[PATCH] mips: Add dma_mmap_coherent()

[Takashi Iwai <tiwai@suse.de>]

Hi,

I've been trying to fix a long-standing bug in ALSA, the mmap of
pages via dma_mmap_coherent().  Since the sound drivers need to expose
the whole buffer via mmap and the buffers are allocated via
dma_alloc_coherent(), it causes Oops on some architectures like MIPS.
One of the fix patches is this one, the addition of
dma_mmap_coherent() to MIPS architecture.

This implementation is pretty lazy (and untested) as you see below.

The whole patches are found on topic/dma-fix branch on sound-2.6 git
tree
  git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6.git

The gitweb URL of the branch is:
  
http://git.kernel.org/?p=linux/kernel/git/tiwai/sound-2.6.git;a=shortlog;h=topic/dma-fix

Any review and comments would be appreciated.


Thanks in advance,

Takashi


[PATCH] mips: implement dma_mmap_coherent()

A lazy version of dma_mmap_coherent() implementation for MIPS.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
index 891312f..723dd64 100644
--- a/arch/mips/mm/dma-default.c
+++ b/arch/mips/mm/dma-default.c
@@ -387,3 +387,15 @@ void dma_cache_sync(struct device *dev, void *vaddr, 
size_t size,
 }
 
 EXPORT_SYMBOL(dma_cache_sync);
+
+int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
+                     void *cpu_addr, dma_addr_t handle, size_t size)
+{
+       struct page *pg;
+       cpu_addr = (void *)dma_addr_to_virt(handle);
+       pg = virt_to_page(cpu_addr);
+       return remap_pfn_range(vma, vma->vm_start,
+                              page_to_pfn(pg) + vma->vm_pgoff,
+                              size, vma->vm_page_prot);
+}
+EXPORT_SYMBOL(dma_mmap_coherent);
diff --git a/include/asm-mips/dma-mapping.h b/include/asm-mips/dma-mapping.h
index c64afb4..ab12cd4 100644
--- a/include/asm-mips/dma-mapping.h
+++ b/include/asm-mips/dma-mapping.h
@@ -68,6 +68,9 @@ extern int dma_is_consistent(struct device *dev, dma_addr_t 
dma_addr);
 extern void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
               enum dma_data_direction direction);
 
+extern int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
+                            void *cpu_addr, dma_addr_t handle, size_t size);
+
 #if 0
 #define ARCH_HAS_DMA_DECLARE_COHERENT_MEMORY