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 <h...@lst.de>
---
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 01104660ec439..f9658fe18498c 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 */
--
2.30.2
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