[PATCH v2 3/9] arm64: Allow for different DMA and CPU bus offsets

From: Gerd Hoffmann
Date: Fri Jun 03 2016 - 02:19:58 EST


From: Alexander Graf <agraf@xxxxxxx>

On arm64, all SoCs we supported so far either have an IOMMU or have bus
addresses equal to CPU addresses.

However, with the Raspberry Pi 3 coming up, this is no longer true. To
allow DMA to work with an AArch64 kernel on those devices, let's allow
devices to have DMA offsets again.

Signed-off-by: Alexander Graf <agraf@xxxxxxx>
Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
---
arch/arm64/include/asm/dma-mapping.h | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h
index 7dbea6c..ccea82c 100644
--- a/arch/arm64/include/asm/dma-mapping.h
+++ b/arch/arm64/include/asm/dma-mapping.h
@@ -66,12 +66,16 @@ static inline bool is_device_dma_coherent(struct device *dev)

static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
{
- return (dma_addr_t)paddr;
+ dma_addr_t dev_addr = (dma_addr_t)paddr;
+
+ return dev_addr - ((dma_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
}

static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
{
- return (phys_addr_t)dev_addr;
+ phys_addr_t paddr = (phys_addr_t)dev_addr;
+
+ return paddr + ((phys_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
}

static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
@@ -86,5 +90,14 @@ static inline void dma_mark_clean(void *addr, size_t size)
{
}

+/* Override for dma_max_pfn() */
+static inline unsigned long dma_max_pfn(struct device *dev)
+{
+ dma_addr_t dma_max = (dma_addr_t)*dev->dma_mask;
+
+ return (ulong)dma_to_phys(dev, dma_max) >> PAGE_SHIFT;
+}
+#define dma_max_pfn(dev) dma_max_pfn(dev)
+
#endif /* __KERNEL__ */
#endif /* __ASM_DMA_MAPPING_H */
--
1.8.3.1