Re-enabling DMA in CD driver.

Dave Jones. (djones2@glam.ac.uk)
Thu, 1 Apr 1999 10:56:46 +0000 ( )


Last night I inserted a CD, mounted it, and got this in the logs.

Mar 31 23:22:25 nemesis kernel: hdc: irq timeout: status=0xd0 { Busy }
Mar 31 23:22:25 nemesis kernel: hdc: DMA disabled
Mar 31 23:22:25 nemesis kernel: hdc: ATAPI reset complete

After this, the CD mounted with no problem.

Normally, my CD drive works in DMA mode, it was a one off with this one
CD. When I put a CD in, the drive light comes on, there's some activity,
then it goes off. At this point it is safe to mount. I think I may have
tried to mount it before the drive had recognised there was a CD inserted.

The problem is, that it never gets turned back on. I had to run hdparm to
switch it back on, and if I hadn't been dumping the logs to a spare tty,
I'd not have realised it was off. Maybe DMA should be re-enabled on
insertion of a new CD? But only if 'DMA by default' is enabled.
Otherwise, people with CDROMs that don't support DMA xfers would get
'enabled' and then 'disabled' with each CD they insert.

Thoughts & opinions ?

regards,

Dave.

_____________________________________________________________
| Dave 'Barc0de' Jones. (barc0de@digital-corruption.net) |
| http://www.comp.glam.ac.uk/students/djones2/ |
|_____________________________________________________________|

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/