SPARC64: Fix sun4v DMA panic

tndave · davem330 · commit 2ad67141f1e4 · 2017-07-12T08:13:04.000-07:00
64bit DMA only supported on sun4v equipped with ATU IOMMU HW. 'Commit b02c2b0 ("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>
diff --git 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;
