arc: remove the partial DMA_ATTR_NON_CONSISTENT support

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>
Reviewed-by: Evgeniy Paltsev <paltsev@synopsys.com>
Tested-by: Evgeniy Paltsev <paltsev@synopsys.com>

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
@@ -46,15 +45,11 @@ 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;
-	}
 
 	/*
 	 * Evict any existing L1 and/or L2 lines for the backing page
@@ -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);
-
 	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);
-
 	__free_pages(page, get_order(size));
 }