Re: Missing cache flush.

David Woodhouse (dwmw2@infradead.org)
Tue, 05 Jun 2001 00:29:22 +0100

jgarzik@mandrakesoft.com said:
> > I was pointed at Documentation/DMA-mapping.txt but that doesn't seem
> > very helpful - it's very PCI-specific, and a quick perusal of
> > pci_dma_sync() on i386 shows that it doesn't do what's required anyway.

> What should it do on i386? mb()?

For it to have any use in the situation I described, it would need to
writeback and invalidate the dcache for the affected range. It doesn't seem
to do so, so it seems that it isn't what I require.

The situation is simple - I have a paged RAM setup and I need it cached.
All I want to do is flush and invalidate the cache when I'm about to waggle
whatever I/O ports I waggle to change pages.

There are other situations in which I need the cache flushed, but the above
is one of the simplest.

Even flush_page_to_ram() doesn't seem to do what its name implies, on most
architectures.

--
dwmw2




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