linux-kernel - Re: [PATCH 1/8] x86: add alloc_coherent dma

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Message-ID: <20080821151724.GB3189@amd.com>
Date:	Thu, 21 Aug 2008 17:17:24 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
CC:	mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
	linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
	muli@...ibm.com
Subject: Re: [PATCH 1/8] x86: add alloc_coherent dma_ops callback to GART driver

On Thu, Aug 21, 2008 at 11:16:49PM +0900, FUJITA Tomonori wrote:
> On Tue, 19 Aug 2008 16:32:39 +0200
> Joerg Roedel <joerg.roedel@....com> wrote:
> 
> > Signed-off-by: Joerg Roedel <joerg.roedel@....com>
> > ---
> >  arch/x86/kernel/pci-gart_64.c |   21 +++++++++++++++++++++
> >  1 files changed, 21 insertions(+), 0 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
> > index 4d8efb0..44a75a6 100644
> > --- a/arch/x86/kernel/pci-gart_64.c
> > +++ b/arch/x86/kernel/pci-gart_64.c
> > @@ -506,6 +506,26 @@ error:
> >  	return 0;
> >  }
> >  
> > +/* allocate and map a coherent mapping */
> > +static void *
> > +gart_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_addr,
> > +		    gfp_t flag)
> > +{
> > +	void *vaddr;
> > +
> > +	vaddr = (void *)__get_free_pages(flag, get_order(size));
> > +	if (!vaddr)
> > +		return NULL;
> > +
> > +	*dma_addr = gart_map_single(dev, __pa(vaddr), size, DMA_BIDIRECTIONAL);
> > +	if (*dma_addr != bad_dma_address)
> > +		return vaddr;
> 
> I'm not sure a rule is documented or not, but I think that IOMMUs
> return zeroed memory wrt dma_alloc_coherent. The current pci-dma.c
> does, so I think that it would be better to keep the current behavior.

Ok, true. I will send and update patch to add this. Thanks.

Joerg

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