Messages in this thread | | | Subject | Re: [CFT] Bus mastering support for IDE CDROM audio | From | Ed Sweetman <> | Date | 28 Jan 2002 10:50:01 -0500 |
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I've always been able to get it back to dma for packet by forcing the drive to sleep mode and then letting the kernel wake it. I guess I'll try this 3rd version patch when I get back from class today and see if that still works.
hdparm -Y /dev/cdrom
then go and set dma again with hdparm.
Although this could just be fickleness of my cdrom.
On Mon, 2002-01-28 at 04:51, Andrew Morton wrote: > benh@kernel.crashing.org wrote: > > > > >At no stage does a packet-mode DMA error turn off drive-level > > >DMA. This is because some devices seem to perform ordinary > > >ATA DMA OK, but screw up packet DMA. > > > > > >The kernel internally retries the requests when it performs fallback, > > >so userspace shouldn't see any disruption as the kernel works > > >out what to do. > > > > > >Once the drive has fallen back to single-frame (or PIO mode) for > > >packet reads, the only way to get it back to a higher level is > > >a reboot. > > > > Doesn that mean that a bad media (typically a scratched CDROM) will > > cause the drive to revert to PIO until next reboot ? > > > > Nope. This error handling is specifically for busmastering > errors, not for media errors. > > I've tested media errors (whiteboard marker scribblings on the > CD do this nicely). DMA errors (bad return value from > HWIF->dmaproc) I can only simulate. > > > -
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