ARM: support generic per-device coherent dma mem

Signed-off-by: Dmitry Baryshkov <[e-mail]>
Cc: Jesse Barnes <[e-mail]>
Cc: Russell King <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

arch/arm/Kconfig

···
 	select HAVE_KRETPROBES if (HAVE_KPROBES)
 	select HAVE_FTRACE if (!XIP_KERNEL)
 	select HAVE_DYNAMIC_FTRACE if (HAVE_FTRACE)
+	select HAVE_GENERIC_DMA_COHERENT
 	help
 	  The ARM series is a line of low-power-consumption RISC chip designs
 	  licensed by ARM Ltd and targeted at embedded applications and

arch/arm/mm/consistent.c

···
 void *
 dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp)
 {
+	void *memory;
+
+	if (dma_alloc_from_coherent(dev, size, handle, &memory))
+		return memory;
+
 	if (arch_is_coherent()) {
 		void *virt;
 
···
 	u32 off;
 
 	WARN_ON(irqs_disabled());
+
+	if (dma_release_from_coherent(dev, get_order(size), cpu_addr))
+		return;
 
 	if (arch_is_coherent()) {
 		kfree(cpu_addr);

include/asm-arm/dma-mapping.h

···
 
 #include <linux/scatterlist.h>
 
+#include <asm-generic/dma-coherent.h>
+
 /*
  * DMA-consistent mapping functions.  These allocate/free a region of
  * uncached, unwrite-buffered mapped memory space for use with DMA