powerpc: Implement dma_mmap_coherent()

This is used by Alsa to mmap buffers allocated with dma_alloc_coherent()
into userspace. We need a special variant to handle machines with
non-coherent DMAs as those buffers have "special" virt addresses and
require non-cachable mappings

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/dma.c b/arch/powerpc/kernel/dma.c
index cf02cad62d9a..d238c082c3c5 100644
--- a/arch/powerpc/kernel/dma.c
+++ b/arch/powerpc/kernel/dma.c
@@ -179,3 +179,21 @@ static int __init dma_init(void)
        return 0;
 }
 fs_initcall(dma_init);
+
+int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
+                      void *cpu_addr, dma_addr_t handle, size_t size)
+{
+        unsigned long pfn;
+
+#ifdef CONFIG_NOT_COHERENT_CACHE
+        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+        pfn = __dma_get_coherent_pfn((unsigned long)cpu_addr);
+#else
+        pfn = page_to_pfn(virt_to_page(cpu_addr));
+#endif
+        return remap_pfn_range(vma, vma->vm_start,
+                               pfn + vma->vm_pgoff,
+                               vma->vm_end - vma->vm_start,
+                               vma->vm_page_prot);
+}
+EXPORT_SYMBOL_GPL(dma_mmap_coherent);