[U-Boot-Users] TEXT_BASE and hardware configuration word on MPC8248

[U-Boot-Users] TEXT_BASE and hardware configuration word on MPC8248

[Laurent Pinchart]

Hi everybody,

I've been able to flash an Embedded Planet EP8248 board with u-boot 1.1.4 with 
success, and I'm now trying to run it on a custom MPC8248 based board.

The custom board, unlike the EP8248 which provides the hardware reset 
configuration word through the on board FPGA, stores the HRCW in flash 
memory.

The board has a single 16-bit 128Mbit flash chip, which is mapped at 
0xFF000000.

I'm a bit puzzled by the way the u-boot image is relocated at link time. 
TEXT_BASE is defined as 0xFFF00000, as the board boots from high memory. The 
_start symbol is located at 0xFFF00100, which looks fine to me. However, the 
HRCW is stored at 0xFFF00000, while it should in my opinion be at the 
beginning of the flash at 0xFF000000.

Is there something I don't understand in the MPC8248 boot process ?

Thanks in advance for all the help you can provide.

Best regards,

Laurent Pinchart

[U-Boot-Users] TEXT_BASE and hardware configuration word on MPC8248

[Andre Schwarz]

Hello Laurent,

the CPU has two starting points called "low boot" and "high boot".
It's either the first or the last MB of the address space, i.e. 0x0 or 
0xFFF00000. It is just a matter of mapping the flash into local memory. In 
either case, the reset exception vector is located at offset 0x100, thus 
results in 0x00000100 or 0xFFF00100.

The reset vector is NOT RELATED to the flash base address.


regards,
Andr?

On Thursday 04 May 2006 13:38, Laurent Pinchart wrote:
> Hi everybody,
>
> I've been able to flash an Embedded Planet EP8248 board with u-boot 1.1.4
> with success, and I'm now trying to run it on a custom MPC8248 based board.
>
> The custom board, unlike the EP8248 which provides the hardware reset
> configuration word through the on board FPGA, stores the HRCW in flash
> memory.
>
> The board has a single 16-bit 128Mbit flash chip, which is mapped at
> 0xFF000000.
>
> I'm a bit puzzled by the way the u-boot image is relocated at link time.
> TEXT_BASE is defined as 0xFFF00000, as the board boots from high memory.
> The _start symbol is located at 0xFFF00100, which looks fine to me.
> However, the HRCW is stored at 0xFFF00000, while it should in my opinion be
> at the beginning of the flash at 0xFF000000.
>
> Is there something I don't understand in the MPC8248 boot process ?
>
> Thanks in advance for all the help you can provide.
>
> Best regards,
>
> Laurent Pinchart
>
>
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