Re: [PATCH -tip 1/3] IA64: fix swiotlb alloc_coherent for non

FUJITA Tomonori
2009-01-29T23:36:12Z

On Fri, 30 Jan 2009 07:54:07 +0900
Yasunori Goto <y-goto@jp.fujitsu.com> wrote:

> > On Thu, 29 Jan 2009 20:41:07 +0900
> > Yasunori Goto <y-goto@jp.fujitsu.com> wrote:
> >
> > > > Before the dma ops unification, IA64 always uses GFP_DMA for
> > > > dma_alloc_coherent like:
> > > >
> > > > #define dma_alloc_coherent(dev, size, handle, gfp) \
> > > > platform_dma_alloc_coherent(dev, size, handle, (gfp) | GFP_DMA)
> > > >
> > > > This GFP_DMA enforcement doesn't make sense for IOMMUs since they can
> > > > do address translation to give addresses that devices can access
> > > > to. The IOMMU drivers ignore the zone flag. However, this is still
> > > > necessary for swiotlb since it can't do address translation.
> > > >
> > > > We don't always need to use GFP_DMA for swiotlb. We need GFP_DMA for
> > > > devices incapable of 64bit DMA.
> > > >
> > > > This patch is sorta updated version of:
> > > >
> > > > http://marc.info/?l=linux-kernel&m\x122638215612705&w=2
> > > >
> > > > Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> > > > Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
> > > > ---
> > > > arch/ia64/kernel/pci-swiotlb.c | 10 +++++++++-
> > > > 1 files changed, 9 insertions(+), 1 deletions(-)
> > > >
> > > > diff --git a/arch/ia64/kernel/pci-swiotlb.c b/arch/ia64/kernel/pci-swiotlb.c
> > > > index 717ad4f..573f02c 100644
> > > > --- a/arch/ia64/kernel/pci-swiotlb.c
> > > > +++ b/arch/ia64/kernel/pci-swiotlb.c
> > > > @@ -13,8 +13,16 @@
> > > > int swiotlb __read_mostly;
> > > > EXPORT_SYMBOL(swiotlb);
> > > >
> > > > +static void *ia64_swiotlb_alloc_coherent(struct device *dev, size_t size,
> > > > + dma_addr_t *dma_handle, gfp_t gfp)
> > > > +{
> > > > + if (dev->coherent_dma_mask != DMA_64BIT_MASK)
> > > > + gfp |= GFP_DMA;
> > > > + return swiotlb_alloc_coherent(dev, size, dma_handle, gfp);
> > > > +}
> > > > +
> > > > struct dma_map_ops swiotlb_dma_ops = {
> > > > - .alloc_coherent = swiotlb_alloc_coherent,
> > > > + .alloc_coherent = ia64_swiotlb_alloc_coherent,
> > > > .free_coherent = swiotlb_free_coherent,
> > > > .map_page = swiotlb_map_page,
> > > > .unmap_page = swiotlb_unmap_page,
> > > > --
> > > > 1.6.0.6
> > >
> > >
> > > Though I may be misunderstanding something, this initialization seems to be
> > > called only when CONFIG_IA64_DIG_VTD is on.
> >
> > Hmm, what's 'this initialization'?
> >
> > This patch always sets swiotlb_dma_ops.alloc_coherent to
> > ia64_swiotlb_alloc_coherent.
>
> I tested your patch, but, ia64_swiotlb_alloc_coherent() was not called with
> CONFIG_GENERIC.

You use the generic kernel on a DIG box, right? If so, yeah, there is
something wrong.

> swiotlb_dma_ops is set by pci_swiotlb_init().
> However, it seems to be not called when CONFIG_IA64_DIG/Generic configuration.

You are talking about setting dma_ops to swiotlb_dma_ops?

I think that swiotlb_dma_init() also sets dma_ops to swiotlb_dma_ops.