Hi Inki/Marek, On Tue, 16 Oct 2012 02:50:16 +0200 Inki Dae <inki....@samsung.com> wrote:
> 2012/10/15 Marek Szyprowski <m.szyprow...@samsung.com>: > > Hello, > > > > Some devices, which have IOMMU, for some use cases might require to > > allocate a buffers for DMA which is contiguous in physical memory. Such > > use cases appears for example in DRM subsystem when one wants to improve > > performance or use secure buffer protection. > > > > I would like to ask if adding a new attribute, as proposed in this RFC > > is a good idea? I feel that it might be an attribute just for a single > > driver, but I would like to know your opinion. Should we look for other > > solution? > > > > In addition, currently we have worked dma-mapping-based iommu support > for exynos drm driver with this patch set so this patch set has been > tested with iommu enabled exynos drm driver and worked fine. actually, > this feature is needed for secure mode such as TrustZone. in case of > Exynos SoC, memory region for secure mode should be physically > contiguous and also maybe OMAP but now dma-mapping framework doesn't > guarantee physically continuous memory allocation so this patch set > would make it possible. Agree that the contigous memory allocation is necessary for us too. In addition to those contiguous/discontiguous page allocation, is there any way to _import_ anonymous pages allocated by a process to be used in dma-mapping API later? I'm considering the following scenario, an user process allocates a buffer by malloc() in advance, and then it asks some driver to convert that buffer into IOMMU'able/DMA'able ones later. In this case, pages are discouguous and even they may not be yet allocated at malloc()/mmap(). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
