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Subject[PATCH 1/7] arm-nommu: remove the partial DMA_ATTR_NON_CONSISTENT support
Date
The arm-nommu DMA code supports DMA_ATTR_NON_CONSISTENT allocations, but
does not provide a cache_sync operation. This means any user of it
will never be able to actually transfer cache ownership and thus cause
coherency bugs.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/arm/mm/dma-mapping-nommu.c | 24 +++---------------------
1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c
index f304b10e23a4..bc003df45546 100644
--- a/arch/arm/mm/dma-mapping-nommu.c
+++ b/arch/arm/mm/dma-mapping-nommu.c
@@ -39,18 +39,7 @@ static void *arm_nommu_dma_alloc(struct device *dev, size_t size,
unsigned long attrs)

{
- void *ret;
-
- /*
- * Try generic allocator first if we are advertised that
- * consistency is not required.
- */
-
- if (attrs & DMA_ATTR_NON_CONSISTENT)
- return dma_direct_alloc_pages(dev, size, dma_handle, gfp,
- attrs);
-
- ret = dma_alloc_from_global_coherent(size, dma_handle);
+ void *ret = dma_alloc_from_global_coherent(size, dma_handle);

/*
* dma_alloc_from_global_coherent() may fail because:
@@ -70,16 +59,9 @@ static void arm_nommu_dma_free(struct device *dev, size_t size,
void *cpu_addr, dma_addr_t dma_addr,
unsigned long attrs)
{
- if (attrs & DMA_ATTR_NON_CONSISTENT) {
- dma_direct_free_pages(dev, size, cpu_addr, dma_addr, attrs);
- } else {
- int ret = dma_release_from_global_coherent(get_order(size),
- cpu_addr);
-
- WARN_ON_ONCE(ret == 0);
- }
+ int ret = dma_release_from_global_coherent(get_order(size), cpu_addr);

- return;
+ WARN_ON_ONCE(ret == 0);
}

static int arm_nommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
--
2.20.1
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