From: Jerry Van Baren <gvb.linuxppc.dev@gmail•com>
To: Jon Smirl <jonsmirl@gmail•com>
Cc: Olof Johansson <olof@lixom•net>, linuxppc-dev@ozlabs•org
Subject: Re: Hardware debuggers for PPC74xx G4 CPUs
Date: Wed, 14 Nov 2007 20:35:52 -0500 [thread overview]
Message-ID: <473BA278.2000402@gmail.com> (raw)
In-Reply-To: <9e4733910711131732i5ec5d226r4037e42399c38f59@mail.gmail.com>
Jon Smirl wrote:
> On 11/13/07, Benjamin Herrenschmidt <benh@kernel•crashing.org> 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
next prev parent reply other threads:[~2007-11-15 1:33 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-13 21:48 Hardware debuggers for PPC74xx G4 CPUs Gerhard Pircher
2007-11-13 21:57 ` Grant Likely
2007-11-13 21:59 ` Grant Likely
2007-11-13 22:10 ` Jon Smirl
2007-11-13 22:21 ` Gerhard Pircher
2007-11-14 1:17 ` Benjamin Herrenschmidt
2007-11-14 9:20 ` Gerhard Pircher
2007-11-13 23:23 ` Dan Malek
2007-11-13 23:39 ` Olof Johansson
2007-11-13 23:53 ` Jon Smirl
2007-11-14 1:17 ` Benjamin Herrenschmidt
2007-11-14 1:32 ` Jon Smirl
2007-11-15 1:35 ` Jerry Van Baren [this message]
2007-11-15 2:34 ` Jon Smirl
2007-11-18 0:47 ` Wolfgang Denk
2007-11-22 23:37 ` Benjamin Herrenschmidt
2007-11-23 0:00 ` Jon Smirl
2007-11-23 0:22 ` Benjamin Herrenschmidt
2007-11-23 15:03 ` Jon Smirl
2007-11-23 20:26 ` Jon Smirl
2007-11-23 20:30 ` Grant Likely
2007-11-13 22:03 ` Jon Smirl
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