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From: Detlev Zundel <dzu@denx.de>
To: linuxppc-embedded@ozlabs.org
Subject: Re: Breakpoint is not hitting for Kernel Debugging
Date: Wed, 05 Sep 2007 15:27:22 +0200	[thread overview]
Message-ID: <m2wsv58cp1.fsf@ohwell.denx.de> (raw)
In-Reply-To: 7c1681440709032107u3feb0684x34dcf44b5e43616@mail.gmail.com

Hi,

> Try adding this line to your BDI config to clear/invalidate the page
> table base address so that the MMU translation works before the MMU
> has been initialised.
>
>   ;; Following is to clear the page table base address
>   WM32    0x000000f0      0x00000000

Did you really need this under any circumstance?  To only hit a
breakpoint?

I am asking because recent experiences with BDI debugging showed that
there are some pitfalls that one can fall into (and these are only the
ones that I got aware of):

a) - PTBASE is 0x00 (!) for head_fsl_booke, head_44x,
   - PTBASE is 0xf0 for head_4xx

   Don't ask me if this makes any sense, but that's how it is right
   now.

   So for the original poster I would say a PTBASE 0x0 would be in
   order.

b) Moreover even with a _wrong_ PTBASE on a 440EPx the BDI translated
   start_kernel just fine by only subtracting 0xc0000000 (using a
   "default" translation) - it was only later (debugging dynamic
   modules) that the wrong PTBASE hit me hard.

What proved very useful for me is the bdi command "phys <addr>" to
check the translation the BDI uses [you can use the command (as all
BDI commands) through gdb with "mon phys <addr>" btw.] - a wrong
PTBASE led to subsequent "JTAG instruction overruns" so I was pretty
sure that this was my real problem.

Best wishes
  Detlev

-- 
The limits of my language stand for the limits of my world.
                                        -- Ludwig Wittgenstein
--
DENX Software Engineering GmbH,      MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich,  Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-40 Fax: (+49)-8142-66989-80 Email: dzu@denx.de

  reply	other threads:[~2007-09-05 13:27 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-09-03 14:02 Breakpoint is not hitting for Kernel Debugging dnl
2007-09-03 19:20 ` Dan Malek
2007-09-04  4:07 ` Bill F
2007-09-05 13:27   ` Detlev Zundel [this message]
2007-09-05 16:31     ` Dan Malek

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