Hi, Christoph, Maybe you missed something. 1, pool_alloc_page() use dma_alloc_coherent() to allocate pool pages, and of course these pages are aligned to ARCH_DMA_MINALIGN. 2, dma_pool_alloc() is the element allocator, but it doesn't use dma_alloc_coherent(). Elements only align to pool->size, but pool->size is usually less than ARCH_DMA_MINALIGN. 3, ARCH_DMA_MINALIGN is now only used in serveral drivers, no dma_ops use it.
Huacai ------------------ Original ------------------ From: "Christoph Hellwig"<[email protected]>; Date: Mon, Sep 18, 2017 01:22 PM To: "Huacai Chen"<[email protected]>; Cc: "Andrew Morton"<[email protected]>; "Fuxin Zhang"<[email protected]>; "linux-mm"<[email protected]>; "linux-kernel"<[email protected]>; "stable"<[email protected]>; Subject: Re: [PATCH V5 2/3] mm: dmapool: Align to ARCH_DMA_MINALIGN innon-coherent DMA mode The dmapool code uses dma_alloc_coherent to allocate each element, and dma_alloc_coherent must align to ARCH_DMA_MINALIGN already. If you implementation doesn't do that it needs to be fixed.
