MIPS: Fix `dma_alloc_coherent' returning a non-coherent allocation

Maciej W. Rozycki · paulburton · commit d01501f85249 · 2018-11-05T10:08:13.000-08:00
Fix a MIPS `dma_alloc_coherent' regression from commit bc3ec75 ("dma-mapping: merge direct and noncoherent ops") that causes a cached allocation to be returned on noncoherent cache systems. This is due to an inverted check now used in the MIPS implementation of `arch_dma_alloc' on the result from `dma_direct_alloc_pages' before doing the cached-to-uncached mapping of the allocation address obtained. The mapping has to be done for a non-NULL rather than NULL result, because a NULL result means the allocation has failed. Invert the check for correct operation then. Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org> Signed-off-by: Paul Burton <paul.burton@mips.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Fixes: bc3ec75 ("dma-mapping: merge direct and noncoherent ops") Patchwork: https://patchwork.linux-mips.org/patch/20965/
diff --git a/arch/mips/mm/dma-noncoherent.c b/arch/mips/mm/dma-noncoherent.c
@@ -50,7 +50,7 @@ void *arch_dma_alloc(struct device *dev, size_t size,
 	void *ret;
 
 	ret = dma_direct_alloc_pages(dev, size, dma_handle, gfp, attrs);
-	if (!ret && !(attrs & DMA_ATTR_NON_CONSISTENT)) {
+	if (ret && !(attrs & DMA_ATTR_NON_CONSISTENT)) {
 		dma_cache_wback_inv((unsigned long) ret, size);
 		ret = (void *)UNCAC_ADDR(ret);
 	}

Original file line number	Diff line number	Diff line change
`@@ -50,7 +50,7 @@ void arch_dma_alloc(struct device dev, size_t size,`
`50`	`50`	`void *ret;`
`51`	`51`
`52`	`52`	`ret = dma_direct_alloc_pages(dev, size, dma_handle, gfp, attrs);`
`53`		`- if (!ret && !(attrs & DMA_ATTR_NON_CONSISTENT)) {`
	`53`	`+ if (ret && !(attrs & DMA_ATTR_NON_CONSISTENT)) {`
`54`	`54`	`dma_cache_wback_inv((unsigned long) ret, size);`
`55`	`55`	`ret = (void *)UNCAC_ADDR(ret);`
`56`	`56`	`}`