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Commit 1d990882 authored by FUJITA Tomonori's avatar FUJITA Tomonori Committed by Ingo Molnar
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x86: restore old GART alloc_coherent behavior 

Currently, GART alloc_coherent tries to allocate pages with GFP_DMA32
for a device having dma_masks > 24bit < 32bits. If GART gets an
address that a device can't access to, GART try to map the address to
a virtual I/O address that the device can access to.

But Andi pointed out, "The GART is somewhere in the 4GB range so you
cannot use it to map anything < 4GB. Also GART is pretty small."

http://lkml.org/lkml/2008/9/12/43



That is, it's possible that GART doesn't have virtual I/O address
space that a device can access to. The above behavior doesn't work for
a device having dma_masks > 24bit < 32bits.

This patch restores old GART alloc_coherent behavior (before the
alloc_coherent rewrite).

Signed-off-by: default avatarFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent ecef533e

arch/x86/kernel/pci-gart_64.c

+20 −23
Original line number Diff line number Diff line
@@ -487,31 +487,28 @@ static void * 
gart_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_addr,

		    gfp_t flag)

{

	void *vaddr;

	dma_addr_t paddr;

	unsigned long align_mask;

	u64 dma_mask = dma_alloc_coherent_mask(dev, flag);

	struct page *page;



	vaddr = (void *)__get_free_pages(flag | __GFP_ZERO, get_order(size));

	if (!vaddr)

	if (force_iommu && !(flag & GFP_DMA)) {

		flag &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);

		page = alloc_pages(flag | __GFP_ZERO, get_order(size));

		if (!page)

			return NULL;



	paddr = virt_to_phys(vaddr);

	if (is_buffer_dma_capable(dma_mask, paddr, size)) {

		*dma_addr = paddr;

		return vaddr;

	}



		align_mask = (1UL << get_order(size)) - 1;

		paddr = dma_map_area(dev, page_to_phys(page), size,

				     DMA_BIDIRECTIONAL, align_mask);



	*dma_addr = dma_map_area(dev, paddr, size, DMA_BIDIRECTIONAL,

				 align_mask);

		flush_gart();



	if (*dma_addr != bad_dma_address)

		return vaddr;



	free_pages((unsigned long)vaddr, get_order(size));

		if (paddr != bad_dma_address) {

			*dma_addr = paddr;

			return page_address(page);

		}

		__free_pages(page, get_order(size));

	} else

		return dma_generic_alloc_coherent(dev, size, dma_addr, flag);



	return NULL;

}