SPARC64: Fix sun4v DMA panic

64bit DMA only supported on sun4v equipped with ATU IOMMU HW.
'Commit b02c2b0bfd7ae ("sparc: remove arch specific dma_supported
implementations")' introduced a code that incorrectly allow
dma_supported() to succeed for 64bit dma mask even if system doesn't
have ATU IOMMU. This results into panic.

Fix it.

Reported-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Tushar Dave <tushar.n.dave@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
index 24f21c726dfa..f10e2f712394 100644
--- a/arch/sparc/kernel/pci_sun4v.c
+++ b/arch/sparc/kernel/pci_sun4v.c
@@ -673,12 +673,14 @@ static void dma_4v_unmap_sg(struct device *dev, struct scatterlist *sglist,
 static int dma_4v_supported(struct device *dev, u64 device_mask)
 {
         struct iommu *iommu = dev->archdata.iommu;
-        u64 dma_addr_mask;
+        u64 dma_addr_mask = iommu->dma_addr_mask;
 
-        if (device_mask > DMA_BIT_MASK(32) && iommu->atu)
-                dma_addr_mask = iommu->atu->dma_addr_mask;
-        else
-                dma_addr_mask = iommu->dma_addr_mask;
+        if (device_mask > DMA_BIT_MASK(32)) {
+                if (iommu->atu)
+                        dma_addr_mask = iommu->atu->dma_addr_mask;
+                else
+                        return 0;
+        }
 
         if ((device_mask & dma_addr_mask) == dma_addr_mask)
                 return 1;