Re: [RFC] AGP initial support for chipset flushing..
From: Keith Packard
Date: Mon Oct 29 2007 - 16:13:36 EST
On Mon, 2007-10-29 at 12:47 -0700, Jesse Barnes wrote:
> In this case, we're performing basically a dma_sync*(...DMA_TO_DEVICE)
> right?
But this is just for the GPU; every other DMA device in the system is
cache-coherent.
> Can we be sure that a single flush is sufficient? Is there any
> window between when we flush and when we start accessing memory with
> the device that we could get into more caching trouble?
An uncached write to this page will not complete until the buffers are
completely flushed.
> Looks reasonable, I'm not sure we can do much better. The only concern
> I have is that allocating some more PCI space like that may end up
> clobbering some *other* hidden BIOS mapping, but there's not a whole
> lot we can do about that.
This isn't a hidden mapping; the i965 doesn't allocate space for it in
the BIOS.
--
keith.packard@xxxxxxxxx
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