Hi Varun, [adding the Qualcomm guys, as I have an open question below]
On Mon, Oct 06, 2014 at 11:28:15AM +0100, Varun Sethi wrote: > This is used for indicating device memory type for a DMA transaction. IOMMU > driver would set up attributes indicationg access to device memory. > > Signed-off-by: Varun Sethi <varun.se...@freescale.com> > --- > include/linux/iommu.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > index 20f9a52..0599fe1 100644 > --- a/include/linux/iommu.h > +++ b/include/linux/iommu.h > @@ -28,6 +28,7 @@ > #define IOMMU_WRITE (1 << 1) > #define IOMMU_CACHE (1 << 2) /* DMA cache coherency */ > #define IOMMU_EXEC (1 << 3) > +#define IOMMU_DEVICE (1 << 4) /* Indicates access to device memory */ An alternative to this would be to make device-memory the default type for !IOMMU_CACHE mappings (i.e. MAIR index 0). I'd value feedback either way; the argument comes down to whether we should use normal non-cacheable or device-nGnRE as the default (!IOMMU_CACHE) memory type. The latter is likely to be significantly slower, but provides the ordering guarantees that you need for MSI delivery. If we do go down the route of adding a new IOMMU_* option, it probably needs a better name (IOMMU_MMIO, for example). Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
