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dma-mapping: Allow mixing bypass and mapped DMA operation 

At the moment we allow bypassing DMA ops only when we can do this for
the entire RAM. However there are configs with mixed type memory
where we could still allow bypassing IOMMU in most cases;
POWERPC with persistent memory is one example.

This adds an arch hook to determine where bypass can still work and
we invoke direct DMA API. The following patch checks the bus limit
on POWERPC to allow or disallow direct mapping.

This adds a ARCH_HAS_DMA_MAP_DIRECT config option to make the arch_xxxx
hooks no-op by default.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Alexey Kardashevskiy 2020-10-29 12:52:40 +11:00 committed by Christoph Hellwig
parent 418baf2c28
commit 8d8d53cf8f
3 changed files with 26 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/linux/dma-map-ops.h
View File

@ -314,6 +314,20 @@ static inline void arch_dma_mark_clean(phys_addr_t paddr, size_t size)
void *arch_dma_set_uncached(void *addr, size_t size);
void arch_dma_clear_uncached(void *addr, size_t size);
#ifdef CONFIG_ARCH_HAS_DMA_MAP_DIRECT
bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr);
bool arch_dma_unmap_page_direct(struct device *dev, dma_addr_t dma_handle);
bool arch_dma_map_sg_direct(struct device *dev, struct scatterlist *sg,
int nents);
bool arch_dma_unmap_sg_direct(struct device *dev, struct scatterlist *sg,
int nents);
#else
#define arch_dma_map_page_direct(d, a) (false)
#define arch_dma_unmap_page_direct(d, a) (false)
#define arch_dma_map_sg_direct(d, s, n) (false)
#define arch_dma_unmap_sg_direct(d, s, n) (false)
#endif
#ifdef CONFIG_ARCH_HAS_SETUP_DMA_OPS
void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
const struct iommu_ops *iommu, bool coherent);

4
kernel/dma/Kconfig
View File

@ -20,6 +20,10 @@ config DMA_OPS
config DMA_OPS_BYPASS
bool
# Lets platform IOMMU driver choose between bypass and IOMMU
config ARCH_HAS_DMA_MAP_DIRECT
bool
config NEED_SG_DMA_LENGTH
bool

12
kernel/dma/mapping.c
View File

@ -149,7 +149,8 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
if (WARN_ON_ONCE(!dev->dma_mask))
return DMA_MAPPING_ERROR;
if (dma_map_direct(dev, ops))
if (dma_map_direct(dev, ops) ||
arch_dma_map_page_direct(dev, page_to_phys(page) + offset + size))
addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
else
addr = ops->map_page(dev, page, offset, size, dir, attrs);
@ -165,7 +166,8 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
const struct dma_map_ops *ops = get_dma_ops(dev);
BUG_ON(!valid_dma_direction(dir));
if (dma_map_direct(dev, ops))
if (dma_map_direct(dev, ops) ||
arch_dma_unmap_page_direct(dev, addr + size))
dma_direct_unmap_page(dev, addr, size, dir, attrs);
else if (ops->unmap_page)
ops->unmap_page(dev, addr, size, dir, attrs);
@ -188,7 +190,8 @@ int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents,
if (WARN_ON_ONCE(!dev->dma_mask))
return 0;
if (dma_map_direct(dev, ops))
if (dma_map_direct(dev, ops) ||
arch_dma_map_sg_direct(dev, sg, nents))
ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);
else
ents = ops->map_sg(dev, sg, nents, dir, attrs);
@ -207,7 +210,8 @@ 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_map_direct(dev, ops))
if (dma_map_direct(dev, ops) ||
arch_dma_unmap_sg_direct(dev, sg, nents))
dma_direct_unmap_sg(dev, sg, nents, dir, attrs);
else if (ops->unmap_sg)
ops->unmap_sg(dev, sg, nents, dir, attrs);