Re: [ECOS] Question on wigglers, debugging Redboot in flash fortheXScale target in single step mode

[Gary Thomas <gary at mlbassoc dot com>]

On Mon, 2004-08-02 at 09:12, Krishna Ganugapati wrote:
> Gary, Thanks for the response.
> 
> I'm afraid I don't quite understand what you're saying..
> 
> a)  > Why do you think this is wrong?  When you reset the board, single
> > stepping (via hardware which is very different that what you describe in
> > item "c" above), you should execute the "reset handler" an instruction
> > at a time.  This is just what is supposed to happen.
> 
> Are you saying that this is correct behavior?

Yes.

> 
> When I hit the reset vector, I'm stuck.. subsequent single steps only keep
> me at the reset vector - I don't advance any further..
> 
> b) How do I debug my redboot image?

Figure out the answer to why single step doesn't progress, then you'll 
be able to debug RedBoot.  You _should_ be able to do this with the
hardware you have, but alas you may have problems.  Given that MacRaigor
doesn't really support OCD and the Wiggler is pretty primitive and ...

You might consider getting a more powerful debug tool, especially if 
debugging hardware [initialization] is new to you.  One of the best
available is the BDI2000 from Abatron, but there are many others.

> -------------------------------------------------
> ----- Original Message ----- 
> From: "Gary Thomas" <gary@mlbassoc.com>
> To: "Krishna Ganugapati" <krishnag@marakicorp.com>
> Cc: <ecos-discuss@sources.redhat.com>
> Sent: Monday, August 02, 2004 7:59 AM
> Subject: Re: [ECOS] Question on wigglers, debugging Redboot in flash forthe
> XScale target in single step mode
> 
> 
> > On Mon, 2004-08-02 at 08:49, Krishna Ganugapati wrote:
> > > Hello,
> > >
> > > I'm looking for some clarification on the following issues.
> > >
> > > Target;: Custom IXP425 XScale (almost identical to the IXDP development
> > > board, minus the highspeed UART and minus the LEDs), Redboot in ROM
> mode.
> > > Debugging interface:  Macraigor Wiggler, OCD Commander for the software
> > > debugger on the host.
> > >
> > > Situation:  I can successfully download my redboot rom image to Flash
> using
> > > the Wiggler and the Macraigor Flash Programmer.
> > > When I reset my target, I connect to the JTAG port using the OCD
> Commander
> > > debugger and attempt to single step through instructions.
> > >
> > > Results
> > >
> > > 1) Through the OCD Debugger, I note that Flash memory is correctly
> relocated
> > > at 0x000000000.
> > > 2) Using the OCD Debugger, I can manual configure the SDRAM registers
> and
> > > determine that my SDRAM acc ANy recess is good. I flip the
> > > EXP_BUS_CONFIGURATION bits that switc SDRAM and Flash around and
> determine
> > > that SDRAM is now located at 0x00000000 - I can successfully read and
> write
> > > words to the first 256 MB so I am assuming memory is good.
> > >
> > > 3) Reset the board, board is now in bootup mode, flash is at 0x00000000.
> I
> > > now attempt to single step through my redboot rom image. On the first
> > > instruction, the board transfers control to the reset handler.
> > >
> > > Questions:
> > >
> > >  a) Has anyone seen behavior like this?
> > > b) On the web it looks like quite a few people have seen something like
> > > this, but there have been no followups on how to fix this.
> > > c) When I reviewed the XScale documentation, it says that when a
> debugger
> > > executes a single step instruction, a debug event handler is expected
> and
> > > that this debug event handler is overloaded at the reset handler. It
> also
> > > says that the debug event handler code needs to be downloaded to the
> target
> > > through the JTAG. Questions:
> > >     i) Does the OCD Commander software debugger  interface actually
> download
> > > a debug event handler? If it does, then my conclusions are wrong and I
> have
> > > to look elsewhere for why things in single step are not progressing, but
> if
> > > I'm right, then perhaps I need a more sophisticated debugger for my JTAG
> > > interface (the OCD Commander is free). Any recommendations
> >
> > Why do you think this is wrong?  When you reset the board, single
> > stepping (via hardware which is very different that what you describe in
> > item "c" above), you should execute the "reset handler" an instruction
> > at a time.  This is just what is supposed to happen.
> >
> > >
> > > Other clarifications:
> > > 1) One thing that was not very clear in XScale little endian vs big
> endian
> > > modes was the opcode fetch modes for the XScale. After investigating, my
> > > understanding is that whether in big endian or in little endian mode,
> > > XScale opcode fetches are always in little endian mode. Which is why
> when
> > > you build a big endian target for the XScale IXP425 board which
> generates
> > > the instructions in big endian mode, you need to byte swap the image. Is
> > > this correct?
> > >
> > > Thanks for any input.
> > >
> > > Krishna
> > -- 
> > Gary Thomas <gary@mlbassoc.com>
> > MLB Associates
> >
-- 
Gary Thomas <gary@mlbassoc.com>
MLB Associates


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