On 30/05/18 09:03, Thierry Reding wrote:
From: Thierry Reding <treding@xxxxxxxxxx>
Implement this function to enable drivers from detaching from any IOMMU
domains that architecture code might have attached them to so that they
can take exclusive control of the IOMMU via the IOMMU API.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
Changes in v3:
- make API 32-bit ARM specific
- avoid extra local variable
Changes in v2:
- fix compilation
arch/arm/include/asm/dma-mapping.h | 3 +++
arch/arm/mm/dma-mapping-nommu.c | 4 ++++
arch/arm/mm/dma-mapping.c | 16 ++++++++++++++++
3 files changed, 23 insertions(+)
diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index 8436f6ade57d..5960e9f3a9d0 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -103,6 +103,9 @@ extern void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
#define arch_teardown_dma_ops arch_teardown_dma_ops
extern void arch_teardown_dma_ops(struct device *dev);
+#define arm_dma_iommu_detach_device arm_dma_iommu_detach_device
+extern void arm_dma_iommu_detach_device(struct device *dev);
+
/* do not use this function in a driver */
static inline bool is_device_dma_coherent(struct device *dev)
{
diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c
index f448a0663b10..eb781369377b 100644
--- a/arch/arm/mm/dma-mapping-nommu.c
+++ b/arch/arm/mm/dma-mapping-nommu.c
@@ -241,3 +241,7 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
void arch_teardown_dma_ops(struct device *dev)
{
}
+
+void arm_dma_iommu_detach_device(struct device *dev)
+{
+}
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index af27f1c22d93..6d8af08b3e7d 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -2400,3 +2400,19 @@ void arch_teardown_dma_ops(struct device *dev)
arm_teardown_iommu_dma_ops(dev);
}
+
+void arm_dma_iommu_detach_device(struct device *dev)
+{
+#ifdef CONFIG_ARM_DMA_USE_IOMMU
+ struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
+
+ if (!mapping)
+ return;
+
+ arm_iommu_release_mapping(mapping);
Potentially freeing the mapping before you try to operate on it is never
the best idea. Plus arm_iommu_detach_device() already releases a
reference appropriately anyway, so it's a double-free.
+ arm_iommu_detach_device(dev);
+
+ set_dma_ops(dev, arm_get_dma_map_ops(dev->archdata.dma_coherent));
+#endif
+}
+EXPORT_SYMBOL(arm_dma_iommu_detach_device);
I really don't see why we need an extra function that essentially just
duplicates arm_iommu_detach_device(). The only real difference here is
that here you reset the DMA ops more appropriately, but I think the
existing function should be fixed to do that anyway, since
set_dma_ops(dev, NULL) now just behaves as an unconditional fallback to
the noncoherent arm_dma_ops, which clearly isn't always right.
Robin.
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