Hi Thierry,
On 16/09/2019 16:04, Thierry Reding wrote:
From: Thierry Reding <treding@xxxxxxxxxx>
If the GPU is already attached to an IOMMU, don't detach it and setup an
explicit IOMMU domain. Since Nouveau can now properly handle the case of
the DMA API being backed by an IOMMU, just continue using the DMA API.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
.../drm/nouveau/nvkm/engine/device/tegra.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/device/tegra.c b/drivers/gpu/drm/nouveau/nvkm/engine/device/tegra.c
index d0d52c1d4aee..fc652aaa41c7 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/device/tegra.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/device/tegra.c
@@ -23,10 +23,6 @@
#ifdef CONFIG_NOUVEAU_PLATFORM_DRIVER
#include "priv.h"
-#if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)
-#include <asm/dma-iommu.h>
-#endif
-
static int
nvkm_device_tegra_power_up(struct nvkm_device_tegra *tdev)
{
@@ -109,14 +105,13 @@ nvkm_device_tegra_probe_iommu(struct nvkm_device_tegra *tdev)
unsigned long pgsize_bitmap;
int ret;
-#if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)
- if (dev->archdata.mapping) {
- struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
-
- arm_iommu_detach_device(dev);
- arm_iommu_release_mapping(mapping);
- }
-#endif
+ /*
+ * Skip explicit IOMMU initialization if the GPU is already attached
+ * to an IOMMU domain. This can happen if the DMA API is backed by an
+ * IOMMU.
+ */
+ if (iommu_get_domain_for_dev(dev))
+ return;
Beware of "iommu.passthrough=1" - you could get a valid default domain
here yet still have direct/SWIOTLB DMA ops. I guess you probably want to
double-check the domain type as well.
Robin.
if (!tdev->func->iommu_bit)
return;
