From c44094eee32f32f175aadc0efcac449d99b1bbf7 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 23 Aug 2022 13:21:11 +0100 Subject: arm64: dma: Drop cache invalidation from arch_dma_prep_coherent() arch_dma_prep_coherent() is called when preparing a non-cacheable region for a consistent DMA buffer allocation. Since the buffer pages may previously have been written via a cacheable mapping and consequently allocated as dirty cachelines, the purpose of this function is to remove these dirty lines from the cache, writing them back so that the non-coherent device is able to see them. On arm64, this operation can be achieved with a clean to the point of coherency; a subsequent invalidation is not required and serves little purpose in the presence of a cacheable alias (e.g. the linear map), since clean lines can be speculatively fetched back into the cache after the invalidation operation has completed. Relax the cache maintenance in arch_dma_prep_coherent() so that only a clean, and not a clean-and-invalidate operation is performed. Cc: Mark Rutland Cc: Robin Murphy Cc: Christoph Hellwig Cc: Ard Biesheuvel Signed-off-by: Will Deacon Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20220823122111.17439-1-will@kernel.org Signed-off-by: Catalin Marinas --- arch/arm64/mm/dma-mapping.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c index 599cf81f5685..83a512a6ff0d 100644 --- a/arch/arm64/mm/dma-mapping.c +++ b/arch/arm64/mm/dma-mapping.c @@ -36,7 +36,7 @@ void arch_dma_prep_coherent(struct page *page, size_t size) { unsigned long start = (unsigned long)page_address(page); - dcache_clean_inval_poc(start, start + size); + dcache_clean_poc(start, start + size); } #ifdef CONFIG_IOMMU_DMA -- cgit v1.2.1