01.10.2013, 18:16, "Konrad Rzeszutek Wilk" <konrad.wilk@xxxxxxxxxx>: > On Tue, Oct 01, 2013 at 12:16:16PM +0200, Thomas Hellstrom wrote: > >> Jerome, Konrad >> >> Forgive an ignorant question, but it appears like both Nouveau and >> Radeon may use pci_map_page() when populating TTMs on >> pages obtained using the ordinary (not DMA pool). These pages will, >> if I understand things correctly, not be pages allocated with >> DMA_ALLOC_COHERENT. > > Not always. That depends if the SWIOTLB buffer has been enabled. > Which happens if you have Calgary IOMMU, AMD GART and if you > run under Xen. > >> From what I understand, at least for the corresponding >> dma_map_page() it's illegal for the CPU to access these pages >> without calling >> dma_sync_xx_for_cpu(). And before the device is allowed to access >> them again, you need to call dma_sync_xx_for_device(). > > Correct. > >> So mapping for PCI really invalidates the TTM interleaved CPU / >> device access model. > > Unless you use the TTM DMA one which allocates them from the > coherent pool - in which case they are already mapped. > > Granted the part of using DMA export/import API is not finished > (so moving from TTM pool to a V4L for example) and it will blow > up with the right mix. > >> Or did I miss something here? > > That is it. But for most of the use cases the drivers have been > able to skirt this restriction b/c the pci_map_page/pci_unmap_page > setup a DMA mapping that is static (until the pci_unmap_page) and > on x86 the memory is coherent. So the map is good irregardless > of the PCI devices. Naturally if you have multitple IOMMUs per bridge > this all falls apart :-( > > This all falls flat also with non-coherent memory and I believe > that is what some of the PA-RISC folks are hitting their heads > against. Konrad, As i already answered you, this is irrelevant to the 2.0 version of PA-RISC architecture on which we run our ATI video options. > > And probably also on ARM once they start using these chipsets. > >> Thanks, >> Thomas > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > http://lists.freedesktop.org/mailman/listinfo/dri-devel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
