x86 gart: allocate size-aligned address for alloc_coherent, v2

This patch changes GART IOMMU to return a size aligned address wrt
dma_alloc_coherent, as DMA-mapping.txt defines:

The cpu return address and the DMA bus master address are both
guaranteed to be aligned to the smallest PAGE_SIZE order which
is greater than or equal to the requested size.  This invariant
exists (for example) to guarantee that if you allocate a chunk
which is smaller than or equal to 64 kilobytes, the extent of the
buffer you receive will not cross a 64K boundary.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/pci-gart_64.c

@@ -82,7 +82,8 @@ AGPEXTERN __u32 *agp_gatt_table;
 static unsigned long next_bit;  /* protected by iommu_bitmap_lock */
 static int need_flush;		/* global flush state. set for each gart wrap */
 
-static unsigned long alloc_iommu(struct device *dev, int size)
+static unsigned long alloc_iommu(struct device *dev, int size,
+				 unsigned long align_mask)
 {
 	unsigned long offset, flags;
 	unsigned long boundary_size;
@@ -95,11 +96,12 @@ static unsigned long alloc_iommu(struct device *dev, int size)
 
 	spin_lock_irqsave(&iommu_bitmap_lock, flags);
 	offset = iommu_area_alloc(iommu_gart_bitmap, iommu_pages, next_bit,
-				  size, base_index, boundary_size, 0);
+				  size, base_index, boundary_size, align_mask);
 	if (offset == -1) {
 		need_flush = 1;
 		offset = iommu_area_alloc(iommu_gart_bitmap, iommu_pages, 0,
-					  size, base_index, boundary_size, 0);
+					  size, base_index, boundary_size,
+					  align_mask);
 	}
 	if (offset != -1) {
 		next_bit = offset+size;
@@ -236,10 +238,10 @@ nonforced_iommu(struct device *dev, unsigned long addr, size_t size)
  * Caller needs to check if the iommu is needed and flush.
  */
 static dma_addr_t dma_map_area(struct device *dev, dma_addr_t phys_mem,
-				size_t size, int dir)
+				size_t size, int dir, unsigned long align_mask)
 {
 	unsigned long npages = iommu_num_pages(phys_mem, size);
-	unsigned long iommu_page = alloc_iommu(dev, npages);
+	unsigned long iommu_page = alloc_iommu(dev, npages, align_mask);
 	int i;
 
 	if (iommu_page == -1) {
@@ -262,7 +264,11 @@ static dma_addr_t dma_map_area(struct device *dev, dma_addr_t phys_mem,
 static dma_addr_t
 gart_map_simple(struct device *dev, phys_addr_t paddr, size_t size, int dir)
 {
-	dma_addr_t map = dma_map_area(dev, paddr, size, dir);
+	dma_addr_t map;
+	unsigned long align_mask;
+
+	align_mask = (1UL << get_order(size)) - 1;
+	map = dma_map_area(dev, paddr, size, dir, align_mask);
 
 	flush_gart();
 
@@ -281,7 +287,8 @@ gart_map_single(struct device *dev, phys_addr_t paddr, size_t size, int dir)
 	if (!need_iommu(dev, paddr, size))
 		return paddr;
 
-	bus = gart_map_simple(dev, paddr, size, dir);
+	bus = dma_map_area(dev, paddr, size, dir, 0);
+	flush_gart();
 
 	return bus;
 }
@@ -340,7 +347,7 @@ static int dma_map_sg_nonforce(struct device *dev, struct scatterlist *sg,
 		unsigned long addr = sg_phys(s);
 
 		if (nonforced_iommu(dev, addr, s->length)) {
-			addr = dma_map_area(dev, addr, s->length, dir);
+			addr = dma_map_area(dev, addr, s->length, dir, 0);
 			if (addr == bad_dma_address) {
 				if (i > 0)
 					gart_unmap_sg(dev, sg, i, dir);
@@ -362,7 +369,7 @@ static int __dma_map_cont(struct device *dev, struct scatterlist *start,
 			  int nelems, struct scatterlist *sout,
 			  unsigned long pages)
 {
-	unsigned long iommu_start = alloc_iommu(dev, pages);
+	unsigned long iommu_start = alloc_iommu(dev, pages, 0);
 	unsigned long iommu_page = iommu_start;
 	struct scatterlist *s;
 	int i;