ARM: integrate CMA with DMA-mapping subsystem

This patch adds support for CMA to dma-mapping subsystem for ARM
architecture. By default a global CMA area is used, but specific devices
are allowed to have their private memory areas if required (they can be
created with dma_declare_contiguous() function during board
initialisation).

Contiguous memory areas reserved for DMA are remapped with 2-level page
tables on boot. Once a buffer is requested, a low memory kernel mapping
is updated to to match requested memory access type.

GFP_ATOMIC allocations are performed from special pool which is created
early during boot. This way remapping page attributes is not needed on
allocation time.

CMA has been enabled unconditionally for ARMv6+ systems.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
CC: Michal Nazarewicz <mina86@mina86.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Rob Clark <rob.clark@linaro.org>
Tested-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Robert Nelson <robertcnelson@gmail.com>
Tested-by: Barry Song <Baohua.Song@csr.com>

Documentation/kernel-parameters.txt

@@ -520,6 +520,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			a hypervisor.
 			Default: yes
 
+	coherent_pool=nn[KMG]	[ARM,KNL]
+			Sets the size of memory pool for coherent, atomic dma
+			allocations if Contiguous Memory Allocator (CMA) is used.
+
 	code_bytes	[X86] How many bytes of object code to print
 			in an oops report.
 			Range: 0 - 8192

arch/arm/Kconfig

@@ -4,6 +4,8 @@ config ARM
 	select HAVE_AOUT
 	select HAVE_DMA_API_DEBUG
 	select HAVE_IDE if PCI || ISA || PCMCIA
+	select HAVE_DMA_CONTIGUOUS if (CPU_V6 || CPU_V6K || CPU_V7)
+	select CMA if (CPU_V6 || CPU_V6K || CPU_V7)
 	select HAVE_MEMBLOCK
 	select RTC_LIB
 	select SYS_SUPPORTS_APM_EMULATION

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

@@ -0,0 +1,15 @@
+#ifndef ASMARM_DMA_CONTIGUOUS_H
+#define ASMARM_DMA_CONTIGUOUS_H
+
+#ifdef __KERNEL__
+#ifdef CONFIG_CMA
+
+#include <linux/types.h>
+#include <asm-generic/dma-contiguous.h>
+
+void dma_contiguous_early_fixup(phys_addr_t base, unsigned long size);
+
+#endif
+#endif
+
+#endif

arch/arm/include/asm/mach/map.h

@@ -30,6 +30,7 @@ struct map_desc {
 #define MT_MEMORY_DTCM		12
 #define MT_MEMORY_ITCM		13
 #define MT_MEMORY_SO		14
+#define MT_MEMORY_DMA_READY	15
 
 #ifdef CONFIG_MMU
 extern void iotable_init(struct map_desc *, int);

arch/arm/kernel/setup.c

@@ -81,6 +81,7 @@ __setup("fpe=", fpe_setup);
 extern void paging_init(struct machine_desc *desc);
 extern void sanity_check_meminfo(void);
 extern void reboot_setup(char *str);
+extern void setup_dma_zone(struct machine_desc *desc);
 
 unsigned int processor_id;
 EXPORT_SYMBOL(processor_id);
@@ -939,12 +940,8 @@ void __init setup_arch(char **cmdline_p)
 	machine_desc = mdesc;
 	machine_name = mdesc->name;
 
-#ifdef CONFIG_ZONE_DMA
-	if (mdesc->dma_zone_size) {
-		extern unsigned long arm_dma_zone_size;
-		arm_dma_zone_size = mdesc->dma_zone_size;
-	}
-#endif
+	setup_dma_zone(mdesc);
+
 	if (mdesc->restart_mode)
 		reboot_setup(&mdesc->restart_mode);