BAD_SG_DMA panic in aha1542

[Bob Tracy]

I previously reported an ISA DMA issue for the 2.6.12 kernel.  The issue
persists through at least 2.6.18.  SCSI controller is an Adaptec
AHA-1542B (ISA).

The action "mount -t iso9660 /dev/scd0 /mnt/cdrom -r"

produces

(cdrom detection messages as various modules autoload, then...)
sgpnt[0:1] page c1ee5af0/0x1ee5af0 length 32
Kernel panic - not syncing: Buffer at physical address > 16 Mb used for aha1542

As before, no problems using the sda hard disk (which is the boot drive):
everything works reliably until I touch the cdrom drive.

I'll be happy to assist with the debugging, but the system with the
aha1542 has no development facilities, i.e., I'll have to build test
kernels on a different system, and turnaround is going to be slow :-(.

Thanks in advance for helping me get this old machine working again.
No issues with 2.4 kernels.  I have no idea about 2.5 kernels and
2.6 kernels prior to 2.6.12.  As for why I didn't report this before
now, the aha1542b was in my parts bin until I cobbled a system together
approx. two weeks ago, mostly to see if a useful system could still be
had using legacy hardware and modern GNU/Linux software.  I'm happy to
report the answer is mostly "yes".

-- 
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Bob Tracy                   WTO + WIPO = DMCA? http://www.anti-dmca.org
rct@xxxxxxxx
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