[PATCH 3/3] x86: restore old GART alloc_coherent behavior

FUJITA Tomonori
2008-09-24T11:53:15Z

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>
---
arch/x86/kernel/pci-gart_64.c | 43 +++++++++++++++++++---------------------
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 7e08e46..25c94fb 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;
}
--
1.5.4.2