From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <skrishnakar@gmail.com>
MIME-Version: 1.0
In-Reply-To: <20090519235302.GA6333@yookeroo.seuss>
References: <6213bc560905190608j73f4191fxbd94158a2b1740c0@mail.gmail.com>
	<20090519235302.GA6333@yookeroo.seuss>
Date: Wed, 20 May 2009 11:20:46 +0530
Message-ID: <6213bc560905192250w4caa84aem9c0dedb2eed72fea@mail.gmail.com>
Subject: Re: Initialize DBCR0 for PPC440 targets
From: srikanth krishnakar <skrishnakar@gmail.com>
To: srikanth krishnakar <skrishnakar@gmail.com>, Linuxppc-dev@ozlabs.org,
	Linuxppc-embedded@ozlabs.org
Content-Type: text/plain; charset=ISO-8859-1
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.ozlabs.org>
List-Unsubscribe: <https://ozlabs.org/mailman/options/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=unsubscribe>
List-Archive: <http://ozlabs.org/pipermail/linuxppc-dev>
List-Post: <mailto:linuxppc-dev@ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@ozlabs.org?subject=help>
List-Subscribe: <https://ozlabs.org/mailman/listinfo/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=subscribe>

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-td2304904=
4.html

Without this fix (given patch) I am facing problems with GDB, and
further target hangs while running gdbserver !

Thanks,
Srikanth

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=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
**********************