drm/rockchip: Set VOP for the DRM DMA device

Use VOP for DMA operations performed by DRM core. Rockchip DRM driver
is backed by a virtual device that isn't IOMMU-capable, while VOP is the
actual display controller device backed by IOMMU. Fixes "swiotlb buffer
is full" warning messages originated from GEM prime code paths.

Note, that backporting is non-trivial as this depends on
commit 143ec8d3f9396 ("drm/prime: Support dedicated DMA device for dma-buf
imports"), which landed in v6.16 and commit 421be3ee36a4 ("drm/rockchip:
Refactor IOMMU initialisation"), which landed in v5.19.

Reported-by: Daniel Stone <daniels@collabora.com>
Fixes: 2048e3286f34 ("drm: rockchip: Add basic drm driver")
Cc: stable@vger.kernel.org # v6.16+
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Tested-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20251022161948.199731-1-dmitry.osipenko@collabora.com

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index c5c6e2b5772d8ae838453a3081d59942fc99bff0..3099408e9d0505a7fbeec14ca2dc84441fbe603a 100644 (file)
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -97,6 +97,9 @@ void rockchip_drm_dma_init_device(struct drm_device *drm_dev,
                private->iommu_dev = ERR_PTR(-ENODEV);
        else if (!private->iommu_dev)
                private->iommu_dev = dev;
+
+       if (!IS_ERR(private->iommu_dev))
+               drm_dev_set_dma_dev(drm_dev, private->iommu_dev);
 }
 
 static int rockchip_drm_init_iommu(struct drm_device *drm_dev)