[PATCH 6/7] ARM: dma: Use dma_pfn_offset for dma address translation

[Santosh Shilimkar]

From: Grygorii Strashko <grygorii.strashko at ti.com>

In most of cases DMA addresses can be performed using offset value of
 Bus address space relatively to physical address space as following:

PFN->DMA:
 __pfn_to_phys(pfn + [-]dma_pfn_offset)

DMA->PFN:
 __phys_to_pfn(dma_addr) + [-]dma_pfn_offset

Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: Russell King <linux at arm.linux.org.uk>
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: Olof Johansson <olof at lixom.net>
Cc: Grant Likely <grant.likely at linaro.org>
Cc: Rob Herring <robh+dt at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Linus Walleij <linus.walleij at linaro.org>
Signed-off-by: Grygorii Strashko <grygorii.strashko at ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar at ti.com>
---
 arch/arm/include/asm/dma-mapping.h |   17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index e701a4d..8c12149 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -58,22 +58,31 @@ static inline int dma_set_mask(struct device *dev, u64 mask)
 #ifndef __arch_pfn_to_dma
 static inline dma_addr_t pfn_to_dma(struct device *dev, unsigned long pfn)
 {
-	return (dma_addr_t)__pfn_to_bus(pfn);
+	if (!dev)
+		return DMA_ERROR_CODE;
+	return (dma_addr_t)__pfn_to_bus(pfn - dev->dma_pfn_offset);
 }
 
 static inline unsigned long dma_to_pfn(struct device *dev, dma_addr_t addr)
 {
-	return __bus_to_pfn(addr);
+	if (!dev)
+		return 0;
+	return __bus_to_pfn(addr) + dev->dma_pfn_offset;
 }
 
 static inline void *dma_to_virt(struct device *dev, dma_addr_t addr)
 {
-	return (void *)__bus_to_virt((unsigned long)addr);
+	if (!dev)
+		return NULL;
+	return (void *)__bus_to_virt(__pfn_to_bus(dma_to_pfn(dev, addr)));
 }
 
 static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
 {
-	return (dma_addr_t)__virt_to_bus((unsigned long)(addr));
+	if (!dev)
+		return DMA_ERROR_CODE;
+	return pfn_to_dma(dev,
+			   __bus_to_pfn(__virt_to_bus((unsigned long)(addr))));
 }
 
 #else
-- 
1.7.9.5