[PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device
Christoph Hellwig
hch at lst.de
Sat Mar 21 01:16:39 AEDT 2020
Several IOMMU drivers have a bypass mode where they can use a direct
mapping if the devices DMA mask is large enough. Add generic support
to the core dma-mapping code to do that to switch those drivers to
a common solution.
Signed-off-by: Christoph Hellwig <hch at lst.de>
---
include/linux/device.h | 6 ++++++
include/linux/dma-mapping.h | 30 ++++++++++++++++++------------
kernel/dma/mapping.c | 36 +++++++++++++++++++++++++++---------
3 files changed, 51 insertions(+), 21 deletions(-)
diff --git a/include/linux/device.h b/include/linux/device.h
index 0cd7c647c16c..09be8bb2c4a6 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -525,6 +525,11 @@ struct dev_links_info {
* sync_state() callback.
* @dma_coherent: this particular device is dma coherent, even if the
* architecture supports non-coherent devices.
+ * @dma_ops_bypass: If set to %true then the dma_ops are bypassed for the
+ * streaming DMA operations (->map_* / ->unmap_* / ->sync_*),
+ * and optionall (if the coherent mask is large enough) also
+ * for dma allocations. This flag is managed by the dma ops
+ * instance from ->dma_supported.
*
* At the lowest level, every device in a Linux system is represented by an
* instance of struct device. The device structure contains the information
@@ -625,6 +630,7 @@ struct device {
defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
bool dma_coherent:1;
#endif
+ bool dma_ops_bypass : 1;
};
static inline struct device *kobj_to_dev(struct kobject *kobj)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 330ad58fbf4d..c3af0cf5e435 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -188,9 +188,15 @@ static inline int dma_mmap_from_global_coherent(struct vm_area_struct *vma,
}
#endif /* CONFIG_DMA_DECLARE_COHERENT */
-static inline bool dma_is_direct(const struct dma_map_ops *ops)
+/*
+ * Check if the devices uses a direct mapping for streaming DMA operations.
+ * This allows IOMMU drivers to set a bypass mode if the DMA mask is large
+ * enough.
+ */
+static inline bool dma_map_direct(struct device *dev,
+ const struct dma_map_ops *ops)
{
- return likely(!ops);
+ return likely(!ops) || dev->dma_ops_bypass;
}
/*
@@ -279,7 +285,7 @@ static inline dma_addr_t dma_map_page_attrs(struct device *dev,
dma_addr_t addr;
BUG_ON(!valid_dma_direction(dir));
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
else
addr = ops->map_page(dev, page, offset, size, dir, attrs);
@@ -294,7 +300,7 @@ static inline void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr,
const struct dma_map_ops *ops = get_dma_ops(dev);
BUG_ON(!valid_dma_direction(dir));
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
dma_direct_unmap_page(dev, addr, size, dir, attrs);
else if (ops->unmap_page)
ops->unmap_page(dev, addr, size, dir, attrs);
@@ -313,7 +319,7 @@ static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
int ents;
BUG_ON(!valid_dma_direction(dir));
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);
else
ents = ops->map_sg(dev, sg, nents, dir, attrs);
@@ -331,7 +337,7 @@ static inline void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg
BUG_ON(!valid_dma_direction(dir));
debug_dma_unmap_sg(dev, sg, nents, dir);
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
dma_direct_unmap_sg(dev, sg, nents, dir, attrs);
else if (ops->unmap_sg)
ops->unmap_sg(dev, sg, nents, dir, attrs);
@@ -352,7 +358,7 @@ static inline dma_addr_t dma_map_resource(struct device *dev,
if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
return DMA_MAPPING_ERROR;
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
else if (ops->map_resource)
addr = ops->map_resource(dev, phys_addr, size, dir, attrs);
@@ -368,7 +374,7 @@ static inline void dma_unmap_resource(struct device *dev, dma_addr_t addr,
const struct dma_map_ops *ops = get_dma_ops(dev);
BUG_ON(!valid_dma_direction(dir));
- if (!dma_is_direct(ops) && ops->unmap_resource)
+ if (!dma_map_direct(dev, ops) && ops->unmap_resource)
ops->unmap_resource(dev, addr, size, dir, attrs);
debug_dma_unmap_resource(dev, addr, size, dir);
}
@@ -380,7 +386,7 @@ static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
const struct dma_map_ops *ops = get_dma_ops(dev);
BUG_ON(!valid_dma_direction(dir));
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
dma_direct_sync_single_for_cpu(dev, addr, size, dir);
else if (ops->sync_single_for_cpu)
