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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
time.

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

Ross


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