ARM/dma-mapping: remove get_coherent_dma_mask

The core DMA code already checks for valid DMA masks earlier on, and
doesn't allow NULL struct device pointers.  Remove the now not required
checks.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

arch/arm/mm/dma-mapping.c

@@ -219,7 +219,7 @@ const struct dma_map_ops arm_coherent_dma_ops = {
 };
 EXPORT_SYMBOL(arm_coherent_dma_ops);
 
-static int __dma_supported(struct device *dev, u64 mask, bool warn)
+static int __dma_supported(struct device *dev, u64 mask)
 {
 	unsigned long max_dma_pfn = min(max_pfn - 1, arm_dma_pfn_limit);
 
@@ -227,41 +227,11 @@ static int __dma_supported(struct device *dev, u64 mask, bool warn)
 	 * Translate the device's DMA mask to a PFN limit.  This
 	 * PFN number includes the page which we can DMA to.
 	 */
-	if (dma_to_pfn(dev, mask) < max_dma_pfn) {
-		if (warn)
-			dev_warn(dev, "Coherent DMA mask %#llx (pfn %#lx-%#lx) covers a smaller range of system memory than the DMA zone pfn 0x0-%#lx\n",
-				 mask,
-				 dma_to_pfn(dev, 0), dma_to_pfn(dev, mask) + 1,
-				 max_dma_pfn + 1);
+	if (dma_to_pfn(dev, mask) < max_dma_pfn)
 		return 0;
-	}
-
 	return 1;
 }
 
-static u64 get_coherent_dma_mask(struct device *dev)
-{
-	u64 mask = (u64)DMA_BIT_MASK(32);
-
-	if (dev) {
-		mask = dev->coherent_dma_mask;
-
-		/*
-		 * Sanity check the DMA mask - it must be non-zero, and
-		 * must be able to be satisfied by a DMA allocation.
-		 */
-		if (mask == 0) {
-			dev_warn(dev, "coherent DMA mask is unset\n");
-			return 0;
-		}
-
-		if (!__dma_supported(dev, mask, true))
-			return 0;
-	}
-
-	return mask;
-}
-
 static void __dma_clear_buffer(struct page *page, size_t size, int coherent_flag)
 {
 	/*
@@ -688,7 +658,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 			 gfp_t gfp, pgprot_t prot, bool is_coherent,
 			 unsigned long attrs, const void *caller)
 {
-	u64 mask = get_coherent_dma_mask(dev);
+	u64 mask = dev->coherent_dma_mask;
 	struct page *page = NULL;
 	void *addr;
 	bool allowblock, cma;
@@ -712,9 +682,6 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 	}
 #endif
 
-	if (!mask)
-		return NULL;
-
 	buf = kzalloc(sizeof(*buf),
 		      gfp & ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM));
 	if (!buf)
@@ -1095,7 +1062,7 @@ void arm_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
  */
 int arm_dma_supported(struct device *dev, u64 mask)
 {
-	return __dma_supported(dev, mask, false);
+	return __dma_supported(dev, mask);
 }
 
 static const struct dma_map_ops *arm_get_dma_map_ops(bool coherent)