On Fri, Feb 17, 2023 at 12:08:42PM +0100, Marek Szyprowski wrote: > Hi, > > I'm sorry for a delay in replying, but I was busy with other stuff. > > On 23.01.2023 22:00, Jason Gunthorpe wrote: > > On Mon, Jan 23, 2023 at 10:31:01AM +0100, Marek Szyprowski wrote: > >> Add set_platform_dma_ops() required for proper driver operation on ARM > >> 32bit arch after recent changes in the IOMMU framework (detach ops > >> removal). > > Thanks for looking into this! > > > > Can you explain more about how this actually solves the problem in the > > commit message? I don't get it. > > Exynos DRM driver calls arm_iommu_detach_device(), then > arm_iommu_attach_device() with a difrent 'mapping', see > drivers/gpu/drm/exynos/exynos_drm_dma.c Lack of set_platform_dma_ops > leads to a warning in iommu_group_do_set_platform_dma(). The other case > of calling arm_iommu_detach_device() is after unsuccessful probe of the > platform device. Why can't this just use the normal iommu path in all cases? It looks like it is trying to copy the DMA API domain from a parent device to a sub device. Even when using arm_iommu an iommu_domain is still present, so the copy code should work? Though I'm still not really sure how this arm_iommu stuff works.. eg if a driver does iommu_device_claim_dma_owner() how does the iommu_domain get set back to the arm_iommu's mapping's iommu_domain? According to the API that is what set_platform is supposed to do (eg it is what s390 does), but I don't see any code like that in any of the ARM32 drivers.. Jason
