No automatic DMA with VIA chipset + CDROM on recent kernels

From: Roy Sigurd Karlsbakk (
Date: Wed Dec 11 2002 - 03:50:06 EST


With the VIA IDE chipset listed below, DMA is off by default on my DVD-ROM and
CD burner attached to the secondary channel (as hd[cd]) on recent kernels.
DMA works fine after an "echo using_dma:1 > /proc/ide/hd[cd]/settings

The .config is attached. This has been tested up to 2.4.20-rc1. I haven't
tried .20 final, as I couldn't find anything related in the changelog.


(from lspci -vvvvv)
00:11.1 IDE interface: VIA Technologies, Inc. Bus Master IDE (rev 06) (prog-if
8a [Master SecP PriP])
        Subsystem: Asustek Computer, Inc.: Unknown device 808c
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B-
        Status: Cap+ 66Mhz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort-
<TAbort- <MAbort- >SERR- <PERR-
        Latency: 32
        Interrupt: pin A routed to IRQ 0
        Region 4: I/O ports at 8000 [size=16]
        Capabilities: [c0] Power Management version 2
                Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA
                Status: D0 PME-Enable- DSel=0 DScale=0 PME-

Roy Sigurd Karlsbakk, Datavaktmester
ProntoTV AS -
Tel: +47 9801 3356

Computers are like air conditioners. They stop working when you open Windows.

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