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SubjectRe: Safety of IRQ during i/o
On 25 Jul 2002, Alan Cox wrote:

> There are also some older systems where if the block transfer of the IDE
> data didn't keep up with the controller instead of handshaking properly
> it kind of dribbled random numbers onto the disk.
>
> Unless anyone knows of PCI era devices with this problem I would be
> inclined to agree that we should default to IRQ unmasking in the 2.5 IDE
> code if the IDE controller is PCI.

Certainly if the controller is running in DMA mode. If running in PIO mode
I would think you could still have a problem if the transfer was stopped
mid-block. Perhaps I'm paranoid, is that a "can't happen" now?

> For old ISA/VLB controllers its safer left as is, and nobody running a
> machine like that can realistically expect good performance without hand
> tuning stuff anyway

I would think the guts of PIO block transfer would have to be protected
anyway, but that's a very small part of the code.

--
bill davidsen <davidsen@tmr.com>
CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

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