dma-mapping: consolidate the dma mmap implementations

The only functional differences (modulo a few missing fixes in the arch
code) is that architectures without coherent caches need a hook to
convert a virtual or dma address into a pfn, given that we don't have
the kernel linear mapping available for the otherwise easy virt_to_page
call.  As a side effect we can support mmap of the per-device coherent
area even on architectures not providing the callback, and we make
previous dangerous default methods dma_common_mmap actually save for
non-coherent architectures by rejecting it without the right helper.

In addition to that we need a hook so that some architectures can
override the protection bits when mmaping a dma coherent allocations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Paul Burton <paul.burton@mips.com> # MIPS parts

3 files changed, 27 insertions, 26 deletions

diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 5617c9a76208..645c7a2ecde8 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -29,13 +29,15 @@ config ARCH_HAS_SYNC_DMA_FOR_CPU
 config ARCH_HAS_SYNC_DMA_FOR_CPU_ALL
 	bool
 
-config DMA_DIRECT_OPS
+config ARCH_HAS_DMA_COHERENT_TO_PFN
 	bool
-	depends on HAS_DMA
 
-config DMA_NONCOHERENT_MMAP
+config ARCH_HAS_DMA_MMAP_PGPROT
 	bool
-	depends on DMA_DIRECT_OPS
+
+config DMA_DIRECT_OPS
+	bool
+	depends on HAS_DMA
 
 config DMA_NONCOHERENT_CACHE_SYNC
 	bool
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 09e85f6aa4ba..c954f0a6dc62 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -155,16 +155,6 @@ void dma_direct_free(struct device *dev, size_t size,
 		dma_direct_free_pages(dev, size, cpu_addr, dma_addr, attrs);
 }
 
-static int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
-		void *cpu_addr, dma_addr_t dma_addr, size_t size,
-		unsigned long attrs)
-{
-	if (!dev_is_dma_coherent(dev) &&
-	    IS_ENABLED(CONFIG_DMA_NONCOHERENT_MMAP))
-		return arch_dma_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
-	return dma_common_mmap(dev, vma, cpu_addr, dma_addr, size);
-}
-
 static void dma_direct_sync_single_for_device(struct device *dev,
 		dma_addr_t addr, size_t size, enum dma_data_direction dir)
 {
@@ -293,7 +283,6 @@ int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr)
 const struct dma_map_ops dma_direct_ops = {
 	.alloc			= dma_direct_alloc,
 	.free			= dma_direct_free,
-	.mmap			= dma_direct_mmap,
 	.map_page		= dma_direct_map_page,
 	.map_sg			= dma_direct_map_sg,
 #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 3540cb399bd2..42fd73aca305 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -7,7 +7,7 @@
  */
 
 #include <linux/acpi.h>
-#include <linux/dma-mapping.h>
+#include <linux/dma-noncoherent.h>
 #include <linux/export.h>
 #include <linux/gfp.h>
 #include <linux/of_device.h>
@@ -220,27 +220,37 @@ EXPORT_SYMBOL(dma_common_get_sgtable);
  * Create userspace mapping for the DMA-coherent memory.
  */
 int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
-		    void *cpu_addr, dma_addr_t dma_addr, size_t size)
+		void *cpu_addr, dma_addr_t dma_addr, size_t size,
+		unsigned long attrs)
 {
-	int ret = -ENXIO;
 #ifndef CONFIG_ARCH_NO_COHERENT_DMA_MMAP
 	unsigned long user_count = vma_pages(vma);
 	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	unsigned long off = vma->vm_pgoff;
+	unsigned long pfn;
+	int ret = -ENXIO;
 
-	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	vma->vm_page_prot = arch_dma_mmap_pgprot(dev, vma->vm_page_prot, attrs);
 
 	if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
 		return ret;
 
-	if (off < count && user_count <= (count - off))
-		ret = remap_pfn_range(vma, vma->vm_start,
-				      page_to_pfn(virt_to_page(cpu_addr)) + off,
-				      user_count << PAGE_SHIFT,
-				      vma->vm_page_prot);
-#endif	/* !CONFIG_ARCH_NO_COHERENT_DMA_MMAP */
+	if (off >= count || user_count > count - off)
+		return -ENXIO;
+
+	if (!dev_is_dma_coherent(dev)) {
+		if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_COHERENT_TO_PFN))
+			return -ENXIO;
+		pfn = arch_dma_coherent_to_pfn(dev, cpu_addr, dma_addr);
+	} else {
+		pfn = page_to_pfn(virt_to_page(cpu_addr));
+	}
 
-	return ret;
+	return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
+			user_count << PAGE_SHIFT, vma->vm_page_prot);
+#else
+	return -ENXIO;
+#endif /* !CONFIG_ARCH_NO_COHERENT_DMA_MMAP */
 }
 EXPORT_SYMBOL(dma_common_mmap);