From a86d10942db2e0099a369b367fe62898f95987a8 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 21 Oct 2021 09:47:31 +0200 Subject: [PATCH] dma-direct: refactor the !coherent checks in dma_direct_alloc Add a big central !dev_is_dma_coherent(dev) block to deal with as much as of the uncached allocation schemes and document the schemes a bit better. Signed-off-by: Christoph Hellwig Reviewed-by: Robin Murphy --- kernel/dma/direct.c | 66 ++++++++++++++++++++++++++++----------------- 1 file changed, 41 insertions(+), 25 deletions(-) diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index 01104660ec43..f9658fe18498 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -201,29 +201,49 @@ void *dma_direct_alloc(struct device *dev, size_t size, !force_dma_unencrypted(dev) && !is_swiotlb_for_alloc(dev)) return dma_direct_alloc_no_mapping(dev, size, dma_handle, gfp); - if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) && - !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && - !IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) && - !dev_is_dma_coherent(dev) && - !is_swiotlb_for_alloc(dev)) - return arch_dma_alloc(dev, size, dma_handle, gfp, attrs); + if (!dev_is_dma_coherent(dev)) { + /* + * Fallback to the arch handler if it exists. This should + * eventually go away. + */ + if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) && + !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && + !IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) && + !is_swiotlb_for_alloc(dev)) + return arch_dma_alloc(dev, size, dma_handle, gfp, + attrs); - if (IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) && - !dev_is_dma_coherent(dev)) - return dma_alloc_from_global_coherent(dev, size, dma_handle); + /* + * If there is a global pool, always allocate from it for + * non-coherent devices. + */ + if (IS_ENABLED(CONFIG_DMA_GLOBAL_POOL)) + return dma_alloc_from_global_coherent(dev, size, + dma_handle); + + /* + * Otherwise remap if the architecture is asking for it. But + * given that remapping memory is a blocking operation we'll + * instead have to dip into the atomic pools. + */ + remap = IS_ENABLED(CONFIG_DMA_DIRECT_REMAP); + if (remap) { + if (!gfpflags_allow_blocking(gfp) && + !is_swiotlb_for_alloc(dev)) + return dma_direct_alloc_from_pool(dev, size, + dma_handle, gfp); + } else { + if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED)) + set_uncached = true; + } + } /* - * Remapping or decrypting memory may block. If either is required and - * we can't block, allocate the memory from the atomic pools. - * If restricted DMA (i.e., is_swiotlb_for_alloc) is required, one must - * set up another device coherent pool by shared-dma-pool and use - * dma_alloc_from_dev_coherent instead. + * Decrypting memory may block, so allocate the memory from the atomic + * pools if we can't block. */ if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) && - !gfpflags_allow_blocking(gfp) && - (force_dma_unencrypted(dev) || - (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && - !dev_is_dma_coherent(dev))) && + force_dma_unencrypted(dev) && !gfpflags_allow_blocking(gfp) && !is_swiotlb_for_alloc(dev)) return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); @@ -231,10 +251,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO); if (!page) return NULL; - - if (!dev_is_dma_coherent(dev) && IS_ENABLED(CONFIG_DMA_DIRECT_REMAP)) { - remap = true; - } else if (PageHighMem(page)) { + if (PageHighMem(page)) { /* * Depending on the cma= arguments and per-arch setup, * dma_alloc_contiguous could return highmem pages. @@ -246,9 +263,8 @@ void *dma_direct_alloc(struct device *dev, size_t size, goto out_free_pages; } remap = true; - } else if (!dev_is_dma_coherent(dev) && - IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED)) - set_uncached = true; + set_uncached = false; + } if (remap) { /* remove any dirty cache lines on the kernel alias */ -- 2.25.1