linux-kernel - [PATCH v3 03/24] powerpc/powernv: Do not set "read" flag if direction==DMA

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Message-Id: <1422523325-1389-4-git-send-email-aik@ozlabs.ru>
Date:	Thu, 29 Jan 2015 20:21:44 +1100
From:	Alexey Kardashevskiy <aik@...abs.ru>
To:	linuxppc-dev@...ts.ozlabs.org
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Gavin Shan <gwshan@...ux.vnet.ibm.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Alexander Graf <agraf@...e.de>,
	Alexander Gordeev <agordeev@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 03/24] powerpc/powernv: Do not set "read" flag if direction==DMA_NONE

Normally a bitmap from the iommu_table is used to track what TCE entry
is in use. Since we are going to use iommu_table without its locks and
do xchg() instead, it becomes essential not to put bits which are not
implied in the direction flag.

Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
Reviewed-by: David Gibson <david@...son.dropbear.id.au>
---
 arch/powerpc/platforms/powernv/pci.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index 4945e87..9ec7d68 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -589,19 +589,27 @@ struct pci_ops pnv_pci_ops = {
 	.write = pnv_pci_write_config,
 };
 
+static unsigned long pnv_dmadir_to_flags(enum dma_data_direction direction)
+{
+	switch (direction) {
+	case DMA_BIDIRECTIONAL:
+	case DMA_FROM_DEVICE:
+		return TCE_PCI_READ | TCE_PCI_WRITE;
+	case DMA_TO_DEVICE:
+		return TCE_PCI_READ;
+	default:
+		return 0;
+	}
+}
+
 static int pnv_tce_build(struct iommu_table *tbl, long index, long npages,
 			 unsigned long uaddr, enum dma_data_direction direction,
 			 struct dma_attrs *attrs, bool rm)
 {
-	u64 proto_tce;
+	u64 proto_tce = pnv_dmadir_to_flags(direction);
 	__be64 *tcep, *tces;
 	u64 rpn;
 
-	proto_tce = TCE_PCI_READ; // Read allowed
-
-	if (direction != DMA_TO_DEVICE)
-		proto_tce |= TCE_PCI_WRITE;
-
 	tces = tcep = ((__be64 *)tbl->it_base) + index - tbl->it_offset;
 	rpn = __pa(uaddr) >> tbl->it_page_shift;
 
-- 
2.0.0

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