Raspberry Pi BSP debugging

[Alan Cudmore]

It looks like the CP15 initialization is explicitly enabling unaligned
traps, so that is the likely cause.
The BSP has a good polled printk, so I might try to setup something for the
exception vectors as well.
Thanks,
Alan



On Wed, May 1, 2013 at 1:11 PM, Claus, Ric <claus at slac.stanford.edu> wrote:

> It's not clear what your debugging environment is like, but if you could
> put some sort of indicator (e.g. a printk, a write to memory that is
> persistent across reboots, or turn on an LED) in each of the exception
> vectors (except IRQ, since it will be tickled often by at least clock),
> then you could tell whether you've taken an exception.  It smells like
> you're taking an alignment exception and landing in a for (;;) loop.
>
> It'd interesting to know the pros and cons of enabling unaligned accesses
> with CP15.  Naively, it might seem like a good idea to always enable these.
>  Presumably it kills performance to do so, however.
>
> Ric
>
> ________________________________________
> From: rtems-users-bounces at rtems.org [rtems-users-bounces at rtems.org] On
> Behalf Of Alan Cudmore [alan.cudmore at gmail.com]
> Sent: Wednesday, May 01, 2013 8:12 AM
> To: Gedare Bloom
> Cc: rtems-users at rtems.org
> Subject: Re: Raspberry Pi BSP debugging
>
> Great idea. It should be easy enough to try, and it looks like the bit to
> enable unaligned access is not set in the BSP.
>
> Thanks,
> Alan
>
>
>
> On Wed, May 1, 2013 at 10:38 AM, Gedare Bloom <gedare at rtems.org<mailto:
> gedare at rtems.org>> wrote:
> Could it be a matter of the compiler (not) knowing the correct
> alignment for the target architecture?
>
> To quote Sebastian from a recent post: "Please have a look in the
> ARM1176JZF-S manual.  You may have to enable the unaligned access in
> the CP15."
>
> -Gedare
>
> On Wed, May 1, 2013 at 10:16 AM, Alan Cudmore <alan.cudmore at gmail.com
> <mailto:alan.cudmore at gmail.com>> wrote:
> > I'm trying to track down a bug in the Raspberry Pi BSP. It will be much
> > easier once I get a JTAG device, but for now I have been able to narrow
> down
> > one specific instance where the BSP hangs.
> >
> > The first symptom of this problem was with a shell example. If I type an
> > invalid shell command, I noticed it will hang or crash on the strncat
> > function.
> >
> > Next, I modified the simple hello world sample and found that it will
> also
> > hang with a strncat call. I copied the strncat function from the newlib
> > sources and found that the local copies ( optimized for size and speed )
> > work. The attached example shows the two local strncat calls followed by
> the
> > newlib call. It will always hang on the newlib call.
> >
> > This example works on the arm920/gdb simulator and the sparc-sis
> simulator.
> >
> > Some other notes;
> > - The memory map looks reasonable, comparing it to the arm920 map
> > - Many other newlib functions work such as strncpy, printf, etc
> > - Much of the other basic RTEMS seem to work as well. I can create a RAM
> > disk, format it , mount it, copy files, etc. I ran many of the tests
> such as
> > unlimited, ticker, etc.
> >
> > If anyone has an idea I can try let me know. Otherwise I might just wait
> > until I can get a JTAG device hooked up.
> >
> > Thanks,
> > Alan
> >
> >
> >
> >
> >
> >
> > _______________________________________________
> > rtems-users mailing list
> > rtems-users at rtems.org<mailto:rtems-users at rtems.org>
> > http://www.rtems.org/mailman/listinfo/rtems-users
> >
>
>
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