[PATCH v1] drm/rockchip: Set VOP for the DRM DMA device

[Dmitry Osipenko <dmitry.osipenko@collabora.com>]

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 143ec8d3f9396
("drm/prime: Support dedicated DMA device for dma-buf imports"), which
landed in v6.16 and 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>
---
 drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index eb77bde9f628..e693160e9b7f 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -96,6 +96,9 @@ 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)
-- 
2.51.0