non aligned DMA transfer attempted

[Ryan Rogers]

Alexander Motin wrote:
> Ryan Rogers wrote:
>> I'm having a bit of a problem getting my DVD drive(s) to work 
>> correctly.   I'm trying to transfer my DVD collection to my media 
>> server, but whenever I run vobcopy, /var/log/messages gets spammed with:
>>
>> acd0: FAILURE - non aligned DMA transfer attempted
>> acd0: setting up DMA failed
>>
>> I added a bit more information to the first message to see if I could 
>> figure out what was actually going on.  request->data was 0xd40e0c37, 
>> ch->dma.alignment was 2, and request->bytecount was 2048.
> 
> Actually I don't understand what for this check was made there. It is 
> busdma infrastructure business to implement buffer bouncing to manage 
> requested alignment. But this check enforces application level to bother 
> with this. Usually it works fine, as memory often allocated aligned. But 
> probably here is some specifics in your application. Could you try to 
> just to comment-out that request->data check?
> 

I commented out that part of the check, and it worked in the sense that 
it didn't spit out any errors at me, but I'm not 100% certain that the 
data isn't getting corrupted.  I tried ripping two discs.  The first is 
completely corrupted, the second appears to be fine on first glance. 
I'm going to try a couple more discs to see if maybe the first one was 
just bad.

Also, one other thing that I noticed that seems odd is this:

acd0: DVDR <TSSTcorp CDDVDW SH-S223L/SB02> at ata6-master SATA150
....
cd0: <TSSTcorp CDDVDW SH-S223L SB02> Removable CD-ROM SCSI-0 device
cd0: 3.300MB/s transfers

I timed how long the first disc took to rip, and it seems to match that 
reported speed.  "Working but slow" is certainly better than "not 
working", but my speeds in Windows using DVD Decrypter on the same disk 
are at least 3 times faster, bursting up to about 5 times faster.

Ryan