[PATCH] drm/rockchip: Detach from ARM DMA domain in attach_device

[Steven Price]

Since commit 1ea2a07a532b ("iommu: Add DMA ownership management
interfaces") the Rockchip display driver on the Firefly RK3288 fails to
initialise properly. This is because ARM DMA domain is still attached.

Let's follow the lead of exynos and tegra and add code to explicitly
remove the ARM domain before attaching a new one.

Suggested-by: Robin Murphy <robin.murphy at arm.com>
Signed-off-by: Steven Price <steven.price at arm.com>
---
See also the thread[1] where I reported the regression.

[1] https://lore.kernel.org/linux-kernel/da9cca0a-ec5b-2e73-9de0-a930f7d947b2%40arm.com
---
 drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index 67d38f53d3e5..13ed33e74457 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -23,6 +23,14 @@
 #include <drm/drm_probe_helper.h>
 #include <drm/drm_vblank.h>
 
+#if defined(CONFIG_ARM_DMA_USE_IOMMU)
+#include <asm/dma-iommu.h>
+#else
+#define arm_iommu_detach_device(...)	({ })
+#define arm_iommu_release_mapping(...)	({ })
+#define to_dma_iommu_mapping(dev) NULL
+#endif
+
 #include "rockchip_drm_drv.h"
 #include "rockchip_drm_fb.h"
 #include "rockchip_drm_gem.h"
@@ -49,6 +57,15 @@ int rockchip_drm_dma_attach_device(struct drm_device *drm_dev,
 	if (!private->domain)
 		return 0;
 
+	if (IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)) {
+		struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
+
+		if (mapping) {
+			arm_iommu_detach_device(dev);
+			arm_iommu_release_mapping(mapping);
+		}
+	}
+
 	ret = iommu_attach_device(private->domain, dev);
 	if (ret) {
 		DRM_DEV_ERROR(dev, "Failed to attach iommu device\n");
-- 
2.25.1