linux-kernel - [PATCH kernel v8 09/31] powerpc/powernv: Do not set "read" flag if direction==DMA

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Date:	Fri, 10 Apr 2015 16:30:51 +1000
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>,
	Alex Williamson <alex.williamson@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH kernel v8 09/31] 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.

This adds iommu_direction_to_tce_perm() (its counterpart is there already)
and uses it for powernv's pnv_tce_build().

Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
---
 arch/powerpc/include/asm/iommu.h     |  1 +
 arch/powerpc/kernel/iommu.c          | 15 +++++++++++++++
 arch/powerpc/platforms/powernv/pci.c |  7 +------
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
index ed69b7d..2af2d70 100644
--- a/arch/powerpc/include/asm/iommu.h
+++ b/arch/powerpc/include/asm/iommu.h
@@ -203,6 +203,7 @@ extern int iommu_take_ownership(struct iommu_table *tbl);
 extern void iommu_release_ownership(struct iommu_table *tbl);
 
 extern enum dma_data_direction iommu_tce_direction(unsigned long tce);
+extern unsigned long iommu_direction_to_tce_perm(enum dma_data_direction dir);
 
 #endif /* __KERNEL__ */
 #endif /* _ASM_IOMMU_H */
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 1b4a178..029b1ea 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -871,6 +871,21 @@ void iommu_free_coherent(struct iommu_table *tbl, size_t size,
 	}
 }
 
+unsigned long iommu_direction_to_tce_perm(enum dma_data_direction dir)
+{
+	switch (dir) {
+	case DMA_BIDIRECTIONAL:
+		return TCE_PCI_READ | TCE_PCI_WRITE;
+	case DMA_FROM_DEVICE:
+		return TCE_PCI_WRITE;
+	case DMA_TO_DEVICE:
+		return TCE_PCI_READ;
+	default:
+		return 0;
+	}
+}
+EXPORT_SYMBOL_GPL(iommu_direction_to_tce_perm);
+
 #ifdef CONFIG_IOMMU_API
 /*
  * SPAPR TCE API
diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index 54323d6..609f5b1 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -593,15 +593,10 @@ 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 = iommu_direction_to_tce_perm(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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