ops->sync_single_for_cpu(dev, addr, size, dir);
@@ -394,7 +400,7 @@ static inline void dma_sync_single_for_device(struct device *dev,
const struct dma_map_ops *ops = get_dma_ops(dev);
BUG_ON(!valid_dma_direction(dir));
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
dma_direct_sync_single_for_device(dev, addr, size, dir);
else if (ops->sync_single_for_device)
ops->sync_single_for_device(dev, addr, size, dir);
@@ -408,7 +414,7 @@ dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
const struct dma_map_ops *ops = get_dma_ops(dev);
BUG_ON(!valid_dma_direction(dir));
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
dma_direct_sync_sg_for_cpu(dev, sg, nelems, dir);
else if (ops->sync_sg_for_cpu)
ops->sync_sg_for_cpu(dev, sg, nelems, dir);
@@ -422,7 +428,7 @@ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
const struct dma_map_ops *ops = get_dma_ops(dev);
BUG_ON(!valid_dma_direction(dir));
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
dma_direct_sync_sg_for_device(dev, sg, nelems, dir);
else if (ops->sync_sg_for_device)
ops->sync_sg_for_device(dev, sg, nelems, dir);
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 12ff766ec1fa..fdea45574345 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -105,6 +105,24 @@ void *dmam_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
}
EXPORT_SYMBOL(dmam_alloc_attrs);
+static bool dma_alloc_direct(struct device *dev, const struct dma_map_ops *ops)
+{
+ if (!ops)
+ return true;
+
+ /*
+ * Allows IOMMU drivers to bypass dynamic translations if the DMA mask
+ * is large enough.
+ */
+ if (dev->dma_ops_bypass) {
+ if (min_not_zero(dev->coherent_dma_mask, dev->bus_dma_limit) >=
+ dma_direct_get_required_mask(dev))
+ return true;
+ }
+
+ return false;
+}
+
/*
* Create scatter-list for the already allocated DMA buffer.
*/
@@ -138,7 +156,7 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
{
const struct dma_map_ops *ops = get_dma_ops(dev);
- if (dma_is_direct(ops))
+ if (dma_alloc_direct(dev, ops))
return dma_direct_get_sgtable(dev, sgt, cpu_addr, dma_addr,
size, attrs);
if (!ops->get_sgtable)
@@ -206,7 +224,7 @@ bool dma_can_mmap(struct device *dev)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
- if (dma_is_direct(ops))
+ if (dma_alloc_direct(dev, ops))
return dma_direct_can_mmap(dev);
return ops->mmap != NULL;
}
@@ -231,7 +249,7 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
{
const struct dma_map_ops *ops = get_dma_ops(dev);
- if (dma_is_direct(ops))
+ if (dma_alloc_direct(dev, ops))
return dma_direct_mmap(dev, vma, cpu_addr, dma_addr, size,
attrs);
if (!ops->mmap)
@@ -244,7 +262,7 @@ u64 dma_get_required_mask(struct device *dev)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
return dma_direct_get_required_mask(dev);
if (ops->get_required_mask)
return ops->get_required_mask(dev);
@@ -275,7 +293,7 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
/* let the implementation decide on the zone to allocate from: */
flag &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM);
- if (dma_is_direct(ops))
+ if (dma_alloc_direct(dev, ops))
cpu_addr = dma_direct_alloc(dev, size, dma_handle, flag, attrs);
else if (ops->alloc)
cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
@@ -307,7 +325,7 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
return;
debug_dma_free_coherent(dev, size, cpu_addr, dma_handle);
- if (dma_is_direct(ops))
+ if (dma_alloc_direct(dev, ops))
dma_direct_free(dev, size, cpu_addr, dma_handle, attrs);
else if (ops->free)
ops->free(dev, size, cpu_addr, dma_handle, attrs);
@@ -318,7 +336,7 @@ int dma_supported(struct device *dev, u64 mask)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
- if (dma_is_direct(ops))
+ if (!ops)
return dma_direct_supported(dev, mask);
if (!ops->dma_supported)
return 1;
@@ -374,7 +392,7 @@ void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
BUG_ON(!valid_dma_direction(dir));
- if (dma_is_direct(ops))
+ if (dma_alloc_direct(dev, ops))
arch_dma_cache_sync(dev, vaddr, size, dir);
else if (ops->cache_sync)
ops->cache_sync(dev, vaddr, size, dir);
@@ -386,7 +404,7 @@ size_t dma_max_mapping_size(struct device *dev)
const struct dma_map_ops *ops = get_dma_ops(dev);
size_t size = SIZE_MAX;
- if (dma_is_direct(ops))
+ if (dma_map_direct(dev, ops))
size = dma_direct_max_mapping_size(dev);
else if (ops && ops->max_mapping_size)
size = ops->max_mapping_size(dev);
--
2.25.1
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