ARM: dma-mapping: remove offset parameter to prepare for generic dma_ops

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 <m.szyprowski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Tested-By: Subash Patel <subash.ramaswamy@linaro.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/arch/arm/common/dmabounce.c b/arch/arm/common/dmabounce.c
index 210ad1bef7e5..32e9cc6ca7d9 100644
--- a/arch/arm/common/dmabounce.c
+++ b/arch/arm/common/dmabounce.c
@@ -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;
                 }
@@ -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);
@@ -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",
@@ -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);
@@ -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",