drivers/dma/dw_dmac: make driver's endianness configurable

The dw_dmac driver was originally developed for avr32 to be used with the
Synopsys DesignWare AHB DMA controller.  Starting from 2.6.38, access to
the device's i/o memory was done with the little-endian readl/writel
functions(1)

This broke the driver for the avr32 platform, because it needs big
(native) endian accessors.  This patch makes the endianness configurable
using 'DW_DMAC_BIG_ENDIAN_IO', which will default be true for AVR32

I submitted this patch before(2) but then waited for Andy to finish other
changes to the same module(3).

(1) https://patchwork.kernel.org/patch/608211
(2) https://lkml.org/lkml/2012/8/26/148
(3) https://lkml.org/lkml/2012/9/21/173

Signed-off-by: Hein Tibosch <hein_tibosch@yahoo.es>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Ludovic Desroches <ludovic.desroches@atmel.com>
Cc: Havard Skinnemoen <havard@skinnemoen.net>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/dma/Kconfig

@@ -90,6 +90,17 @@ config DW_DMAC
 	  Support the Synopsys DesignWare AHB DMA controller.  This
 	  can be integrated in chips such as the Atmel AT32ap7000.
 
+config DW_DMAC_BIG_ENDIAN_IO
+	bool "Use big endian I/O register access"
+	default y if AVR32
+	depends on DW_DMAC
+	help
+	  Say yes here to use big endian I/O access when reading and writing
+	  to the DMA controller registers. This is needed on some platforms,
+	  like the Atmel AVR32 architecture.
+
+	  If unsure, use the default setting.
+
 config AT_HDMAC
 	tristate "Atmel AHB DMA support"
 	depends on ARCH_AT91

drivers/dma/dw_dmac_regs.h

@@ -98,9 +98,17 @@ struct dw_dma_regs {
 	u32	DW_PARAMS;
 };
 
+#ifdef CONFIG_DW_DMAC_BIG_ENDIAN_IO
+#define dma_readl_native ioread32be
+#define dma_writel_native iowrite32be
+#else
+#define dma_readl_native readl
+#define dma_writel_native writel
+#endif
+
 /* To access the registers in early stage of probe */
 #define dma_read_byaddr(addr, name) \
-	readl((addr) + offsetof(struct dw_dma_regs, name))
+	dma_readl_native((addr) + offsetof(struct dw_dma_regs, name))
 
 /* Bitfields in DW_PARAMS */
 #define DW_PARAMS_NR_CHAN	8		/* number of channels */
@@ -216,9 +224,9 @@ __dwc_regs(struct dw_dma_chan *dwc)
 }
 
 #define channel_readl(dwc, name) \
-	readl(&(__dwc_regs(dwc)->name))
+	dma_readl_native(&(__dwc_regs(dwc)->name))
 #define channel_writel(dwc, name, val) \
-	writel((val), &(__dwc_regs(dwc)->name))
+	dma_writel_native((val), &(__dwc_regs(dwc)->name))
 
 static inline struct dw_dma_chan *to_dw_dma_chan(struct dma_chan *chan)
 {
@@ -246,9 +254,9 @@ static inline struct dw_dma_regs __iomem *__dw_regs(struct dw_dma *dw)
 }
 
 #define dma_readl(dw, name) \
-	readl(&(__dw_regs(dw)->name))
+	dma_readl_native(&(__dw_regs(dw)->name))
 #define dma_writel(dw, name, val) \
-	writel((val), &(__dw_regs(dw)->name))
+	dma_writel_native((val), &(__dw_regs(dw)->name))
 
 #define channel_set_bit(dw, reg, mask) \
 	dma_writel(dw, reg, ((mask) << 8) | (mask))