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

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Message-Id: <20090522194930E.fujita.tomonori@lab.ntt.co.jp>
Date:	Fri, 22 May 2009 19:51:46 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	jeremy@...p.org
Cc:	beckyb@...nel.crashing.org, fujita.tomonori@....ntt.co.jp,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	Ian.Campbell@...rix.com
Subject: Re: [PATCH V2 2/3] powerpc: Add support for swiotlb on 32-bit

On Thu, 21 May 2009 13:18:54 -0700
Jeremy Fitzhardinge <jeremy@...p.org> 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.
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