MPC850 and GDB help

MPC850 and GDB help

[Ryan Wilkins]

Hello..  I'm very new to embedded systems but want to learn a bit more 
by using existing hardware.  In this case, the existing hardware is a 
DirectvDSL ADSL modem based on the MPC850 processor.  I've located the 
BDM port and built a MPCBDM version 2 interface to communicate with the 
MPC850.  The interface works just fine.

What I want to do now is to load the u-boot bootloader onto the board.  
What I'm trying to accomplish now is to load the u-boot code into ram 
and run it.  I don't have my flash definitions right in MPCBDM yet, 
otherwise I'd try to flash it.  I realize that this is not going to be 
an easy task, but what better way to learn than to dive right in.  So.. 
  I'm stumped.  Can anyone provide just a little bit of idea of where to 
go from here?  Perhaps a tutorial URL, or some past experience in 
working with the 850?

The board has a single 4 Mbyte flash chip (Intel DA28F320J5) and 16 
Mbyte RAM.

Thanks,
Ryan Wilkins

Re: MPC850 and GDB help

[Frank]

You probably want to post this to the u-boot users mailing
lists. Compiling and linking u-boot to run out of ram is not a
straight forward task. I've done it on more then one board, but
it is not easy if you're a u-boot novice.
Search the list for "running out of ram" or something like that
and you'll see what I mean.:-)


--- Ryan Wilkins <ryan@elevated-networks.com> wrote:

> Hello..  I'm very new to embedded systems but want to learn a
> bit more 
> by using existing hardware.  In this case, the existing
> hardware is a 
> DirectvDSL ADSL modem based on the MPC850 processor.  I've
> located the 
> BDM port and built a MPCBDM version 2 interface to communicate
> with the 
> MPC850.  The interface works just fine.
> 
> What I want to do now is to load the u-boot bootloader onto
> the board.  
> What I'm trying to accomplish now is to load the u-boot code
> into ram 
> and run it.  I don't have my flash definitions right in MPCBDM
> yet, 
> otherwise I'd try to flash it.  I realize that this is not
> going to be 
> an easy task, but what better way to learn than to dive right
> in.  So.. 
>   I'm stumped.  Can anyone provide just a little bit of idea
> of where to 
> go from here?  Perhaps a tutorial URL, or some past experience
> in 
> working with the 850?
> 
> The board has a single 4 Mbyte flash chip (Intel DA28F320J5)
> and 16 
> Mbyte RAM.
> 
> Thanks,
> Ryan Wilkins
> 
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
> 



		
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Re: MPC850 and GDB help

[Ryan Wilkins]

Thanks for the idea.  I'll check it out.

What about running the Linux kernel from ram?  Will I encounter the 
same difficulties?

Thanks,
Ryan Wilkins

On Oct 24, 2004, at 3:33 PM, Frank wrote:

> You probably want to post this to the u-boot users mailing
> lists. Compiling and linking u-boot to run out of ram is not a
> straight forward task. I've done it on more then one board, but
> it is not easy if you're a u-boot novice.
> Search the list for "running out of ram" or something like that
> and you'll see what I mean.:-)

Re: MPC850 and GDB help

[Wolfgang Denk]

In message <002D5C38-25FC-11D9-BA35-0050E4B0DC64@elevated-networks.com> you wrote:
> 
> What about running the Linux kernel from ram?  Will I encounter the 
> same difficulties?

No, this is what Linux is designed for.

But this doesn't help you. Before Linux can run, you need  a  working
boot loader to initialize the hardware.

Before you start you should ask yourself if  you  have  all  required
documentation  available.  You will need a detailed hardware descrip-
tion, which documents which pins of the MPC8xx  are  used  for  which
purpose,  what  board control registers, CPLDs etc. are there and how
they are expected to be initialized, etc.

With all the documentation available, you will need to get a thorough
understanding of the hardware. Only then you  should  try  porting  a
boot loader.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
Carelessly planned projects take three times longer to complete  than
expected.  Carefully  planned  projects  take  four  times  longer to
complete than expected, mostly  because  the  planners  expect  their
planning to reduce the time it takes.

Re: MPC850 and GDB help

[Frank]

I think I may have confused you a little. When I said running
u-boot from ram, I meant booting it from ram as if it had boot
from flash. Normally, at some point, u-boot _will_ run from ram
by copying itslef there and continung to run. But getting it to
run from ram it's reset vector (first linked address + 0x100) is
totally different.
I'm not sure what you mean by "running Linux from ram". Although
the kernel may reside in flash, it is at some point unzipped,
copied to ram and then runs from there. Someone on this list may
be able to help you more here. Maybe you will have beteer luck
then me getting an answer from these guys. They don't seem to
respond to my questions.:-(

--- Ryan Wilkins <ryan@elevated-networks.com> wrote:

> Thanks for the idea.  I'll check it out.
> 
> What about running the Linux kernel from ram?  Will I
> encounter the 
> same difficulties?
> 
> Thanks,
> Ryan Wilkins
> 
> On Oct 24, 2004, at 3:33 PM, Frank wrote:
> 
> > You probably want to post this to the u-boot users mailing
> > lists. Compiling and linking u-boot to run out of ram is not
> a
> > straight forward task. I've done it on more then one board,
> but
> > it is not easy if you're a u-boot novice.
> > Search the list for "running out of ram" or something like
> that
> > and you'll see what I mean.:-)
> 
> 



		
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Re: MPC850 and GDB help

[Ryan Wilkins]

Ahh yes.. I wanted to get u-boot loaded into RAM and running from 
there.  The reason being, I'm having a bit of a hard time writing a 
flash chip definition file in the MPCBDM Flash.def format for the Intel 
DA28F320J5 flash chip.  My thought was to boot u-boot from ram and then 
see if it had better luck at detecting my flash chip and then try to 
coerce it into writing u-boot to flash for me.

