arch/arm/mm/dma-mapping.c

Source file repositories/reference/linux-study-clean/arch/arm/mm/dma-mapping.c

File Facts

System
Linux kernel
Corpus path
arch/arm/mm/dma-mapping.c
Extension
.c
Size
43921 bytes
Lines
1750
Domain
Architecture Layer
Bucket
arch/arm
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

struct arm_dma_alloc_args {
	struct device *dev;
	size_t size;
	gfp_t gfp;
	pgprot_t prot;
	const void *caller;
	bool want_vaddr;
	int coherent_flag;
};

struct arm_dma_free_args {
	struct device *dev;
	size_t size;
	void *cpu_addr;
	struct page *page;
	bool want_vaddr;
};

#define NORMAL	    0
#define COHERENT    1

struct arm_dma_allocator {
	void *(*alloc)(struct arm_dma_alloc_args *args,
		       struct page **ret_page);
	void (*free)(struct arm_dma_free_args *args);
};

struct arm_dma_buffer {
	struct list_head list;
	void *virt;
	struct arm_dma_allocator *allocator;
};

static LIST_HEAD(arm_dma_bufs);
static DEFINE_SPINLOCK(arm_dma_bufs_lock);

static struct arm_dma_buffer *arm_dma_buffer_find(void *virt)
{
	struct arm_dma_buffer *buf, *found = NULL;
	unsigned long flags;

	spin_lock_irqsave(&arm_dma_bufs_lock, flags);
	list_for_each_entry(buf, &arm_dma_bufs, list) {
		if (buf->virt == virt) {
			list_del(&buf->list);
			found = buf;
			break;
		}
	}
	spin_unlock_irqrestore(&arm_dma_bufs_lock, flags);
	return found;
}

/*
 * The DMA API is built upon the notion of "buffer ownership".  A buffer
 * is either exclusively owned by the CPU (and therefore may be accessed
 * by it) or exclusively owned by the DMA device.  These helper functions
 * represent the transitions between these two ownership states.
 *
 * Note, however, that on later ARMs, this notion does not work due to
 * speculative prefetches.  We model our approach on the assumption that
 * the CPU does do speculative prefetches, which means we clean caches
 * before transfers and delay cache invalidation until transfer completion.
 *
 */

static void __dma_clear_buffer(struct page *page, size_t size, int coherent_flag)
{
	/*
	 * Ensure that the allocated pages are zeroed, and that any data
	 * lurking in the kernel direct-mapped region is invalidated.
	 */
	if (PageHighMem(page)) {
		phys_addr_t base = __pfn_to_phys(page_to_pfn(page));
		phys_addr_t end = base + size;
		while (size > 0) {
			void *ptr = kmap_atomic(page);
			memset(ptr, 0, PAGE_SIZE);
			if (coherent_flag != COHERENT)
				dmac_flush_range(ptr, ptr + PAGE_SIZE);
			kunmap_atomic(ptr);
			page++;
			size -= PAGE_SIZE;
		}
		if (coherent_flag != COHERENT)
			outer_flush_range(base, end);
	} else {
		void *ptr = page_address(page);
		memset(ptr, 0, size);
		if (coherent_flag != COHERENT) {

Annotation

Implementation Notes