ARM: dma: Use dma_pfn_offset for dma address translation

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

Thanks to Russell King for suggesting the optimised macro's for
conversion.

Cc: Greg Kroah-Hartman <[email protected]>
Cc: Russell King <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Olof Johansson <[email protected]>
Cc: Grant Likely <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Linus Walleij <[email protected]>
Reviewed-by: Rob Herring <[email protected]>
Signed-off-by: Grygorii Strashko <[email protected]>
Signed-off-by: Santosh Shilimkar <[email protected]>

Author: grygoriyS

arch/arm/include/asm/dma-mapping.h

@@ -58,21 +58,37 @@ 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)
 {
+	if (dev)
+		pfn -= dev->dma_pfn_offset;
 	return (dma_addr_t)__pfn_to_bus(pfn);
 }
 
 static inline unsigned long dma_to_pfn(struct device *dev, dma_addr_t addr)
 {
-	return __bus_to_pfn(addr);
+	unsigned long pfn = __bus_to_pfn(addr);
+
+	if (dev)
+		pfn += dev->dma_pfn_offset;
+
+	return pfn;
 }
 
 static inline void *dma_to_virt(struct device *dev, dma_addr_t addr)
 {
+	if (dev) {
+		unsigned long pfn = dma_to_pfn(dev, addr);
+
+		return phys_to_virt(__pfn_to_phys(pfn));
+	}
+
 	return (void *)__bus_to_virt((unsigned long)addr);
 }
 
 static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
 {
+	if (dev)
+		return pfn_to_dma(dev, virt_to_pfn(addr));
+
 	return (dma_addr_t)__virt_to_bus((unsigned long)(addr));
 }