linux-kernel - Re: [PATCH 1/7] x86: add alloc_coherent dma

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Date:	Wed, 13 Aug 2008 14:46:36 +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 1/7] x86: add alloc_coherent dma_ops callback to GART driver

On Wed, Aug 13, 2008 at 09:45:54AM +0900, FUJITA Tomonori wrote:
> On Tue, 12 Aug 2008 17:24:11 +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 cdab678..55cc388 100644
> > --- a/arch/x86/kernel/pci-gart_64.c
> > +++ b/arch/x86/kernel/pci-gart_64.c
> > @@ -499,6 +499,26 @@ 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;
> > +
> > +	free_pages((unsigned long)vaddr, get_order(size));
> > +
> > +	return NULL;
> > +}
> > +
> >  static int no_agp;
> 
> It would be better to return a size-aligned memory as DMA-mapping.txt
> says (though I don't think that it doesn't matter much):
> 
> http://lkml.org/lkml/2008/8/8/555

Agreed. I try to change the patchset so it returns size aligned dma
addresses.
 
> I also think that x86 IOMMUs need to handle DMA_*BIT_MASK properly,
> don't we?

Shouldn't this be done by the IOMMUs using your iommu_area_alloc()
function? Or do I misunderstand something?

Joerg

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