Xilinx IP core drivers for RTEMS- diff attached
kjrobert at alumni.uwaterloo.ca
Tue Dec 5 22:21:39 UTC 2006
gregory.menke at gsfc.nasa.gov wrote:
> I finally got back to some long-needed config management on the gen405
> bsp. I assembled the diffs against 184.108.40.206, the file is attached for
Thanks for this Greg.
> I hesitate to just check them in as some of the changes related to
> uarts, fpu and memory map are highly idiosyncratic and I don't want to
> mess up other people's work. I think a compromise patch might make the
> most sense, where I set up a diff that preserves the general character
> of the bsp; base addresses, etc.. but gets in the updated drivers.
I'm in favour of this being checked straight into a new xilinx or virtex
405 bsp. This could be a straight branch of the gen405 bsp with the
combination of your and my changes applied. This can be done without
breaking any existing clients and allows us a simpler merge/update
procedure. Does this sound ok to you?
> Our bsp was peculiar in that the 405 units have 4 uarts and no fpu at
> all, meaning, the entire toolchain has to be compiled with -msoft-float
> to ensure nothing at all in newlib or above uses fp registers- the
> va_args are problematic since the ppc ABI allows fpu registers to be
> used when handing variable arguments.
Hmmm.. I'm quite interested in this. We don't have a fpu either
(straight xilinx virtex2/4 ppc405) and I haven't given gcc the
-msoft-float option. However, despite some searching through assembly
listings, I've never found any fp instructions/registers being emitted.
We've also had a number of different board variants in use for well
over a year with no illegal instruction exceptions and the like. ISTR
Till and others have problems with this on the higher spec ppc's.
However, until now I didn't now it was a problem on the ppc405.
Did you find cases where newlib/va_args (both of which we're also using)
generated fp instructions?
> I think it is this issue that
> generally forces all PPC tasks to be floating point- its quite an
> annoying architectural property.
I'm confused. If you compiled with -msoft-float then presumably the
tasks don't need to be floating point as no special registers would need
to be saved during task switches? Do I not fully understand something?
To summarise, we are successfully using the virtex ppc405 with:
- no explicit c floating point types
- no fpu
- no floating point tasks
- no -msoft-float
- with newlib
- with va_args
- with rtems' gcc-3.2.3
and I haven't (yet) found any fp instructions being generated.
Have I just got lucky and this is an issue I really need to look into?
> So I'd like to propose that folks interested in the Virtex 4 gen405 bsp
> family have a look at the diffs and respond with issues & changes and
> hopefully I can commit something that doesn't cause too much trouble.
Your diffs don't include the any changes/additions for _init/_fini. See
http://www.rtems.com/ml/rtems-users/2005/july/msg00008.html and related
posts for more info.
Have you got this port to work successfully without this patch? If so,
I'd be quite keen to understand how.
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