Re: [PATCH V2 2/3] powerpc: Add support for swiotlb on 32-bit

From: Becky Bruce
Date: Wed May 27 2009 - 15:06:13 EST

On May 22, 2009, at 5:51 AM, FUJITA Tomonori wrote:

On Thu, 21 May 2009 13:18:54 -0700
Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:

Becky Bruce wrote:
I can work with that, but it's going to be a bit inefficient, as I
actually need the dma_addr_t, not the phys_addr_t, so I'll have to
convert. In every case, this is a conversion I've already done and
that I need in the calling code as well. Can we pass in both the
phys_addr_t and the dma_addr_t?

The Xen implementation would needs to do the phys to bus conversion page
by page anyway, so it wouldn't help much. But it also wouldn't hurt.

How expensive is the phys-to-bus conversion on power? Is it worth
making the interface more complex for? Would passing phys+bus mean that
we wouldn't also need to pass dev?

I don't think so. POWERPC needs it.

Hrm, it looks like my response to this got dropped. Fujita is correct - we still need the dev on powerpc because we use it to get device- specific information that is used to determining when we need to actually bounce.


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