Messages in this thread | | | Date | Sun, 09 Jun 2002 21:24:22 -0700 (PDT) | Subject | Re: PCI DMA to small buffers on cache-incoherent arch | From | "David S. Miller" <> |
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From: Oliver Neukum <Oliver.Neukum@lrz.uni-muenchen.de> Date: Sun, 9 Jun 2002 08:45:49 +0200
Am Sonntag, 9. Juni 2002 07:29 schrieb David S. Miller: > From: Roland Dreier <roland@topspin.com> > Date: 08 Jun 2002 18:26:12 -0700 > > Just to make sure I'm reading this correctly, you're saying that as > long as a buffer is OK for DMA, it should be OK to use a > sub-cache-line chunk as a DMA buffer via pci_map_single(), and > accessing the rest of the cache line should be OK at any time before, > during and after the DMA. > > Yes. Does this mean that this piece of memory does have to be declared uncacheable until DMA is finished ? How else do you solve th problem of validity during DMA and especially after DMA ?
You flush either before/after depending upon whether the cpu caches are writeback in nature or not, and the cpu is not allowed to touch those addresses while the device is doing the DMA. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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