Hello, This patch series fixes the rcar-du-drm driver to support VSP plane sources with an IOMMU. It is available for convenience at git://linuxtv.org/pinchartl/media.git iommu/devel/du On R-Car Gen3 the DU has no direct memory access but sources planes through VSP instances. When an IOMMU is inserted between the VSP and memory, the DU framebuffers need to be DMA mapped using the VSP device, not the DU device as currently done. The same situation can also be reproduced on Gen2 hardware by linking the VSP to the DU in DT [1], effectively disabling direct memory access by the DU. The situation is made quite complex by the fact that different planes can be connected to different DU instances, and thus served by different IOMMUs (or, in practice on existing hardware, by the same IOMMU but through different micro-TLBs). We thus can't allocate and map buffers to the right device in a single dma_alloc_wc() operation as done in the DRM CMA GEM helpers. However, on such setups, the DU DT node doesn't reference IOMMUs as the DU does not perform any direct memory access. We can thus keep the GEM object allocation unchanged, and the DMA addresses that we receive in the DU driver will be physical addresses. Those buffers then need to be mapped to the VSP device when they are associated with planes. Fortunately the atomic framework provides two plane helper operations, .prepare_fb() and .cleanup_fb() that we can use for this purpose. The reality is slightly more complex than this on Gen3, as an FCP device instance sits between VSP instances and memory. It is the FCP devices that are connected to the IOMMUs, and buffer mapping thus need to be performed using the FCP devices. This isn't required on Gen2 as the platforms don't have any FCPs. Patches 1/6 and 2/6 unconstify the state argument to the .prepare_fb() and .cleanup_fb() operations, to allow storing the mapped buffer addresses in the state. Patches 3/6 and 4/6 then extend the rcar-fcp driver API to expose the FCP struct device. Patch 5/6 extends the vsp1 driver API to allow mapping a scatter-gather list to the VSP, with the implementation using the FCP devices instead when available. Patch 6/6 then use the vsp1 mapping API in the rcar-du-drm driver to map and unmap buffers when needed. The series has been tested on Gen2 (Lager) only as the Gen3 IOMMU is known to be broken. A possible improvement is to modify the GEM object allocation mechanism to use non-contiguous memory when the DU driver detects that all the VSP instances it is connected to use an IOMMU (possibly through FCP devices). An issue has been noticed with synchronization between page flip and VSP operation. Buffers get unmapped (and possibly freed) before the VSP is done reading them. The problem isn't new, but is much more noticeable with IOMMU support enabled as any hardware access to unmapped memory generates an IOMMU page fault immediately. The series unfortunately contain a dependency between DRM and V4L2 patches, complicating upstream merge. As there's no urgency to merge patch 6/6 due to the IOMMU being broken on Gen3 at the moment, I propose merging patches 1/6-2/6 and 3/6-5/6 independently for the next kernel release. I would particularly appreciate feedback on the APIs introduced by patches 4/6 and 5/6. [1] https://www.mail-archive.com/linux-renesas-soc@xxxxxxxxxxxxxxx/msg06589.html Laurent Pinchart (6): drm: Don't implement empty prepare_fb()/cleanup_fb() drm: Unconstify state argument to prepare_fb()/cleanup_fb() v4l: rcar-fcp: Don't get/put module reference v4l: rcar-fcp: Add an API to retrieve the FCP device v4l: vsp1: Add API to map and unmap DRM buffers through the VSP drm: rcar-du: Map memory through the VSP device drivers/gpu/drm/arc/arcpgu_crtc.c | 2 - drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c | 4 +- drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_plane.c | 15 ----- drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c | 15 ----- drivers/gpu/drm/i915/intel_display.c | 4 +- drivers/gpu/drm/i915/intel_drv.h | 4 +- drivers/gpu/drm/msm/mdp/mdp4/mdp4_plane.c | 4 +- drivers/gpu/drm/msm/mdp/mdp5/mdp5_plane.c | 4 +- drivers/gpu/drm/omapdrm/omap_plane.c | 4 +- drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 74 +++++++++++++++++++++++-- drivers/gpu/drm/rcar-du/rcar_du_vsp.h | 2 + drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 4 +- drivers/gpu/drm/tegra/dc.c | 17 ------ drivers/gpu/drm/vc4/vc4_plane.c | 2 - drivers/media/platform/rcar-fcp.c | 17 +++--- drivers/media/platform/vsp1/vsp1_drm.c | 24 ++++++++ include/drm/drm_modeset_helper_vtables.h | 4 +- include/media/rcar-fcp.h | 5 ++ include/media/vsp1.h | 3 + 19 files changed, 126 insertions(+), 82 deletions(-) -- Regards, Laurent Pinchart _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
