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ARM: dma-mapping: remove offset parameter to prepare for generic dma_ops
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This patch removes the need for the offset parameter in dma bounce
functions. This is required to let dma-mapping framework on ARM
architecture to use common, generic dma_map_ops based dma-mapping
helpers.

Background and more detailed explaination:

dma_*_range_* functions are available from the early days of the dma
mapping api. They are the correct way of doing a partial syncs on the
buffer (usually used by the network device drivers). This patch changes
only the internal implementation of the dma bounce functions to let
them tunnel through dma_map_ops structure. The driver api stays
unchanged, so driver are obliged to call dma_*_range_* functions to
keep code clean and easy to understand.

The only drawback from this patch is reduced detection of the dma api
abuse. Let us consider the following code:

dma_addr = dma_map_single(dev, ptr, 64, DMA_TO_DEVICE);
dma_sync_single_range_for_cpu(dev, dma_addr+16, 0, 32, DMA_TO_DEVICE);

Without the patch such code fails, because dma bounce code is unable
to find the bounce buffer for the given dma_address. After the patch
the above sync call will be equivalent to:

dma_sync_single_range_for_cpu(dev, dma_addr, 16, 32, DMA_TO_DEVICE);

which succeeds.

I don't consider this as a real problem, because DMA API abuse should be
caught by debug_dma_* function family. This patch lets us to simplify
the internal low-level implementation without chaning the driver visible
API.

Signed-off-by: Marek Szyprowski <[email protected]>
Acked-by: Kyungmin Park <[email protected]>
Tested-By: Subash Patel <[email protected]>
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@mszyprow
mszyprow committed May 21, 2012
1 parent 553ac78 commit a227fb9
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Showing 3 changed files with 45 additions and 39 deletions.
13 changes: 10 additions & 3 deletions arch/arm/common/dmabounce.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -173,7 +173,8 @@ find_safe_buffer(struct dmabounce_device_info *device_info, dma_addr_t safe_dma_
read_lock_irqsave(&device_info->lock, flags);

list_for_each_entry(b, &device_info->safe_buffers, node)
if (b->safe_dma_addr == safe_dma_addr) {
if (b->safe_dma_addr <= safe_dma_addr &&
b->safe_dma_addr + b->size > safe_dma_addr) {
rb = b;
break;
}
Expand Down Expand Up @@ -362,9 +363,10 @@ void __dma_unmap_page(struct device *dev, dma_addr_t dma_addr, size_t size,
EXPORT_SYMBOL(__dma_unmap_page);

int dmabounce_sync_for_cpu(struct device *dev, dma_addr_t addr,
unsigned long off, size_t sz, enum dma_data_direction dir)
size_t sz, enum dma_data_direction dir)
{
struct safe_buffer *buf;
unsigned long off;

dev_dbg(dev, "%s(dma=%#x,off=%#lx,sz=%zx,dir=%x)\n",
__func__, addr, off, sz, dir);
Expand All @@ -373,6 +375,8 @@ int dmabounce_sync_for_cpu(struct device *dev, dma_addr_t addr,
if (!buf)
return 1;

off = addr - buf->safe_dma_addr;

BUG_ON(buf->direction != dir);

dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
Expand All @@ -391,9 +395,10 @@ int dmabounce_sync_for_cpu(struct device *dev, dma_addr_t addr,
EXPORT_SYMBOL(dmabounce_sync_for_cpu);

int dmabounce_sync_for_device(struct device *dev, dma_addr_t addr,
unsigned long off, size_t sz, enum dma_data_direction dir)
size_t sz, enum dma_data_direction dir)
{
struct safe_buffer *buf;
unsigned long off;

dev_dbg(dev, "%s(dma=%#x,off=%#lx,sz=%zx,dir=%x)\n",
__func__, addr, off, sz, dir);
Expand All @@ -402,6 +407,8 @@ int dmabounce_sync_for_device(struct device *dev, dma_addr_t addr,
if (!buf)
return 1;

off = addr - buf->safe_dma_addr;

