Re: Initialize DBCR0 for PPC440 targets

[David Gibson <david@gibson.dropbear.id.au>]

On Wed, May 20, 2009 at 11:20:46AM +0530, srikanth krishnakar wrote:
> Hi David,
> 
> I am not sure how the IDM behaves on few of PPC440 targets which don't
> have boot loaders. I have a reference for your question:
> 
> http://www.nabble.com/Question-about-DBCR0-initialization-for-440-td23049044.html
> 
> Without this fix (given patch) I am facing problems with GDB, and
> further target hangs while running gdbserver !

That doesn't answer my question.  It's not enough to say "this fixes a
problem" you need to explain *how* it fixes the problem.

And I don't see why IDM would have any effect on *software*
breakpoints.

> On Wed, May 20, 2009 at 5:23 AM, David Gibson
> <david@gibson.dropbear.id.au> wrote:
> > On Tue, May 19, 2009 at 06:38:53PM +0530, srikanth krishnakar wrote:
> >> Hi,
> >>
> >> kernel- 2.6.29
> >> Debug technique: KGDB
> >>
> >> The PowerPC kernel does not initialize the PPC440 DBCR0 register. This
> >> prevents the use of software breakpoints in case of internal debug
> >> mode. Looking into head_fsl_booke.S for initialization of DBCR0 is
> >> used by boot-loaders.
> >> It seems head_44x.S lacks this step of DBCR0 register initialization.
> >> So fixing this with initializing the DBCR0 register as shown below :
> >>
> >> Subject: [PATCH] powerpc: 44x: Initialize DBCR0 for targets not having
> >> bootloader
> >>
> >> The kernel does not initialize the PPC440 DBCR0 register.
> >> This prevents (among other things) the use of software
> >> breakpoints with GDB. The boot loaders probably do initialize
> >> this but few targets run without a boot loader
> >
> > Um.. how does this prevent the use of software breakpoints with gdb?
> > The trap instructions still work with IDM==0.

-- 
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