[ECOS] Redboot causes PCI abort in Linux Ixp425

Stephen Goadhouse stephen.goadhouse@adiengineering.com
Thu Mar 16 15:49:00 GMT 2006


Xscale processors, and perhaps other ARM-based processors, will get a
data abort exception while scanning the PCI bus.  This is normal.  To
scan the bus, the system should be trying to read every available PCI
configuration slot address to see if a device is there.  If no device is
there, you'll get a data abort exception because technically the PCI
transaction did not complete (no target to handle the PCI configuration
read).  Typically, this is handled by installing a data abort exception
handler prior to scanning the bus that gracefully handles these
exceptions during PCI bus scan.  Another alternative with the IXP425 may
be to setup its internal PCI bridge so that it returns 0xFFFFFFFF instead
of doing a data abort.  I have not looked at the ixp425 manual in a
while, but I am fairly certain that it has this ability.  I would expect
that's what your old RedBoot did to handle this so that Linux would not
have to.  Receiving 0xFFFFFFFF when reading non-existent PCI slots is
what happens in a PC environment and I'm fairly certain that is what
Linux typically expects.   


_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/  
_/  Stephen Goadhouse                 Work: (434) 978-2888 x254 _/
_/  Senior Staff Engineer  stephen.goadhouse@adiengineering.com _/
_/  ADI Engineering               http://www.adiengineering.com _/
_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ 


> -----Original Message-----
> From: ecos-discuss-owner@ecos.sourceware.org 
> [mailto:ecos-discuss-owner@ecos.sourceware.org] On Behalf Of 
> Ravi modgekar
> Sent: Thursday, March 16, 2006 1:04 AM
> To: ecos-devel@sourceware.org; ecos-discuss@sourceware.org
> Subject: [ECOS] Redboot causes PCI abort in Linux Ixp425
> 
> Hi,
>    I have an  IXP425 based board based on Gateworks
> GW2345 board.This
> board already had a redboot image programmed  through which 
> we could easily load linux and work on it.
>   Now I have compiled the redboot for our IXP based board 
> from the Avila redboot sources.With this newly compiled 
> redboot I am able to
> boot linux, but unfortunately the PCI   cribs and the
> linux crashes
> with PCI abort. The error message being "!!!
> abort_handler addr =
> 0x40015000 ,isr = 0x0 , status = 0x22a0".
> Interestingly the same Linux
> image works fine with the old redboot ,for which we don't 
> have the source code.
>   Has anybody in this list faced this problem.Am I missing 
> configuring something in the Redboot  which is causing the 
> PCI abort.I have tried with completely disabling PCI 
> interface , but I still see this problem.
> 
>  any pointers !!!
> 
> Regds
> Ravi
> 
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