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-rw-r--r--kernel/dma-coherent.c42
1 files changed, 31 insertions, 11 deletions
diff --git a/kernel/dma-coherent.c b/kernel/dma-coherent.c
index f013a0c..0387074 100644
--- a/kernel/dma-coherent.c
+++ b/kernel/dma-coherent.c
@@ -109,20 +109,40 @@ EXPORT_SYMBOL(dma_mark_declared_memory_occupied);
int dma_alloc_from_coherent(struct device *dev, ssize_t size,
dma_addr_t *dma_handle, void **ret)
{
- struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL;
+ struct dma_coherent_mem *mem;
int order = get_order(size);
+ int pageno;
- if (mem) {
- int page = bitmap_find_free_region(mem->bitmap, mem->size,
- order);
- if (page >= 0) {
- *dma_handle = mem->device_base + (page << PAGE_SHIFT);
- *ret = mem->virt_base + (page << PAGE_SHIFT);
- memset(*ret, 0, size);
- } else if (mem->flags & DMA_MEMORY_EXCLUSIVE)
- *ret = NULL;
+ if (!dev)
+ return 0;
+ mem = dev->dma_mem;
+ if (!mem)
+ return 0;
+ if (unlikely(size > mem->size))
+ return 0;
+
+ pageno = bitmap_find_free_region(mem->bitmap, mem->size, order);
+ if (pageno >= 0) {
+ /*
+ * Memory was found in the per-device arena.
+ */
+ *dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
+ *ret = mem->virt_base + (pageno << PAGE_SHIFT);
+ memset(*ret, 0, size);
+ } else if (mem->flags & DMA_MEMORY_EXCLUSIVE) {
+ /*
+ * The per-device arena is exhausted and we are not
+ * permitted to fall back to generic memory.
+ */
+ *ret = NULL;
+ } else {
+ /*
+ * The per-device arena is exhausted and we are
+ * permitted to fall back to generic memory.
+ */
+ return 0;
}
- return (mem != NULL);
+ return 1;
}
EXPORT_SYMBOL(dma_alloc_from_coherent);
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