Lockup when using three or more TX2plus/PDC20375 cards

[Ian Oliver <lists@foxhill.co.uk>]

Hi,

I am using Ubuntu Hoary with the standard 2.6.10 kernel.
I have 4x Maxtor SATA cards using the PDC20375 (rebranded Promise 
TX2plus) in PCI slots. Each drive is cabled to 2 SATA HDs and these are 
used as two groups of four for software raid using mdadm. Boot drive is 
a non-raid PATA drive.

When I really hammer the sw raid that's on two of the cards it will 
generate lots of these in the log -
Jul 25 17:33:42 localhost kernel: ata7: status=0x51 { DriveReady 
SeekComplete Error }
Jul 25 17:33:42 localhost kernel: ata7: error=0x0c { DriveStatusError }

then I get the following on the console -
ata7: command timeout
and then the whole machine locks solid.

I can do whatever I like to the raid on the 1st four cards and it seems 
rock solid.

I hear talk of 3rd and subsequent cards not being initialised by the 
BIOS, and my "lspci -v" results back this up. (Please see 
http://bugzilla.ubuntu.com/show_bug.cgi?id=13046 rather than cluttering 
this list.)

How can I address this problem? I have just built a 2.6.10 kernel and 
modules (very much a first for me) so I think I can apply patches and 
try things out.

Note that I think Ubuntu has some patches from later kernels applied to 
their libata to add pass through, but I don't know the status of the 
sata_promise.

Regards

Ian