[PATCH] arm64: mm: make CONFIG_ZONE_DMA32 configurable

[Miles Chen]

This change makes CONFIG_ZONE_DMA32 defuly y and allows users
to overwrite it.

For the SoCs that do not need CONFIG_ZONE_DMA32, this is the
first step to manage all available memory by a single
zone(normal zone) to reduce the overhead of multiple zones.

The change also fixes a build error when CONFIG_NUMA=y and
CONFIG_ZONE_DMA32=n.

arch/arm64/mm/init.c:195:17: error: use of undeclared identifier 'ZONE_DMA32'
                max_zone_pfns[ZONE_DMA32] = PFN_DOWN(max_zone_dma_phys());

Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx>
---
 arch/arm64/Kconfig   | 3 ++-
 arch/arm64/mm/init.c | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 76f6e4765f49..9d20a736d1d1 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -260,7 +260,8 @@ config GENERIC_CALIBRATE_DELAY
 	def_bool y
 
 config ZONE_DMA32
-	def_bool y
+	bool "Support DMA32 zone"
+	default y
 
 config HAVE_GENERIC_GUP
 	def_bool y
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index d2adffb81b5d..96829ce21f99 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -191,8 +191,10 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
 
+#ifdef CONFIG_ZONE_DMA32
 	if (IS_ENABLED(CONFIG_ZONE_DMA32))
 		max_zone_pfns[ZONE_DMA32] = PFN_DOWN(max_zone_dma_phys());
+#endif
 	max_zone_pfns[ZONE_NORMAL] = max;
 
 	free_area_init_nodes(max_zone_pfns);
-- 
2.18.0