ARM: dma-mapping: remove custom consistent dma region

This patch changes dma-mapping subsystem to use generic vmalloc areas
for all consistent dma allocations. This increases the total size limit
of the consistent allocations and removes platform hacks and a lot of
duplicated code.

Atomic allocations are served from special pool preallocated on boot,
because vmalloc areas cannot be reliably created in atomic context.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>

Documentation/kernel-parameters.txt

@@ -526,7 +526,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	coherent_pool=nn[KMG]	[ARM,KNL]
 			Sets the size of memory pool for coherent, atomic dma
-			allocations if Contiguous Memory Allocator (CMA) is used.
+			allocations, by default set to 256K.
 
 	code_bytes	[X86] How many bytes of object code to print
 			in an oops report.

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

@@ -226,7 +226,7 @@ static inline int dma_mmap_writecombine(struct device *dev, struct vm_area_struc
  * DMA region above it's default value of 2MB. It must be called before the
  * memory allocator is initialised, i.e. before any core_initcall.
  */
-extern void __init init_consistent_dma_size(unsigned long size);
+static inline void init_consistent_dma_size(unsigned long size) { }
 
 /*
  * For SA-1111, IXP425, and ADI systems  the dma-mapping functions are "magic"

arch/arm/mm/mm.h

@@ -59,6 +59,9 @@ extern void __flush_dcache_page(struct address_space *mapping, struct page *page
 #define VM_ARM_MTYPE(mt)		((mt) << 20)
 #define VM_ARM_MTYPE_MASK	(0x1f << 20)
 
+/* consistent regions used by dma_alloc_attrs() */
+#define VM_ARM_DMA_CONSISTENT	0x20000000
+
 #endif
 
 #ifdef CONFIG_ZONE_DMA

include/linux/vmalloc.h

@@ -93,6 +93,7 @@ extern struct vm_struct *__get_vm_area_caller(unsigned long size,
 					unsigned long start, unsigned long end,
 					const void *caller);
 extern struct vm_struct *remove_vm_area(const void *addr);
+extern struct vm_struct *find_vm_area(const void *addr);
 
 extern int map_vm_area(struct vm_struct *area, pgprot_t prot,
 			struct page ***pages);

mm/vmalloc.c

@@ -1403,7 +1403,15 @@ struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
 						-1, GFP_KERNEL, caller);
 }
 
-static struct vm_struct *find_vm_area(const void *addr)
+/**
+ *	find_vm_area  -  find a continuous kernel virtual area
+ *	@addr:		base address
+ *
+ *	Search for the kernel VM area starting at @addr, and return it.
+ *	It is up to the caller to do all required locking to keep the returned
+ *	pointer valid.
+ */
+struct vm_struct *find_vm_area(const void *addr)
 {
 	struct vmap_area *va;