Messages in this thread | | | From | Benjamin Herrenschmidt <> | Subject | Re: PCI DMA to small buffers on cache-incoherent arch | Date | Tue, 11 Jun 2002 19:29:20 +0200 |
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>This may use less memory than 1) or 2) above on some architectures but >will use more than 1) on cache-coherent architectures. It makes the >code even more complex since now the code that allocates the dma >buffer has to know which PCI device will use it (for example, in USB, >the hub driver is separated from the HCD driver, which is who knows >about the PCI bus).
What about an arch that can be both coherent or incoherent (the same kernel binary would boot both) ?
I can also imagine quite a bunch of embedded stuffs where you may have both coherent and non-coherent devices depending on the bus the live on or on bridge bugs.
For your example, I don't buy it. You could well design the USB urb allocation in such a way that they are passed down the controller of a given device.
Ben.
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