dma-debug: don't enforce dma mapping check on noncoherent allocations

As discussed in [1], there is no need to enforce dma mapping check on
noncoherent allocations, a simple test on the returned CPU address is
good enough.

Add a new pair of debug helpers and use them for noncoherent alloc/free
to fix this issue.

Fixes: efa70f2 ("dma-mapping: add a new dma_alloc_pages API")
Link: https://lore.kernel.org/all/[email protected] # 1
Signed-off-by: Baochen Qiang <[email protected]>
Signed-off-by: Marek Szyprowski <[email protected]>
Link: https://lore.kernel.org/r/20250828-dma-debug-fix-noncoherent-dma-check-v1-1-76e9be0dd7fc@oss.qualcomm.com

Author: Baochen Qiang

kernel/dma/debug.c

@@ -39,6 +39,7 @@ enum {
 	dma_debug_sg,
 	dma_debug_coherent,
 	dma_debug_resource,
+	dma_debug_noncoherent,
 };
 
 enum map_err_types {
@@ -141,6 +142,7 @@ static const char *type2name[] = {
 	[dma_debug_sg] = "scatter-gather",
 	[dma_debug_coherent] = "coherent",
 	[dma_debug_resource] = "resource",
+	[dma_debug_noncoherent] = "noncoherent",
 };
 
 static const char *dir2name[] = {
@@ -993,7 +995,8 @@ static void check_unmap(struct dma_debug_entry *ref)
 			   "[mapped as %s] [unmapped as %s]\n",
 			   ref->dev_addr, ref->size,
 			   type2name[entry->type], type2name[ref->type]);
-	} else if (entry->type == dma_debug_coherent &&
+	} else if ((entry->type == dma_debug_coherent ||
+		    entry->type == dma_debug_noncoherent) &&
 		   ref->paddr != entry->paddr) {
 		err_printk(ref->dev, entry, "device driver frees "
 			   "DMA memory with different CPU address "
@@ -1581,6 +1584,49 @@ void debug_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
 	}
 }
 
+void debug_dma_alloc_pages(struct device *dev, struct page *page,
+			   size_t size, int direction,
+			   dma_addr_t dma_addr,
+			   unsigned long attrs)
+{
+	struct dma_debug_entry *entry;
+
+	if (unlikely(dma_debug_disabled()))
+		return;
+
+	entry = dma_entry_alloc();
+	if (!entry)
+		return;
+
+	entry->type      = dma_debug_noncoherent;
+	entry->dev       = dev;
+	entry->paddr	 = page_to_phys(page);
+	entry->size      = size;
+	entry->dev_addr  = dma_addr;
+	entry->direction = direction;
+
+	add_dma_entry(entry, attrs);
+}
+
+void debug_dma_free_pages(struct device *dev, struct page *page,
+			  size_t size, int direction,
+			  dma_addr_t dma_addr)
+{
+	struct dma_debug_entry ref = {
+		.type           = dma_debug_noncoherent,
+		.dev            = dev,
+		.paddr		= page_to_phys(page),
+		.dev_addr       = dma_addr,
+		.size           = size,
+		.direction      = direction,
+	};
+
+	if (unlikely(dma_debug_disabled()))
+		return;
+
+	check_unmap(&ref);
+}
+
 static int __init dma_debug_driver_setup(char *str)
 {
 	int i;

kernel/dma/debug.h

@@ -54,6 +54,13 @@ extern void debug_dma_sync_sg_for_cpu(struct device *dev,
 extern void debug_dma_sync_sg_for_device(struct device *dev,
 					 struct scatterlist *sg,
 					 int nelems, int direction);
+extern void debug_dma_alloc_pages(struct device *dev, struct page *page,
+				  size_t size, int direction,
+				  dma_addr_t dma_addr,
+				  unsigned long attrs);
+extern void debug_dma_free_pages(struct device *dev, struct page *page,
+				 size_t size, int direction,
+				 dma_addr_t dma_addr);
 #else /* CONFIG_DMA_API_DEBUG */
 static inline void debug_dma_map_page(struct device *dev, struct page *page,
 				      size_t offset, size_t size,
@@ -126,5 +133,18 @@ static inline void debug_dma_sync_sg_for_device(struct device *dev,
 						int nelems, int direction)
 {
 }
+
+static inline void debug_dma_alloc_pages(struct device *dev, struct page *page,
+					 size_t size, int direction,
+					 dma_addr_t dma_addr,
+					 unsigned long attrs)
+{
+}
+
+static inline void debug_dma_free_pages(struct device *dev, struct page *page,
+					size_t size, int direction,
+					dma_addr_t dma_addr)
+{
+}
 #endif /* CONFIG_DMA_API_DEBUG */
 #endif /* _KERNEL_DMA_DEBUG_H */

kernel/dma/mapping.c

@@ -712,7 +712,7 @@ struct page *dma_alloc_pages(struct device *dev, size_t size,
 	if (page) {
 		trace_dma_alloc_pages(dev, page_to_virt(page), *dma_handle,
 				      size, dir, gfp, 0);
-		debug_dma_map_page(dev, page, 0, size, dir, *dma_handle, 0);
+		debug_dma_alloc_pages(dev, page, size, dir, *dma_handle, 0);
 	} else {
 		trace_dma_alloc_pages(dev, NULL, 0, size, dir, gfp, 0);
 	}
@@ -738,7 +738,7 @@ void dma_free_pages(struct device *dev, size_t size, struct page *page,
 		dma_addr_t dma_handle, enum dma_data_direction dir)
 {
 	trace_dma_free_pages(dev, page_to_virt(page), dma_handle, size, dir, 0);
-	debug_dma_unmap_page(dev, dma_handle, size, dir);
+	debug_dma_free_pages(dev, page, size, dir, dma_handle);
 	__dma_free_pages(dev, size, page, dma_handle, dir);
 }
 EXPORT_SYMBOL_GPL(dma_free_pages);