[U-Boot] [PATCH] ARM: asm: types: Introduce DMA_ADDR_T_64BIT

* [U-Boot] [PATCH] ARM: asm: types: Introduce DMA_ADDR_T_64BIT
@ 2016-03-24 10:32 Lokesh Vutla
  2016-03-25 22:59 ` Tom Rini
  2016-03-27 22:30 ` [U-Boot] " Tom Rini
  0 siblings, 2 replies; 3+ messages in thread
From: Lokesh Vutla @ 2016-03-24 10:32 UTC (permalink / raw)
  To: u-boot

dma_addr_t holds any valid DMA address. If the DMA API only uses 32-bit
addresses, dma_addr_t need only be 32 bits wide.  Bus addresses, e.g., PCI BARs,
may be wider than 32 bits, but drivers do memory-mapped I/O to ioremapped
kernel virtual addresses, so they don't care about the size of the actual
bus addresses.
Also 32 bit ARM systems with LPAE enabled can use 64bit address space, but
DMA still use 32bit address like in case of DRA7 and Keystone platforms.

This is inspired from the Linux kernel types implementation[1]

[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/linux/types.h#n142

Acked-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
---
 arch/arm/Kconfig             |  4 ++++
 arch/arm/include/asm/types.h | 17 +++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index e5f57ef..550ecde 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -7,6 +7,10 @@ config SYS_ARCH
 config ARM64
 	bool
 
+config DMA_ADDR_T_64BIT
+	bool
+	default y if ARM64
+
 config HAS_VBAR
         bool
 
diff --git a/arch/arm/include/asm/types.h b/arch/arm/include/asm/types.h
index 388058e..d108915 100644
--- a/arch/arm/include/asm/types.h
+++ b/arch/arm/include/asm/types.h
@@ -46,16 +46,29 @@ typedef unsigned long long u64;
 #endif	/* CONFIG_ARM64 */
 
 #ifdef CONFIG_PHYS_64BIT
-typedef unsigned long long dma_addr_t;
 typedef unsigned long long phys_addr_t;
 typedef unsigned long long phys_size_t;
 #else
 /* DMA addresses are 32-bits wide */
-typedef u32 dma_addr_t;
 typedef unsigned long phys_addr_t;
 typedef unsigned long phys_size_t;
 #endif
 
+/*
+ * A dma_addr_t can hold any valid DMA address, i.e., any address returned
+ * by the DMA API.
+ *
+ * If the DMA API only uses 32-bit addresses, dma_addr_t need only be 32
+ * bits wide.  Bus addresses, e.g., PCI BARs, may be wider than 32 bits,
+ * but drivers do memory-mapped I/O to ioremapped kernel virtual addresses,
+ * so they don't care about the size of the actual bus addresses.
+ */
+#ifdef CONFIG_DMA_ADDR_T_64BIT
+typedef unsigned long long dma_addr_t;
+#else
+typedef u32 dma_addr_t;
+#endif
+
 #endif /* __KERNEL__ */
 
 typedef unsigned long resource_size_t;
-- 
2.1.4

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