Non aligned DMA transfer errors with k3b

Mike Clarke jmc-freebsd at milibyte.co.uk
Sun May 25 20:22:44 UTC 2008


Suddenly today all my attempts to burn DVDs with k3b result in a 
continuous stream of the following error messages.

May 25 18:04:40 kestrel kernel: ata1: FAILURE - non aligned DMA transfer 
attempted
May 25 18:04:40 kestrel kernel: acd0: setting up DMA failed

Quiting k3b doesn't stop the flood of errors, reboots hang and the only 
solution is to hit the reset switch.

I'm running 7.0 RELEASE and if I reboot into my 6.3 partition k3b works 
just fine, confirming that it's not a media or hardware fault. I've 
also replaced the DVD writer but I still get the problem with 7.0.

I can burn the same data to the same DVD with growisofs with no problem 
which suggests that the problem lies with k3b so this got me wondering 
if it was related to the massive portupgrade I did yesterday (affecting 
156 ports) but that seems unlikely because when portupgrade finished 
last night I rebooted and burnt that day's backup to DVD+RW without 
problem. This morning I burnt 3 DVD+Rs without problem, then about an 
hour later the problem suddenly appeared when I started to burn another 
DVD+RW, and there'd been absolutely no software or hardware changes 
since the previous successful run.

Although I don't think upgrading the ports is responsible I've tried 
downgrading k3b from 1.0.4_1 to 1.0.4 but that had no effect, nor did 
downgrading dvd+rw-tools-7.1 to 7.0. I don't think any of the other 
upgraded ports would have been significant.

Turning off DMA by setting hw.ata.ata_dma and hw.ata.atapi_dma to zero 
stops the errors but with a big performance hit so that's not an option 
for a permanent fix.

I've now run out of ideas for what to try next so any suggestions would 
be welcome.

-- 
Mike Clarke


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