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SubjectRe: Linux 2.4.21-pre3-ac4
Benjamin Herrenschmidt wrote:

>On Sun, 2003-01-12 at 21:27, Alan Cox wrote:
>>which currently has two problems Ross found
>>1. The processors or so fast we have to enforce the 400nS delay nowdays\

The reason we need to enforce the 400nS delay is because of what is
going on on the other processor. If the other processor is in ide_intr
trying to grab the spinlock and we do not give the drive time to assert
the busy bit and the other processor makes it to the call to
drive_is_ready, then the drive could still return not busy and we could
think the command is done. This code path is probably less than 50
instructions, so I don't think it's taken anywhere near 400ns for a long

DMA is slightly different. We don't actually have to delay the 400ns if
we call ide_dma_begin from inside the spinlock.


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