Re: DMA transfers in 2.5.67

Måns Rullgård (mru@users.sourceforge.net)
15 Apr 2003 23:38:14 +0200


Alan Cox <alan@lxorguk.ukuu.org.uk> writes:

> > What do I need to do in a driver before doing DMA transfers to a PCI
> > card? Using a driver that worked in 2.4 gives a throughput of only 10
> > MB/s in 2.5.67. Is there some magic initialization that I have
> > missed?
>
> Assuming your driver uses the new PCI api for DMA in 2.4/2.5 then there
> isnt really anything to watch. Is this on a box with > 800Mb of memory
> however ?

It's an Alpha with 768 MB. Is it the pci_alloc_* functions you are
referring to? I don't think they are used currently. How much memory
can these allocate? I need chunks of up to 1 MB, not necessarily
phycically continuous.

What do those functions do that normal memory allocation does not?
Apart from setting up sg mappings, that is.

-- 
Måns Rullgård
mru@users.sf.net
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