From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <support@abatron.ch>
Received: from vm-3.internezzo.ch (vm-3.internezzo.ch [195.234.43.35])
 by ozlabs.org (Postfix) with SMTP id BDB42B6FA4
 for <linuxppc-dev@ozlabs.org>; Thu, 31 May 2012 19:31:13 +1000 (EST)
Date: Thu, 31 May 2012 11:30:57 +0200
From: Abatron Support <support@abatron.ch>
Message-ID: <13517672561.20120531113057@abatron.ch>
To: Joakim Tjernlund <joakim.tjernlund@transmode.se>
Subject: Re[4]: [RFC] [PATCH] powerpc: Add MSR_DE to MSR_KERNEL
In-Reply-To: <OF53CDE18C.59DD377E-ONC1257A0F.0031C7A0-C1257A0F.0031EA81@transmode.se>
References: <1338363814-19565-1-git-send-email-Joakim.Tjernlund@transmode.se>
 <6F7E3816-E71B-466A-9C6F-9928E1CFD7B1@digitaldans.com>
 <10126984030.20120530140826@abatron.ch>
 <OF53CDE18C.59DD377E-ONC1257A0F.0031C7A0-C1257A0F.0031EA81@transmode.se>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: linuxppc-dev@ozlabs.org, Dan Malek <ppc6dev@digitaldans.com>,
 Bob Cochran <ppc@mindchasers.com>
Reply-To: Support <support@abatron.ch>
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>


> Abatron Support <support@abatron.ch> wrote on 2012/05/30 14:08:26:
>>
>> >> I have tested this briefly with BDI2000 on P2010(e500) and
>> >> it works for me. I don't know if there are any bad side effects,
>> >> therfore
>> >> this RFC.
>>
>> > We used to have MSR_DE surrounded by CONFIG_something
>> > to ensure it wasn't set under normal operation.  IIRC, if MSR_DE
>> > is set, you will have problems with software debuggers that
>> > utilize the the debugging registers in the chip itself.  You only want
>> > to force this to be set when using the BDI, not at other times.
>>
>> This MSR_DE is also of interest and used for software debuggers that
>> make use of the debug registers. Only if MSR_DE is set then debug
>> interrupts are generated. If a debug event leads to a debug interrupt
>> handled by a software debugger or if it leads to a debug halt handled
>> by a JTAG tool is selected with DBCR0_EDM / DBCR0_IDM.
>>
>> The "e500 Core Family Reference Manual" chapter "Chapter 8
>> Debug Support" explains in detail the effect of MSR_DE.

> So what is the verdict on this? I don't buy into Dan argument without some
> hard data.

What I tried to mention is that handling the MSR_DE correct is not only
an emulator (JTAG debugger) requirement. Also a software debugger may
depend on a correct handled MSR_DE bit.

Ruedi