[uClinux-dev] coldfire issue, _fault routine called setting VBR

angelo angelo70 at gmail.com
Tue May 18 17:05:23 EDT 2010

Dear all,

you probably remember my previous posts, i am back, after resolved 
issues with my SDRAM.
Now the memory finally works fine, but i still cannot see uClinux kernel 
start correctly.

A brief of the scenario:

Custom board, with coldfire MCF5307, 16MBytes Micron SDRAM, 4MBytes SST 

In the first 18K of the flash memory "colilo" bootloader has been 
written correctly.
 From offset 0 to 0x400 of the flash memory the "colilo" vector table  
has been written.
All the vector table offsets, except for the first @0, points to a 
_fault routine (led blinks).
Then, from 0x400, start the "colilo" code.

At reset, the "colilo" bootloader test the SDRAM memory, than start up 
correctly giving the prompt.

Kernel 2.6 has been prepared with sdram start at 0x00000000, vector 
start at 0x00000000, kernel code start at 0x400.

I load now through colilo "load" command the kernel (linux.bin) at 0x400 
(SDRAM, flash is remapped at 0xffc00000 from colilo at reset).
Once i run the code from 0x400, after some instructions the $pc jump to 
the "colilo" "_fault" routine.

I inserted a loop in 
linux-2.6.x/arch/m68knommu/platform/coldfire/head.S, to find the exact 
point where the jump happen, as below:

    nop               /* filler */
    movew #0x2700, %sr         /* no interrupts */

     * Do any platform or board specific setup now. Most boards
     * don't need anything. Those exceptions are define this in
     * their board specific includes.

     * Create basic memory configuration. Set VBR accordingly,
     * and size memory.
    movel #CONFIG_VECTORBASE,%a7
_loop: jmp _loop
    movec   %a7,%VBR        /* set vectors addr */ *<<-- this line cause 
the jump to _fault*
    movel %a7,_ramvec

Now i know the SDRAM is working correctly, but i am still stucked here.
Any help is really appreciated.

Many Thanks,

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