As for the "running Linux from ram" thing it was another fleeting 
thought.  Something along the lines of if I can't get u-boot to run 
from ram maybe I could get Linux to boot from ram and then go from 
there.

Anyway, as you can tell I'm in way over my head but I'll figure 
something out.  I've got a bit of raw programming experience with 8-bit 
micros but nothing 32-bit.  I hate to have this MPC850 sitting here 
doing nothing.

Answer me this if you would.. Does the MPC850 have some sort eeprom or 
parameter RAM on-chip that would be remembered in the event of a hard 
reset or power cycle and preclude the chip from booting from flash if 
certain registers were changed?
I'm looking through the manual for the 850 now but don't see anything 
jumping out at me.

On Oct 24, 2004, at 5:50 PM, Frank wrote:

> I think I may have confused you a little. When I said running
> u-boot from ram, I meant booting it from ram as if it had boot
> from flash. Normally, at some point, u-boot _will_ run from ram
> by copying itslef there and continung to run. But getting it to
> run from ram it's reset vector (first linked address + 0x100) is
> totally different.
> I'm not sure what you mean by "running Linux from ram". Although
> the kernel may reside in flash, it is at some point unzipped,
> copied to ram and then runs from there. Someone on this list may
> be able to help you more here. Maybe you will have beteer luck
> then me getting an answer from these guys. They don't seem to
> respond to my questions.:-(

Re: MPC850 and GDB help

[Wolfgang Denk]

In message <77988B3D-260C-11D9-BA35-0050E4B0DC64@elevated-networks.com> you wrote:
> Ahh yes.. I wanted to get u-boot loaded into RAM and running from 
> there.  The reason being, I'm having a bit of a hard time writing a 
> flash chip definition file in the MPCBDM Flash.def format for the Intel 
> DA28F320J5 flash chip.  My thought was to boot u-boot from ram and then 
> see if it had better luck at detecting my flash chip and then try to 
> coerce it into writing u-boot to flash for me.

This is the wrong approach. First understand the problem, and fix it.
You will need exavctly this understanding to be able to port U-Boot.

You MUST go step by step. You cannot leapfrog problems.

> As for the "running Linux from ram" thing it was another fleeting 
> thought.  Something along the lines of if I can't get u-boot to run 
> from ram maybe I could get Linux to boot from ram and then go from 
> there.

No, that would even be trying to jump over more than one problem, and
is all the more bound to fail.

> Answer me this if you would.. Does the MPC850 have some sort eeprom or 
> parameter RAM on-chip that would be remembered in the event of a hard 
> reset or power cycle and preclude the chip from booting from flash if 
> certain registers were changed?

No. There is no information kept in the MPC8xx processor itself after
power-cycling it.  But  depending  on  your  hardware  there  may  be
features like an EEPROM with VPD or programmable BCSR's or even plain
old jumpers.

> I'm looking through the manual for the 850 now but don't see anything 
> jumping out at me.

Check the documentation for your _board_. If you have  it,  that  is.
[And  if  you  don't,  then either give up now or plan for a _lot_ of
frustrating experience.]

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
Boykottiert Microsoft - Kauft Eure Fenster bei OBI!

Re: MPC850 and GDB help

[Ryan Wilkins]

On Oct 24, 2004, at 7:39 PM, Wolfgang Denk wrote:

> This is the wrong approach. First understand the problem, and fix it.
> You will need exavctly this understanding to be able to port U-Boot.
>
> You MUST go step by step. You cannot leapfrog problems.

Understood.  I need to understand a lot of things first.

> Check the documentation for your _board_. If you have  it,  that  is.
> [And  if  you  don't,  then either give up now or plan for a _lot_ of
> frustrating experience.]
>
The board is an ADSL modem that was designed specifically by the ISP.  
The firmware would not allow operation with another ISP and this ISP 
has since gone out of business.  Other than the custom firmware not 
allowing ISP changes, it worked the same as anyone else.  There is no 
documentation publicly available on this board.  This board is based on 
a MPC850 processor, hence the reason I'm trying to get into it.  I 
expect a lot of frustrating experiences trying to get this thing to 
work, but I don't see why I can't work my way through it.  All of the 
solder connections from the 850 to the logic board appear on the 
opposite side of the board directly under the 850.  With any luck, I 
should be able to trace out certain lines to verify what is connected 
to what.  As for the other components present on the board, they're all 
easily identifiable.  I think with a little bit of work, I can load 
u-boot and Linux on this thing.

Thanks for the comments,
Ryan Wilkins