linux-kernel - [PATCH 2/7] arc: remove the partial DMA_ATTR_NON

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Date:   Fri, 14 Jun 2019 16:44:26 +0200
From:   Christoph Hellwig <hch@....de>
To:     Vineet Gupta <vgupta@...opsys.com>
Cc:     Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        Helge Deller <deller@....de>,
        Vladimir Murzin <vladimir.murzin@....com>,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        openrisc@...ts.librecores.org, linux-parisc@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/7] 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@....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