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

1 files changed, 20 insertions, 23 deletions

diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index 7e08e466b8a..25c94fb96d7 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -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);
-
-        vaddr = (void *)__get_free_pages(flag | __GFP_ZERO, get_order(size));
-        if (!vaddr)
-                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;
-
-        *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));
+        struct page *page;
+
+        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;
+
+                align_mask = (1UL << get_order(size)) - 1;
+                paddr = dma_map_area(dev, page_to_phys(page), size,
+                                     DMA_BIDIRECTIONAL, align_mask);
+
+                flush_gart();
+                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;
 }