Re: Question about DMA and cd burning.

[jpiszcz <jpiszcz@lucidpixels.com>]

Yes, hdparm -d1 /dev/hd{b,c} did not work on older kernels for me, but 
2.4.20 appears to work successfully.

However, second question, both of my Plextors support UDMA2, and both 
are on 80 PIN/IDE cables, when I enabled -d1 -X66, the kernel, it 
crashed the kernel.

Feb 26 10:30:55 war kernel: hdc: drive_cmd: status=0x41 { DriveReady Error }
Feb 26 10:30:55 war kernel: hdc: drive_cmd: error=0x04
Feb 26 10:30:59 war kernel: hdc: drive_cmd: status=0x41 { DriveReady Error }
Feb 26 10:30:59 war kernel: hdc: drive_cmd: error=0x04
Feb 26 10:31:02 war kernel: hdc: drive_cmd: status=0x41 { DriveReady Error }
Feb 26 10:31:02 war kernel: hdc: drive_cmd: error=0x04
Feb 26 10:32:22 war kernel: scsi : aborting command due to timeout : pid 
11206, scsi1, channel 0, id 1, lun 0 Read (10) 00 00 00 00 00 00 00 02 00
Feb 26 10:32:22 war kernel: hdc: timeout waiting for DMA
Feb 26 10:32:22 war kernel: ide_dmaproc: chipset supported 
ide_dma_timeout func only: 14
Feb 26 10:32:22 war kernel: hdc: status timeout: status=0xd8 { Busy }
Feb 26 10:32:22 war kernel: hdc: drive not ready for command

After this, X froze and the keyboard lights were blinking, I could not 
change to console or anything to see the kernel messages.

1] Why does the kernel turn DMA off by default?
     config: http://installkernel.tripod.com/config-2.4.20.txt
2] Why does the kernel crash when I try to enable UDMA2 on the cdrw?


vishwas@india.hp.com wrote:

> use: hdparam -d1 /dev/<hdX>
>
> to enable DMA, if it still says it cannot enable DMA.
> try enabling the xfermode,which gives me the same
> performace as DMA enabled.
>
> hdparam -X<num> /dev/<hdX>
>     put num greater than 32..like 33,34 etc  (for multiword DMA)
>     OR  greater that 64....like 65 66 etc.   (for UltraDMA)
>
> -vvp
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