On 6/15/20 8:05 AM, Christoph Hellwig wrote:
> 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 <h...@lst.de>
> Reported-by: dillon min <dillon.min...@gmail.com>
> Reviewed-by: Vladimir Murzin <vladimir.mur...@arm.com>
> Tested-by: dillon min <dillon.min...@gmail.com>
> ---
> kernel/dma/Kconfig | 1 +
> kernel/dma/direct.c | 14 --------------
> 2 files changed, 1 insertion(+), 14 deletions(-)
>
> diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
> index d006668c0027d2..e0dae570a51530 100644
> --- 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_REMAP
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 0a4881e59aa7d6..9ec6a5c3fc578c 100644
> --- 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)
> {
>
LGTM. Should it go stable as well?
Cheers
Vladimir
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