drivers: dma-mapping: allow dma_common_mmap() for NOMMU

Currently, internals of dma_common_mmap() is compiled out if build is
done for either NOMMU or target which explicitly says it does not
have/want coherent DMA mmap. It turned out that dma_common_mmap() can
be handy in NOMMU setup (at least for ARM).

This patch converts exitent NOMMU targets to use ARCH_NO_COHERENT_DMA_MMAP,
thus when CONFIG_MMU is gone from dma_common_mmap() their behaviour stays
unchanged.

ARM is not converted to ARCH_NO_COHERENT_DMA_MMAP because it 1)
already has mmap callback which can handle (at some extent) NOMMU 2)
already defines dummy pgprot_noncached() for NOMMU build.

c6x and frv stay untouched since they already have ARCH_NO_COHERENT_DMA_MMAP.

Cc: Steven Miao <realmz6@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>

arch/blackfin/Kconfig

@@ -41,6 +41,7 @@ config BLACKFIN
 	select MODULES_USE_ELF_RELA
 	select HAVE_DEBUG_STACKOVERFLOW
 	select HAVE_NMI
+	select ARCH_NO_COHERENT_DMA_MMAP
 
 config GENERIC_CSUM
 	def_bool y

arch/m32r/Kconfig

@@ -19,6 +19,7 @@ config M32R
 	select HAVE_DEBUG_STACKOVERFLOW
 	select CPU_NO_EFFICIENT_FFS
 	select DMA_NOOP_OPS
+	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 
 config SBUS
 	bool

arch/m68k/Kconfig

@@ -2,6 +2,7 @@ config M68K
 	bool
 	default y
 	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
+	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select HAVE_IDE
 	select HAVE_AOUT if MMU
 	select HAVE_DEBUG_BUGVERBOSE

arch/microblaze/Kconfig

@@ -2,6 +2,7 @@ config MICROBLAZE
 	def_bool y
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_MIGHT_HAVE_PC_PARPORT
+	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_EXTABLE_SORT
 	select CLKSRC_OF

arch/sh/Kconfig

@@ -2,6 +2,7 @@ config SUPERH
 	def_bool y
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_MIGHT_HAVE_PC_PARPORT
+	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select HAVE_PATA_PLATFORM
 	select CLKDEV_LOOKUP
 	select HAVE_IDE if HAS_IOPORT_MAP

arch/xtensa/Kconfig

@@ -3,6 +3,7 @@ config ZONE_DMA
 
 config XTENSA
 	def_bool y
+	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_EXTABLE_SORT

drivers/base/dma-mapping.c

@@ -227,7 +227,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 		    void *cpu_addr, dma_addr_t dma_addr, size_t size)
 {
 	int ret = -ENXIO;
-#if defined(CONFIG_MMU) && !defined(CONFIG_ARCH_NO_COHERENT_DMA_MMAP)
+#ifndef CONFIG_ARCH_NO_COHERENT_DMA_MMAP
 	unsigned long user_count = vma_pages(vma);
 	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	unsigned long pfn = page_to_pfn(virt_to_page(cpu_addr));
@@ -244,7 +244,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 				      user_count << PAGE_SHIFT,
 				      vma->vm_page_prot);
 	}
-#endif	/* CONFIG_MMU && !CONFIG_ARCH_NO_COHERENT_DMA_MMAP */
+#endif	/* !CONFIG_ARCH_NO_COHERENT_DMA_MMAP */
 
 	return ret;
 }