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Date: Mon, 06 Jan 2003 09:16:53 -0700
From: "Justin T. Gibbs" <gibbs@scsiguy.com>
To: dipankar@in.ibm.com
cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: aic7xxx broken in 2.5.53/54 ?
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> Hi Justin,
> 
> On Fri, Jan 03, 2003 at 08:14:06AM -0700, Justin T. Gibbs wrote:
>> > Looks like the aic7xxx driver in 2.5.53 and 54 are broken on my
>> > hardware.
>> 
>> It looks like the driver recovers fine.
> 
> Not for long. It dies shortly afterwards.

In what fashion?

>> > aic7xxx: PCI Device 0:1:0 failed memory mapped test.  Using PIO.
>> > Uhhuh. NMI received for unknown reason 25 on CPU 0.
>> 
>> SERR must be enabled by your BIOS.  I will change the driver so
>> that, should the memory mapped I/O test fail, an SERR (and thus an
>> NMI) is not generated.
> 
> I guess having to use PIO with aic7xxx is bad. MMIO failure is
> what we need to investigate.

The only way that I know how to investigate these issues is
with a PCI bus analyzer.  We're in the process of going through
all of the systems we have in our lab to see which ones fail and
why, but I certainly don't have one of every failing system on
the planet. 8-)

>> Just out of curiosity, do you have any strange PCI options enabled
>> in your BIOS?  I remeber seeing memory mapped I/O failures on this
>> ServerWorks chipset under FreeBSD in the past, but an updated BIOS
>> resolved the issue for the affected users.  It seemed that the BIOS
>> incorrectly placed the Adaptec controller in a prefetchable region.
>> 
> 
> I didn't change anything in that box since it was delivered to me. FYI
> it is an IBM x250. Would it help if I can get a PCI space dump and mtrr 
> dump ? FWIW, the older driver works fine. Does the older driver use 
> only PIO ?

It would be good to know the chipset on the motherboard.  As to why
the old driver worked, for 6.X.X drivers, you may have just been lucky.
For 5.X.X drivers, they perform a read after every register write to
"manually" prevent any byte-merging.  These reads are actually more
expensive than just using PIO.  Neither of these older drivers included
a test to try and catch fishy behavior.

--
Justin
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