BUG_ON(buf->direction != dir);

dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
Expand Down
67 changes: 33 additions & 34 deletions arch/arm/include/asm/dma-mapping.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -266,19 +266,17 @@ extern void __dma_unmap_page(struct device *, dma_addr_t, size_t,
/*
* Private functions
*/
int dmabounce_sync_for_cpu(struct device *, dma_addr_t, unsigned long,
size_t, enum dma_data_direction);
int dmabounce_sync_for_device(struct device *, dma_addr_t, unsigned long,
size_t, enum dma_data_direction);
int dmabounce_sync_for_cpu(struct device *, dma_addr_t, size_t, enum dma_data_direction);
int dmabounce_sync_for_device(struct device *, dma_addr_t, size_t, enum dma_data_direction);
#else
static inline int dmabounce_sync_for_cpu(struct device *d, dma_addr_t addr,
unsigned long offset, size_t size, enum dma_data_direction dir)
size_t size, enum dma_data_direction dir)
{
return 1;
}

static inline int dmabounce_sync_for_device(struct device *d, dma_addr_t addr,
unsigned long offset, size_t size, enum dma_data_direction dir)
size_t size, enum dma_data_direction dir)
{
return 1;
}
Expand Down Expand Up @@ -401,6 +399,33 @@ static inline void dma_unmap_page(struct device *dev, dma_addr_t handle,
__dma_unmap_page(dev, handle, size, dir);
}


static inline void dma_sync_single_for_cpu(struct device *dev,
dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
BUG_ON(!valid_dma_direction(dir));

debug_dma_sync_single_for_cpu(dev, handle, size, dir);

if (!dmabounce_sync_for_cpu(dev, handle, size, dir))
return;

__dma_single_dev_to_cpu(dma_to_virt(dev, handle), size, dir);
}

static inline void dma_sync_single_for_device(struct device *dev,
dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
BUG_ON(!valid_dma_direction(dir));

debug_dma_sync_single_for_device(dev, handle, size, dir);

if (!dmabounce_sync_for_device(dev, handle, size, dir))
return;

__dma_single_cpu_to_dev(dma_to_virt(dev, handle), size, dir);
}

/**
* dma_sync_single_range_for_cpu
* @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
Expand All @@ -423,40 +448,14 @@ static inline void dma_sync_single_range_for_cpu(struct device *dev,
dma_addr_t handle, unsigned long offset, size_t size,
enum dma_data_direction dir)
{
BUG_ON(!valid_dma_direction(dir));

debug_dma_sync_single_for_cpu(dev, handle + offset, size, dir);

if (!dmabounce_sync_for_cpu(dev, handle, offset, size, dir))
return;

__dma_single_dev_to_cpu(dma_to_virt(dev, handle) + offset, size, dir);
dma_sync_single_for_cpu(dev, handle + offset, size, dir);
}

static inline void dma_sync_single_range_for_device(struct device *dev,
dma_addr_t handle, unsigned long offset, size_t size,
enum dma_data_direction dir)
{
BUG_ON(!valid_dma_direction(dir));

debug_dma_sync_single_for_device(dev, handle + offset, size, dir);

if (!dmabounce_sync_for_device(dev, handle, offset, size, dir))
return;

__dma_single_cpu_to_dev(dma_to_virt(dev, handle) + offset, size, dir);
}

static inline void dma_sync_single_for_cpu(struct device *dev,
dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
dma_sync_single_range_for_cpu(dev, handle, 0, size, dir);
}

static inline void dma_sync_single_for_device(struct device *dev,
dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
dma_sync_single_range_for_device(dev, handle, 0, size, dir);
dma_sync_single_for_device(dev, handle + offset, size, dir);
}

/*
Expand Down
4 changes: 2 additions & 2 deletions arch/arm/mm/dma-mapping.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -660,7 +660,7 @@ void dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
int i;

for_each_sg(sg, s, nents, i) {
if (!dmabounce_sync_for_cpu(dev, sg_dma_address(s), 0,
if (!dmabounce_sync_for_cpu(dev, sg_dma_address(s),
sg_dma_len(s), dir))
continue;

Expand All @@ -686,7 +686,7 @@ void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
int i;

for_each_sg(sg, s, nents, i) {
if (!dmabounce_sync_for_device(dev, sg_dma_address(s), 0,
if (!dmabounce_sync_for_device(dev, sg_dma_address(s),
sg_dma_len(s), dir))
continue;

Expand Down

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