dma-direct: re-enable mmap for !CONFIG_MMU

nommu configfs can trivially map the coherent allocations to user space,
as no actual page table setup is required and the kernel and the user
space programs share the same address space.

Fixes: 62fcee9a3bd7 ("dma-mapping: remove CONFIG_ARCH_NO_COHERENT_DMA_MMAP")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: dillon min <dillon.minfei@gmail.com>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: dillon min <dillon.minfei@gmail.com>

diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index a0ce3c1494fdd2c37e092e7eb17ef6f6a96a65db..14ef8e1bdefe806c880ae0e3e7085cede08a1c61 100644 (file)
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -71,6 +71,7 @@ config SWIOTLB
 # in the pagetables
 #
 config DMA_NONCOHERENT_MMAP
+       default y if !MMU
        bool
 
 config DMA_COHERENT_POOL

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 0a4881e59aa7d68ab8e335387a30e8b2a03d290b..9ec6a5c3fc578c091c7a31d882cd127c17617bc1 100644 (file)
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -459,7 +459,6 @@ int dma_direct_get_sgtable(struct device *dev, struct sg_table *sgt,
        return ret;
 }
 
-#ifdef CONFIG_MMU
 bool dma_direct_can_mmap(struct device *dev)
 {
        return dev_is_dma_coherent(dev) ||
@@ -485,19 +484,6 @@ int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
        return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
                        user_count << PAGE_SHIFT, vma->vm_page_prot);
 }
-#else /* CONFIG_MMU */
-bool dma_direct_can_mmap(struct device *dev)
-{
-       return false;
-}
-
-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)
-{
-       return -ENXIO;
-}
-#endif /* CONFIG_MMU */
 
 int dma_direct_supported(struct device *dev, u64 mask)
 {