Subject: [PATCH v3 15/29] powerpc: introduce arch_zone_limits_init()

From: Mike Rapoport <[email-masked]>
Date: Sun, 11 Jan 2026 10:20:49 +0200

From: "Mike Rapoport (Microsoft)" <[email-masked]>

Move calculations of zone limits to a dedicated arch_zone_limits_init()
function.

Later MM core will use this function as an architecture specific callback
during nodes and zones initialization and thus there won't be a need to
call free_area_init() from every architecture.

Signed-off-by: Mike Rapoport (Microsoft) <[email-masked]>
---
 arch/powerpc/mm/mem.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 3ddbfdbfa941..03c05ec56041 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -221,13 +221,23 @@ static int __init mark_nonram_nosave(void)
  * anyway) will take a first dip into ZONE_NORMAL and get otherwise served by
  * ZONE_DMA.
  */
-static unsigned long max_zone_pfns[MAX_NR_ZONES];
+void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
+{
+#ifdef CONFIG_ZONE_DMA
+	max_zone_pfns[ZONE_DMA] = min((zone_dma_limit >> PAGE_SHIFT) + 1, max_low_pfn);
+#endif
+	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
+#ifdef CONFIG_HIGHMEM
+	max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
+#endif
+}
 
 /*
  * paging_init() sets up the page tables - in fact we've already done this.
  */
 void __init paging_init(void)
 {
+	unsigned long max_zone_pfns[MAX_NR_ZONES] = { 0 };
 	unsigned long long total_ram = memblock_phys_mem_size();
 	phys_addr_t top_of_ram = memblock_end_of_DRAM();
 	int zone_dma_bits;
@@ -259,15 +269,7 @@ void __init paging_init(void)
 
 	zone_dma_limit = DMA_BIT_MASK(zone_dma_bits);
 
-#ifdef CONFIG_ZONE_DMA
-	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn,
-				      1UL << (zone_dma_bits - PAGE_SHIFT));
-#endif
-	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
-#ifdef CONFIG_HIGHMEM
-	max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
-#endif
-
+	arch_zone_limits_init(max_zone_pfns);
 	free_area_init(max_zone_pfns);
 
 	mark_nonram_nosave();
-- 
2.51.0