On Thu, Sep 18, 2014 at 02:17:33PM +0300, Laurent Pinchart wrote:
> Hi Will,
>
> Thank you for the patch.
>
> On Friday 12 September 2014 17:34:53 Will Deacon wrote:
> > This patch extends of_dma_configure so that it sets up the IOMMU for a
> > device, as well as the coherent/non-coherent DMA mapping ops.
> >
> > Signed-off-by: Will Deacon <will.dea...@arm.com>
> > ---
> > arch/arm/include/asm/dma-mapping.h | 4 +++-
> > drivers/of/platform.c | 24 +++++++++++++++++-------
> > include/linux/dma-mapping.h | 8 +++++++-
> > 3 files changed, 27 insertions(+), 9 deletions(-)
> >
> > diff --git a/arch/arm/include/asm/dma-mapping.h
> > b/arch/arm/include/asm/dma-mapping.h index 7e9ac4f604c3..a8bb0c494bb3
> > 100644
> > --- a/arch/arm/include/asm/dma-mapping.h
> > +++ b/arch/arm/include/asm/dma-mapping.h
> > @@ -121,7 +121,9 @@ static inline unsigned long dma_max_pfn(struct device
> > *dev) }
> > #define dma_max_pfn(dev) dma_max_pfn(dev)
> >
> > -static inline void arch_setup_dma_ops(struct device *dev, bool coherent)
> > +static inline void arch_setup_dma_ops(struct device *dev, u64 dma_base,
> > + u64 size, struct iommu_dma_mapping *iommu,
> > + bool coherent)
> > {
> > if (coherent)
> > set_dma_ops(dev, &arm_coherent_dma_ops);
> > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > index 946dd7ae0394..95ebd38db545 100644
> > --- a/drivers/of/platform.c
> > +++ b/drivers/of/platform.c
> > @@ -19,6 +19,7 @@
> > #include <linux/slab.h>
> > #include <linux/of_address.h>
> > #include <linux/of_device.h>
> > +#include <linux/of_iommu.h>
> > #include <linux/of_irq.h>
> > #include <linux/of_platform.h>
> > #include <linux/platform_device.h>
> > @@ -166,6 +167,7 @@ static void of_dma_configure(struct platform_device
> > *pdev) int ret;
> > bool coherent;
> > unsigned long offset;
> > + struct iommu_dma_mapping *iommu;
> > struct device *dev = &pdev->dev;
> >
> > /*
> > @@ -195,7 +197,19 @@ static void of_dma_configure(struct platform_device
> > *pdev) dev_dbg(dev, "device is%sdma coherent\n",
> > coherent ? " " : " not ");
> >
> > - arch_setup_dma_ops(dev, coherent);
> > + iommu = of_iommu_configure(dev);
> > + dev_dbg(dev, "device is%sbehind an iommu\n",
> > + iommu ? " " : " not ");
> > +
> > + arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent);
> > +
> > + if (iommu)
> > + kref_put(&iommu->kref, of_iommu_deconfigure);
>
> What's the expected life cycle of the iommu_dma_mapping structure ? It gets
> created by of_iommu_configure() and the initial reference gets dropped here.
> I
> suppose you expect arch code to need to keep a reference to the structure,
> but
> your implementation in patch 7/7 doesn't. As far as I can see, you don't even
> use the contents of the structure in the ARM arch_setup_dma_ops()
> implementation. Do you expect that to change later, or other architectures to
> need it ?
>
> By the way, now that I think about it, I find struct iommu_dma_mapping and
> struct dma_iommu_mapping very confusing.Agreed. I wonder how useful it is to know the set of IOMMU instances that each device can master through. Wouldn't it be more useful to keep a list of master interfaces for each device? The set of IOMMU instances can trivially be derived from that. Thierry
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