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Subject[PATCH 2/7] arc: remove the partial DMA_ATTR_NON_CONSISTENT support
Date
The arc 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/arc/mm/dma.c | 21 ++++++---------------
1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index 1525ac00fd02..9832928f896d 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -24,7 +24,6 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
struct page *page;
phys_addr_t paddr;
void *kvaddr;
- bool need_coh = !(attrs & DMA_ATTR_NON_CONSISTENT);

/*
* __GFP_HIGHMEM flag is cleared by upper layer functions
@@ -46,14 +45,10 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
* A coherent buffer needs MMU mapping to enforce non-cachability.
* kvaddr is kernel Virtual address (0x7000_0000 based).
*/
- if (need_coh) {
- kvaddr = ioremap_nocache(paddr, size);
- if (kvaddr == NULL) {
- __free_pages(page, order);
- return NULL;
- }
- } else {
- kvaddr = (void *)(u32)paddr;
+ kvaddr = ioremap_nocache(paddr, size);
+ if (kvaddr == NULL) {
+ __free_pages(page, order);
+ return NULL;
}

/*
@@ -66,9 +61,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
* Currently flush_cache_vmap nukes the L1 cache completely which
* will be optimized as a separate commit
*/
- if (need_coh)
- dma_cache_wback_inv(paddr, size);
-
+ dma_cache_wback_inv(paddr, size);
return kvaddr;
}

@@ -78,9 +71,7 @@ void arch_dma_free(struct device *dev, size_t size, void *vaddr,
phys_addr_t paddr = dma_handle;
struct page *page = virt_to_page(paddr);

- if (!(attrs & DMA_ATTR_NON_CONSISTENT))
- iounmap((void __force __iomem *)vaddr);
-
+ iounmap((void __force __iomem *)vaddr);
__free_pages(page, get_order(size));
}

--
2.20.1
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