linux-kernel - [sparc-next] SPARC64: Fix sun4v DMA panic

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Date:   Tue, 11 Jul 2017 14:34:47 -0700
From:   Tushar Dave <tushar.n.dave@...cle.com>
To:     davem@...emloft.net, chris.hyser@...cle.com,
        sowmini.varadhan@...cle.com, egtvedt@...fundet.no,
        dan.carpenter@...cle.com, krzk@...nel.org,
        bart.vanassche@...disk.com, sparclinux@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, hch@....de, mroos@...ux.ee
Subject: [sparc-next] 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@...ux.ee>
Signed-off-by: Tushar Dave <tushar.n.dave@...cle.com>
---
 arch/sparc/kernel/pci_sun4v.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
index 24f21c7..f10e2f7 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;
-- 
1.9.1