Messages in this thread | | | Date | Mon, 13 Jan 2003 10:49:49 -0800 | From | Ross Biro <> | Subject | Re: Linux 2.4.21-pre3-ac4 |
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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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