[PATCH] dma-direct: Restore arch_dma_alloc() for the DMA_ATTR_NO_KERNEL_MAPPING case

[Marek Szyprowski]

Commit 849facea92fa ("dma-direct: simplify the DMA_ATTR_NO_KERNEL_MAPPING
handling") moved the DMA_ATTR_NO_KERNEL_MAPPING shortcut in
dma_direct_alloc() in front of the arch_dma_alloc() call. Architectures
providing their own DMA coherent allocator (CONFIG_ARCH_HAS_DMA_ALLOC)
therefore no longer see such requests. ARM 32bit is one of such. Lack of
the call to arch_dma_alloc() results in the lack of proper cache
management on HighMem pages.

Take the dma-direct shortcut only for coherent devices or when the
architecture doesn't provide arch_dma_alloc(). While touching this,
move that check into separate function to avoid duplication in alloc
and free paths.

Fixes: 849facea92fa ("dma-direct: simplify the DMA_ATTR_NO_KERNEL_MAPPING handling")
Reported-by: Aneesh Kumar K.V <aneesh.kumar at kernel.org>
Closes: https://lore.kernel.org/all/yq5ams2akznl.fsf@kernel.org/
Assisted-by: Claude Opus 5.5 <noreply at anthropic.com>
Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
---
 kernel/dma/direct.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index da665ca22d5c..a31bd3129f3f 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -179,6 +179,22 @@ static struct page *dma_direct_alloc_from_pool(struct device *dev, size_t size,
 	return page;
 }
 
+/*
+ * Check if the allocation can skip the kernel mapping and return the page
+ * pointer as the cookie.
+ */
+static bool dma_direct_use_no_mapping(struct device *dev, unsigned long attrs)
+{
+	if ((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | __DMA_ATTR_ALLOC_CC_SHARED)) !=
+	    DMA_ATTR_NO_KERNEL_MAPPING)
+		return false;
+	if (is_swiotlb_for_alloc(dev))
+		return false;
+	if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_ALLOC) && !dev_is_dma_coherent(dev))
+		return false;
+	return true;
+}
+
 static void *dma_direct_alloc_no_mapping(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, gfp_t gfp)
 {
@@ -226,8 +242,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
 	if (attrs & DMA_ATTR_NO_WARN)
 		gfp |= __GFP_NOWARN;
 
-	if (((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | __DMA_ATTR_ALLOC_CC_SHARED)) ==
-	     DMA_ATTR_NO_KERNEL_MAPPING) && !is_swiotlb_for_alloc(dev))
+	if (dma_direct_use_no_mapping(dev, attrs))
 		return dma_direct_alloc_no_mapping(dev, size, dma_handle, gfp);
 
 	if (!dev_is_dma_coherent(dev)) {
@@ -374,8 +389,7 @@ void dma_direct_free(struct device *dev, size_t size,
 	if (attrs & __DMA_ATTR_ALLOC_CC_SHARED)
 		mark_mem_encrypted = true;
 
-	if (((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | __DMA_ATTR_ALLOC_CC_SHARED)) ==
-	     DMA_ATTR_NO_KERNEL_MAPPING) && !is_swiotlb_for_alloc(dev)) {
+	if (dma_direct_use_no_mapping(dev, attrs)) {
 		/* cpu_addr is a struct page cookie, not a kernel address */
 		dma_free_contiguous(dev, cpu_addr, size);
 		return;
-- 
2.43.0