From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from QMTA03.westchester.pa.mail.comcast.net (qmta03.westchester.pa.mail.comcast.net [76.96.62.32]) by ozlabs.org (Postfix) with ESMTP id 93396DDDE6 for ; Thu, 15 Nov 2007 12:33:39 +1100 (EST) Message-ID: <473BA278.2000402@gmail.com> Date: Wed, 14 Nov 2007 20:35:52 -0500 From: Jerry Van Baren MIME-Version: 1.0 To: Jon Smirl Subject: Re: Hardware debuggers for PPC74xx G4 CPUs References: <20071113214845.85820@gmx.net> <20071113233906.GA32689@lixom.net> <9e4733910711131553ked87330ubc0c439c42e51ace@mail.gmail.com> <1195003078.28865.18.camel@pasglop> <9e4733910711131732i5ec5d226r4037e42399c38f59@mail.gmail.com> In-Reply-To: <9e4733910711131732i5ec5d226r4037e42399c38f59@mail.gmail.com> Content-Type: text/plain; charset=us-ascii; format=flowed Cc: Olof Johansson , linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Jon Smirl wrote: > On 11/13/07, Benjamin Herrenschmidt wrote: >>> That's why Dominic wants to get OpenOCD running on the PowerPC. All we >>> need is the programming documentation for controlling the CPU via the >>> debug hardware. >> Note that this is basically different for every CPU around. > > I'd like to get it for the MPC5200 because of the project I am working > on, an open source audio device. It would be nice if there was a cheap > hardware debugger available for hackers to use on it. Maybe one of the > Freescale developers will see this and send me the right docs. > > Is it radically different? Dominic has been able to support every ARM > 7/9 chip he can get his hands on without too much trouble once the > core support was written. I don't think he has ARM 11 working yet. > >>> Obviously this documentation exist, all of the commercial vendors had >>> to have it to develop their debuggers. Maybe it is already out there >>> and we just don't know where to look. >> Ben. DISCLAIMER: Extrapolating grossly from almost no knowledge! My understanding is that the Freescale PPC debugger interface is based on the JTAG interface using a proprietary command set. Basically, if you do their magic BDM (JTAG extension) command, you get into an internal scan chain that allows you to read/write the processor internals (registers). The problems are many... * The documentation is only available under NDA, a problem for open source debuggers. * The scan chain is different on every processor, and may be different on different revisions of the same processor. * If you mess up with JTAG, you will probably burn up the CPU. Very literally. I've seen it done. Twice. (Thankfully not my screwup, and it wasn't a PPC so it deserved to die. ;-) The internal scan chain is probably safer, but YMMV. gvb