On Thu, Jan 26, 2012 at 8:49 AM, Peter Stuge <[email protected]> wrote:
> dave higton wrote:
>> Which is not supported: SWD or Cortex-M0?
>
> SWD first and foremost. Since M0 have no JTAG this also means that M0
> is not supported of course.
>
>
>> Are there plans to add support?
>> Is anyone working on it?
>
> Three efforts deal with SWD in OpenOCD:

0. As an historical note, I had SWD in OpenOCD up and running, as a
proof-of-concept, over three years ago. The OpenOCD code base has seen
massive improvements since then but SWD is, strangely enough, still
officially lacking.

> 1. David Brownell started an effort to access Luminary Micro ARM CM3
>   chips via SWD. These chips support both SWD and JTAG. David passed
>   away during spring 2011.
>
> 2. Simon Qian has OpenOCD patches to make SWD work using his Versaloon
>   adapter, but without adding generic support for SWD concepts in
>   OpenOCD. I believe Simon still maintains this patch, although last
>   time I checked the Versaloon forum it was unfortunately offline.
>
> 3. Tomek started working on libswd to create a generic SWD
>   implementation and maybe also as an experiment to see how SWD
>   concepts can fit into OpenOCD without needing to rewrite OpenOCD
>   from scratch. I believe Tomek has some working code, but I have
>   not yet done any testing. I think Tomek focuses on FT2232-based
>   adapters. I very much welcome also having Versaloon support in
>   libswd.
>
>
>> How big a job is it?
>
> I can't say. It's a problem that OpenOCD is based on an assumption of
> JTAG.

Indeed. I have some, still rather vague, ideas on how to change that.
I'm planning on exploring them in a not too distant future. As always,
my ideas are rather ambitious; I don't think it's fun building on code
that I know is architecturally broken. So we'll see if anything useful
comes out of it. I don't know how libswd would fit into that picture
(the one in my head) but then I haven't had the time to look at
Tomek's work at all. I have to say I'm a bit sceptical since having a
protocol as a library suggests that it is placed somewhere *between*
the target and the interface. Much like the current JTAG queue, which
will be the first thing to go once I start hacking.

/Andreas

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