[PATCH v4 15/15] arm64: Enable ARCH_WANT_KMALLOC_DMA_BOUNCE for arm64

[Catalin Marinas]

With the DMA bouncing of unaligned kmalloc() buffers now in place,
enable it for arm64 to allow the kmalloc-{8,16,32,48,96} caches. In
addition, always create the swiotlb buffer even when the end of RAM is
within the 32-bit physical address range (the swiotlb buffer can still
be disabled on the kernel command line).

Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
---
 arch/arm64/Kconfig   | 1 +
 arch/arm64/mm/init.c | 7 ++++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index d11340b41703..1dcfa78f131f 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -102,6 +102,7 @@ config ARM64
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)
+	select ARCH_WANT_KMALLOC_DMA_BOUNCE
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 66e70ca47680..3ac2e9d79ce4 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -442,7 +442,12 @@ void __init bootmem_init(void)
  */
 void __init mem_init(void)
 {
-	swiotlb_init(max_pfn > PFN_DOWN(arm64_dma_phys_limit), SWIOTLB_VERBOSE);
+	bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);
+
+	if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC))
+		swiotlb = true;
+
+	swiotlb_init(swiotlb, SWIOTLB_VERBOSE);
 
 	/* this will put all unused low memory onto the freelists */
 	memblock_free_all();