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Subject[PATCH 4/7] dma-mapping: add a dma_alloc_need_uncached helper
Date
Check if we need to allocate uncached memory for a device given the
allocation flags. Switch over the uncached segment check to this helper
to deal with architectures that do not support the dma_cache_sync
operation and thus should not returned cacheable memory for
DMA_ATTR_NON_CONSISTENT allocations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
include/linux/dma-noncoherent.h | 14 ++++++++++++++
kernel/dma/direct.c | 4 ++--
2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/linux/dma-noncoherent.h b/include/linux/dma-noncoherent.h
index 7e0126a04e02..732919ac5c11 100644
--- a/include/linux/dma-noncoherent.h
+++ b/include/linux/dma-noncoherent.h
@@ -20,6 +20,20 @@ static inline bool dev_is_dma_coherent(struct device *dev)
}
#endif /* CONFIG_ARCH_HAS_DMA_COHERENCE_H */

+/*
+ * Check if an allocation needs to be marked uncached to be coherent.
+ */
+static inline bool dma_alloc_need_uncached(struct device *dev,
+ unsigned long attrs)
+{
+ if (dev_is_dma_coherent(dev))
+ return false;
+ if (IS_ENABLED(CONFIG_DMA_NONCOHERENT_CACHE_SYNC) &&
+ (attrs & DMA_ATTR_NON_CONSISTENT))
+ return false;
+ return true;
+}
+
void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
gfp_t gfp, unsigned long attrs);
void arch_dma_free(struct device *dev, size_t size, void *cpu_addr,
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index b67f0aa08aa3..c2893713bf80 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -160,7 +160,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
memset(ret, 0, size);

if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
- !dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_NON_CONSISTENT)) {
+ dma_alloc_need_uncached(dev, attrs)) {
arch_dma_prep_coherent(page, size);
ret = uncached_kernel_address(ret);
}
@@ -182,7 +182,7 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
set_memory_encrypted((unsigned long)cpu_addr, 1 << page_order);

if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
- !dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_NON_CONSISTENT))
+ dma_alloc_need_uncached(dev, attrs))
cpu_addr = cached_kernel_address(cpu_addr);
__dma_direct_free_pages(dev, size, virt_to_page(cpu_addr));
}
--
2.20.1
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