Most dma_map_ops instances are IOMMUs that work perfectly fine in 32-bits
of IOVA space, and the generic direct mapping code already provides its
own routines that is intelligent based on the amount of memory actually
present. Wire up the dma-direct routine for the ARM direct mapping code
as well, and otherwise default to the constant 32-bit mask. This way
we only need to override it for the occasional odd IOMMU that requires
64-bit IOVA support, or IOMMU drivers that are more efficient if they
can fall back to the direct mapping.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
arch/arm/mm/dma-mapping.c | 3 +++
arch/powerpc/platforms/ps3/system-bus.c | 7 ------
arch/x86/kernel/amd_gart_64.c | 1 +
kernel/dma/mapping.c | 30 +++++++++----------------
4 files changed, 14 insertions(+), 27 deletions(-)
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 4410af33c5c4..9c9a23e5600d 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -14,6 +14,7 @@
#include <linux/list.h>
#include <linux/init.h>
#include <linux/device.h>
+#include <linux/dma-direct.h>
#include <linux/dma-mapping.h>
#include <linux/dma-noncoherent.h>
#include <linux/dma-contiguous.h>
@@ -192,6 +193,7 @@ const struct dma_map_ops arm_dma_ops = {
.sync_sg_for_cpu = arm_dma_sync_sg_for_cpu,
.sync_sg_for_device = arm_dma_sync_sg_for_device,
.dma_supported = arm_dma_supported,
+ .get_required_mask = dma_direct_get_required_mask,
};
EXPORT_SYMBOL(arm_dma_ops);
@@ -212,6 +214,7 @@ const struct dma_map_ops arm_coherent_dma_ops = {
.map_sg = arm_dma_map_sg,
.map_resource = dma_direct_map_resource,
.dma_supported = arm_dma_supported,
+ .get_required_mask = dma_direct_get_required_mask,
};
EXPORT_SYMBOL(arm_coherent_dma_ops);
diff --git a/arch/powerpc/platforms/ps3/system-bus.c b/arch/powerpc/platforms/ps3/system-bus.c
index 70fcc9736a8c..3542b7bd6a46 100644
--- a/arch/powerpc/platforms/ps3/system-bus.c
+++ b/arch/powerpc/platforms/ps3/system-bus.c
@@ -686,18 +686,12 @@ static int ps3_dma_supported(struct device *_dev, u64 mask)
return mask >= DMA_BIT_MASK(32);
}
-static u64 ps3_dma_get_required_mask(struct device *_dev)
-{
- return DMA_BIT_MASK(32);
-}
-
static const struct dma_map_ops ps3_sb_dma_ops = {
.alloc = ps3_alloc_coherent,
.free = ps3_free_coherent,
.map_sg = ps3_sb_map_sg,
.unmap_sg = ps3_sb_unmap_sg,
.dma_supported = ps3_dma_supported,
- .get_required_mask = ps3_dma_get_required_mask,
.map_page = ps3_sb_map_page,
.unmap_page = ps3_unmap_page,
.mmap = dma_common_mmap,
@@ -710,7 +704,6 @@ static const struct dma_map_ops ps3_ioc0_dma_ops = {
.map_sg = ps3_ioc0_map_sg,
.unmap_sg = ps3_ioc0_unmap_sg,
.dma_supported = ps3_dma_supported,
- .get_required_mask = ps3_dma_get_required_mask,
.map_page = ps3_ioc0_map_page,
.unmap_page = ps3_unmap_page,
.mmap = dma_common_mmap,
diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
index a65b4a9c7f87..d02662238b57 100644
--- a/arch/x86/kernel/amd_gart_64.c
+++ b/arch/x86/kernel/amd_gart_64.c
@@ -680,6 +680,7 @@ static const struct dma_map_ops gart_dma_ops = {
.dma_supported = dma_direct_supported,
.mmap = dma_common_mmap,
.get_sgtable = dma_common_get_sgtable,
+ .get_required_mask = dma_direct_get_required_mask,
};
static void gart_iommu_shutdown(void)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 47765c96fe09..96599f39f67a 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -247,25 +247,6 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
}
EXPORT_SYMBOL(dma_mmap_attrs);
-static u64 dma_default_get_required_mask(struct device *dev)
-{
- u32 low_totalram = ((max_pfn - 1) << PAGE_SHIFT);
- u32 high_totalram = ((max_pfn - 1) >> (32 - PAGE_SHIFT));
- u64 mask;
-
- if (!high_totalram) {
- /* convert to mask just covering totalram */
- low_totalram = (1 << (fls(low_totalram) - 1));
- low_totalram += low_totalram - 1;
- mask = low_totalram;
- } else {
- high_totalram = (1 << (fls(high_totalram) - 1));
- high_totalram += high_totalram - 1;
- mask = (((u64)high_totalram) << 32) + 0xffffffff;
- }
- return mask;
-}
-
u64 dma_get_required_mask(struct device *dev)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -274,7 +255,16 @@ u64 dma_get_required_mask(struct device *dev)
return dma_direct_get_required_mask(dev);
if (ops->get_required_mask)
return ops->get_required_mask(dev);
- return dma_default_get_required_mask(dev);
+
+ /*
+ * We require every DMA ops implementation to at least support a 32-bit
+ * DMA mask (and use bounce buffering if that isn't supported in
+ * hardware). As the direct mapping code has its own routine to
+ * actually report an optimal mask we default to 32-bit here as that
+ * is the right thing for most IOMMUs, and at least not actively
+ * harmful in general.
+ */
+ return DMA_BIT_MASK(32);
}
EXPORT_SYMBOL_GPL(dma_get_required_mask);
--
2.20.1
