Subject: strange, spurious seeming vector exception on pxa300

From: [email-masked] (Yeasah Pell)
Date: Wed, 02 Dec 2009 11:39:10 -0500

Daniel Mack wrote:
> On Wed, Dec 02, 2009 at 03:50:57PM +0000, Russell King - ARM Linux wrote:
>>
>>
>> Given that the conditions are clearly wrong for a vector exception, I would
>> say that you're hitting some kind of hardware bug - maybe caused by a dirty
>> power supply to the PXA, causing it to misbehave?
>>     

Of course I desperately want to believe this, as then I can ignore all 
this insanity and move on, but it's a bit difficult to swallow that some 
kind of hardware issue would cause a failure that is so consistent (same 
instruction every time, regardless of physical/virtual memory locations, 
compilation flags, etc.) yet caused absolutely no other perceptible 
problems...

> We've had trouble of that kind as well some month ago with an early
> prototype. It wasn't an exception we got, but the bug was clearly
> hitting the same code path every single time, so this issue might be
> related. Eventually it went away with new board revision which made wire
> patching around the DDR SDRAM unnecessary (i.e, cleaner signal pathes).
>
> Strange enough, I would have expected such flaws to cause processor
> misbeviour of all sorts, totally random and unpredictable. The fact that
> is was the same function we always ended up in is still some kind of
> miracle I can't explain.
>
> Daniel
>   

...and having some anecdotal evidence of that kind of situation 
happening is helpful.

Thanks, guys.