Comment 43 for bug 228624

Bugs bugs bugs. Also having this problem. Hardware is:
https://wiki.ubuntu.com/LaptopTestingTeam/CompaqPresarioV2600CTO

all_generic_ide=1 doesn't fix it. Hardware is fine: works perfectly in windoze.

Possibly related is that my laptop also suffers from this bug: https://bugs.launchpad.net/ubuntu/+bug/175022/
which disables the DMA on my dvd. Curiously, after disabling the workaround in the bug above but enabling all_generic_ide=1 on the kernel command line, the dvd goes back to MWDMA2, which is what I get using the workaround.

various outputs after enabling all_generic_ide=1:

dmesg | grep -i ata
[ 46.054199] libata version 3.00 loaded.
[ 46.055768] scsi0 : ata_generic
[ 46.055876] scsi1 : ata_generic
[ 46.056814] ata1: PATA max UDMA/100 cmd 0x1f0 ctl 0x3f6 bmdma 0x8410 irq 14
[ 46.056861] ata2: PATA max UDMA/100 cmd 0x170 ctl 0x376 bmdma 0x8418 irq 15
[ 46.221624] ata1.00: ATA-6: HTS424040M9AT00, MA2OA72A, max UDMA/100
[ 46.221672] ata1.00: 78140160 sectors, multi 16: LBA
[ 46.221728] ata1.00: configured for UDMA/100
[ 46.540958] ata2.00: ATAPI: MATSHITADVD-RAM UJ-840S, 1.11, max MWDMA2
[ 46.541014] ata2.00: configured for MWDMA2
[ 46.541153] scsi 0:0:0:0: Direct-Access ATA HTS424040M9AT00 MA2O PQ: 0 ANSI: 5

hdparm -i /dev/scd0

/dev/scd0:

 Model=MATSHITADVD-RAM UJ-840S , FwRev=1.11 , SerialNo=
 Config={ Fixed Removeable DTR<=5Mbs DTR>10Mbs nonMagnetic }
 RawCHS=0/0/0, TrkSize=0, SectSize=0, ECCbytes=0
 BuffType=unknown, BuffSize=0kB, MaxMultSect=0
 (maybe): CurCHS=0/0/0, CurSects=0, LBA=yes, LBAsects=0
 IORDY=on/off, tPIO={min:240,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes: pio0 pio1 pio2 pio3 pio4
 DMA modes: sdma0 sdma1 sdma2 mdma0 mdma1 *mdma2
 AdvancedPM=no
 Drive conforms to: Unspecified: ATA/ATAPI-3,4,5,6

 * signifies the current active mode