Re: Initialize DBCR0 for PPC440 targets

[srikanth krishnakar <skrishnakar@gmail.com>]

Hi David,

Just to correct the statements : How the DBCR0 is initialized on
targets that don't use boot loaders ?

-Srikant

On Wed, May 20, 2009 at 11:30 AM, David Gibson
<david@gibson.dropbear.id.au> wrote:
> 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-td2304=
9044.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. =A0It'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. Thi=
s
>> >> 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 havin=
g
>> >> 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=3D=3D0.
>
> --
> David Gibson =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| I'll have my music =
baroque, and my code
> david AT gibson.dropbear.id.au =A0| minimalist, thank you. =A0NOT _the_ _=
other_
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| _way_ _a=
round_!
> http://www.ozlabs.org/~dgibson
>



--=20
"The Good You Do, The Best You GET"

Regards
Srikanth Krishnakar
**********************