Messages in this thread | | | Date | Fri, 2 Aug 2013 08:13:40 -0400 | From | Konrad Rzeszutek Wilk <> | Subject | Re: [PATCH RFC 1/8] arm: make SWIOTLB available |
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On Fri, Aug 02, 2013 at 12:59:00PM +0100, Stefano Stabellini wrote: > On Wed, 31 Jul 2013, Konrad Rzeszutek Wilk wrote: > > Stefano Stabellini <stefano.stabellini@eu.citrix.com> wrote: > > >Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > > >CC: will.deacon@arm.com > > >CC: linux@arm.linux.org.uk > > >--- > > > arch/arm/Kconfig | 7 +++++++ > > > arch/arm/include/asm/dma-mapping.h | 24 ++++++++++++++++++++++++ > > > 2 files changed, 31 insertions(+), 0 deletions(-) > > > > > >diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > > >index ba412e0..05125ab 100644 > > >--- a/arch/arm/Kconfig > > >+++ b/arch/arm/Kconfig > > >@@ -1832,6 +1832,13 @@ config CC_STACKPROTECTOR > > > neutralized via a kernel panic. > > > This feature requires gcc version 4.2 or above. > > > > > >+config SWIOTLB > > >+ def_bool y > > >+ select NEED_SG_DMA_LENGTH > > >+ > > >+config IOMMU_HELPER > > >+ def_bool SWIOTLB > > >+ > > > > Could you explain the purpose of these two a bit more please? > > SWIOTLB is not available on arm at the moment. > We need to make it available, otherwise SWIOTLB_XEN won't be able to > select it. > > Similarly, IOMMU_HELPER is another lib Kconfig symbol needed by SWIOTLB > to compile.
I was more curious about the NEED_SG_DMA_LENGTH and IOMMU_HELPER. I think the NEED_SG_DMA_LENGTH is optional? Or does SWIOTLB complain about? I do recall seeing a patch for this at some point but it was malformed. It was just changing SWIOTLB to use a macro for sg->dma_length or such.
But the IOMMU_HELPER? That seems odds as the DMA API (which as you know is what SWIOTLB hooks up to) is _below_ the IOMMU API. Ah, it is 'iommu_is_span_boundary' function. Gotcha.
Could you mention that in the git commit please? Just say that SWIOTLB uses some of the common code that IOMMU API uses - which is in the lib/iommu_helper.c hence the need for that.
And for the NEED_SG_DMA_LENGTH let me dig up the patch at some point and send it your way so you can make it part of this series.
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