your processor. Now that you
> know what you are looking for, it should be easy to locate.
>
> The CFG_xx pins need to be driven at reset, they're captured
> by the processing on the rising edge of PRST#. You may find
> that the design has a tri-state buffer being controlled by
> the HRST# pin; when HRST# is low, the signals are driven,
> when high, they're disabled and used as GPIO/LBC signals.
>
> These comments are based on my experience with the 8349,
> but the 8343 should be similar.
>
> Cheers,
> Dave
>
>
>   
To somewhat re-phrase what Dave mentioned, one common issue is that at 
boot time, the four least-significant local bus address bits are driven 
by different signals than the standard local bus address bits (sorry, 
don't have the documentation here so don't know the exact names).  
Without this you can't red the RCW words from NOR flash.  Compare your 
schematic to the one for the MPC8349EMDS to make sure you got this right.

regards,
Ben