dvd dma problems

[Dominic Fandrey]

I have a couple of DVD drives (one drive, one burner) that used to play DVDs
quite fine from 5.3 to somewhere in the 6.x branch. Nowadays I have to send
them to PIO4 to play DVDs, because they'll just throw DMA not aligned errors
around in UDMA33 or WDMA2 mode.

Should someone be interested in this I'm willing to supply all necessary
information, such as the exact drives, firmware versions, kernel traces...
whatever comes to your mind. I'm also willing to test patches.