[ECOS] Regarding eCos startup

[ECOS] Regarding eCos startup

[Dileep Kumar]

Hi,
I am trying to port eCos on MPC8555 processor . MPC8260 is
the baseline  I considered .

In MPC8555E processor when a reset occurs , control will go to
location FFFF_FFFC. This particular location always contain a
branch instruction to boot page.

In MPC8260 ecos2.0b1 code control will go to the point
"_exception_reset "  and the startup file is "vectors.S" .
( As specified in the linker script file " powerpc.ld ")
This  "  _exception_reset " comes under  " .vectors "  section

Well now , my problem is , it is not possible to load  " .vectors " section
at address starting from FFFF_FFFC, because this section is
bigger to hold at addresses FFF_FFFC, FFFF_FFFD,FFFF_FFFE and
FFFF_FFFF.

In Uboot code for MPC8555E , there is a separated file
" resetvec.S " ,this contain a single  branch  instruction to _start( which is
in the file start.S ) . This branch insrtuction is under the section
 " .resetvec " . This section can be loaded at FFFF_FFFC , because
it contain only one instruction .

One silution is to use the way what Uboot had done, but we have to change
linker script file (powerpc.ld ). This is not possible ,because it is
under  " arch " directory .

Is there any other solution to come out of this ?

Thanks
Dileep Kumar

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[ECOS] Re: Regarding eCos startup

[Wolfgang Denk]

In message <ed9edd1a0803200000h65639621pb4b4591336dcbbca@mail.gmail.com> you wrote:
>
> I am trying to port eCos on MPC8555 processor . MPC8260 is
> the baseline  I considered .

I think you are aware that there are a couple of significant
differences between PQII and PQIII systems...

> One silution is to use the way what Uboot had done, but we have to change
> linker script file (powerpc.ld ). This is not possible ,because it is
> under  " arch " directory .

It would be unrealistic to expect that such  different  architectures
could use the same memory layout and linker script. Consider creating
a  new  linker script for the new architecture. Power porcessors come
in a wide variety - expect that you  will  need  yet  another  linker
script when you port to the first 64bit system, etc.

Best regards,

Wolfgang Denk

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