Re: [ECOS] eCosCentric Cortex-M port contribution

[Nick Garnett <nickg at ecoscentric dot com>]

"simon.kallweit@intefo.ch" <simon.kallweit@intefo.ch> writes:

> 
> Ok, I guess the issues you're talking about are not related to the
> silicon errata just release by STMicroelectronics, concerning some
> compilers generating incompatible code with all but the latest
> revisions of the STM32 processors?

No they are not. ST is annoyingly vague about exactly what the
problems are in that erratum, but the description bears no relation to
the issue we have. In any case, that erratum refers to medium-density
devices while the part on the eval board is high-density. Of course I
don't know what density device or revision you are using for your
own hardware, but it is probably worth ensuring you get parts that
avoid this issue.

> It occurred to me, now that I have been digging into the subject more
> deeply, that there are some issues concerning the design of the
> Cortex-M3 to match with ecos. I think I do understand the design of
> how a kernel should work under the Cortex-M3 architecture, but
> admittedly I don't quite see yet how to do that efficiently with
> ecos. Does your solution come with changes in the generic ecos kernel
> code, or did you manage to solve it all in the Cortex-M3 HAL?

It is all solved entirely in the Cortex-M HAL. Like you I initially
thought that eCos would fit quite nicely. However, the priority
mechanism, the strict enforcement of exception nesting and some other
things mean that the obvious approach didn't work. You either ended up
throwing a hard fault exception, or ended up with all interrupts
masked. I believe my eventual solution is quite elegant, but it was
won at the expense of some false starts.


> Of course, it might make more sense to just wait for you to release
> the port, but this puts us on hold for an uncertain amount of time, as
> you don't make a clear statement of when the release will be. So I
> think it would be great to start working with your port, as I guess
> it's pretty sure that even if I continue developing and get a working
> solution myself, it will be your port that ends up in the official
> ecos community repository. So my past and future work will be quite
> obsolete, despite the learning I did :(

The exact release date depends on whether any serious problems are
thrown up in testing and how quickly we can deal with the remaining
toolchain issues.

Everything you have learned so far will still be useful, so nothing
has been wasted :-)


-- 
Nick Garnett                                      eCos Kernel Architect
eCosCentric Limited    http://www.eCosCentric.com      The eCos experts
Barnwell House, Barnwell Drive, Cambridge, UK.     Tel: +44 1223 245571
Registered in England and Wales:                        Reg No: 4422071


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