[PATCH v4 02/15] dma: Allow dma_get_cache_alignment() to return the smaller cache_line_size()

[Catalin Marinas]

On architectures like arm64, ARCH_DMA_MINALIGN is larger than most cache
line size configurations deployed. However, the single kernel binary
requirement doesn't allow the smaller ARCH_DMA_MINALIGN. Permit an
architecture to opt in to dma_get_cache_alignment() returning
cache_line_size() which can be probed at run-time.

Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Robin Murphy <robin.murphy at arm.com>
Cc: Will Deacon <will at kernel.org>
---
 include/linux/dma-mapping.h | 2 ++
 kernel/dma/Kconfig          | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 3288a1339271..b29124341317 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -545,6 +545,8 @@ static inline int dma_set_min_align_mask(struct device *dev,
 
 static inline int dma_get_cache_alignment(void)
 {
+	if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CACHE_LINE_SIZE))
+		return cache_line_size();
 #ifdef ARCH_HAS_DMA_MINALIGN
 	return ARCH_DMA_MINALIGN;
 #endif
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 6677d0e64d27..cc750062c412 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -76,6 +76,13 @@ config ARCH_HAS_DMA_PREP_COHERENT
 config ARCH_HAS_FORCE_DMA_UNENCRYPTED
 	bool
 
+config ARCH_HAS_DMA_CACHE_LINE_SIZE
+	bool
+	help
+	  Select if the architecture has non-coherent DMA and
+	  defines ARCH_DMA_MINALIGN larger than a run-time
+	  cache_line_size().
+
 #
 # Select this option if the architecture assumes DMA devices are coherent
 # by default.