David Brownell wrote:
> On Monday 12 October 2009, Michael Schwingen wrote:
>   
>>> I'll ask the folk using XScale to sanity check; I doubt this
>>> set of XScale patches would have broken anything, but I can
>>> only test on this one ancient PXA255 board I've got.
>>>       
>> I just made a short test on IXP425 - compiled & installed current head,
>> attached to target & tested single-step - seems to work fine, without
>> the previous manual-copy-debug-handler-step.
>>     
>
> Thanks for checking.
>
> How stable do you find the XScale support, by the way?
>   
Looks quite stable to me. I use it regularly at home on IXP42x (I have a
BDI2000 at work), mostly in the mode of "reset halt / erase & program
flash / reset run", plus from time to time some gdb-based debugging. I
had some problems with breakpoints, but forcing hard breakpoints seems
to fix that.

Debugging inside the Linux kernel seems a bit tricky for now.

> I found a write-to-old-stackframe bug, and checked in a
> fix for it ... that may have made things a bit better,
> but it's hard to tell since the behavior varies wildly.   
>
> Seeing that this is almost the only driver that uses
> the code to validate DR scans -- and observing those
> warning firing pretty regularly -- says to me that
> some strange behavior is common here.
>
> I've observed two reset-related problems.  One is that
> the initial "reset" (from TCL command line) will not
> often work.  I've got a workaround I'm not yet ready
> to send around.  My theory is that the original work
> on this code was on a second generation core (PXA270,
> like your IXP425 -- 7 bit IR length) while this first
> generation core (PXA255) is a bit more finickey.
>   
I have not had any reset problems or instabilities on IXP42x for quite
some time now (longer back than 0.2.0 release). I have used both Rev.
2.0 and Rev. 2.1 IXP42x CPUs, although I think there is no real
difference in the core.

> The second is that the *second* reset won't work at all.
> AND ... this seems like something any XScale should
> be seeing.  The root cause being that it won't reload
> the debug handler after it's purged from the mini-icache.
> (TRST clears DCSR.H ... and SRST purges the mini-icache
> unless that bit is set.  QED.)
>
> Have you observed that problem with the second reset?
>   

What kind of "second"?

Using "reset halt" or "reset run" multiple times without re-starting
OpenOCD works fine for me.

cu
Michael

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