Here is what happens after several days running with either the kernel activating DMA or activating it manually (hdparm -d1 /dev/hda) in at least 2.4.2 through 2.4.5-ac5: hda: timeout waiting for DMA ide_dmaproc: chipset supported ide_dma_timeout func only: 14 hda: irq timeout: status=0x80 { Busy } hda: DMA disabled ide0: reset: success Issuing hdparm -d1 /dev/hda at this point causes a short period of system unresponsiveness which ends with the following: hda: timeout waiting for DMA ide_dmaproc: chipset supported ide_dma_timeout func only: 14 hda: irq timeout: status=0x50 { DriveReady SeekComplete } hda: timeout waiting for DMA ide_dmaproc: chipset supported ide_dma_timeout func only: 14 hda: irq timeout: status=0x50 { DriveReady SeekComplete } hda: timeout waiting for DMA ide_dmaproc: chipset supported ide_dma_timeout func only: 14 hda: irq timeout: status=0x50 { DriveReady SeekComplete } hda: timeout waiting for DMA ide_dmaproc: chipset supported ide_dma_timeout func only: 14 hda: irq timeout: status=0x50 { DriveReady SeekComplete } hda: DMA disabled ide0: reset: success Here is the drive info: hdparm -iI /dev/hda /dev/hda: Model=IBM-DTTA-371010, FwRev=T77OA73A, SerialNo=WL0WLF36394 Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=34 BuffType=DualPortCache, BuffSize=465kB, MaxMultSect=16, MultSect=off CurCHS=16383/16/63, CurSects=-66060037, LBA=yes, LBAsects=19746720 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 udma0 udma1 *udma2 AdvancedPM=no Drive Supports : ATA/ATAPI-4 T13 1153D revision 17 : ATA-1 ATA-2 ATA-3 ATA-4 Model=BI-MTDAT3-1710 0 , FwRev=7TO77AA3, SerialNo= W 0LLW3F3649 Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=34 BuffType=DualPortCache, BuffSize=465kB, MaxMultSect=16, MultSect=off CurCHS=16383/16/63, CurSects=-66060037, LBA=yes, LBAsects=19746720 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 udma0 udma1 udma2 AdvancedPM=no Drive Supports : ATA/ATAPI-4 T13 1153D revision 17 : ATA-1 ATA-2 ATA-3 ATA-4 Here is the controller info: 00:11.0 Unknown mass storage controller: Promise Technology, Inc. 20262 (rev 01) Subsystem: Promise Technology, Inc.: Unknown device 4d33 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: 64 Interrupt: pin A routed to IRQ 11 Region 0: I/O ports at f4f0 [size=8] Region 1: I/O ports at fc88 [size=4] Region 2: I/O ports at f4f8 [size=8] Region 3: I/O ports at fc8c [size=4] Region 4: I/O ports at fcc0 [size=64] Region 5: Memory at fcfe0000 (32-bit, non-prefetchable) [size=128K] Expansion ROM at <unassigned> [disabled] [size=64K] Capabilities: [58] Power Management version 1 Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-) Status: D0 PME-Enable- DSel=0 DScale=0 PME- I also see this on the onboard controller 00:00.0 Host bridge: Intel Corporation 430VX - 82437VX TVX [Triton VX] (rev 02) 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 00:07.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II] (prog-if 80 [Master]) 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: 64 Region 4: I/O ports at fc90 [size=16] I distinctly remember being able to re-enable DMA after the DMA timeout in 2.2.x. What gives? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/