arm: simplify detection of memory zone boundaries

free_area_init() only requires the definition of maximal PFN for each of
the supported zone rater than calculation of actual zone sizes and the
sizes of the holes between the zones.

After removal of CONFIG_HAVE_MEMBLOCK_NODE_MAP the free_area_init() is
available to all architectures.

Using this function instead of free_area_init_node() simplifies the zone
detection.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Hoan Tran <hoan@os.amperecomputing.com>	[arm64]
Cc: Baoquan He <bhe@redhat.com>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: Guo Ren <guoren@kernel.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/20200412194859.12663-8-rppt@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm/mm/init.c

@@ -92,18 +92,6 @@ EXPORT_SYMBOL(arm_dma_zone_size);
  */
 phys_addr_t arm_dma_limit;
 unsigned long arm_dma_pfn_limit;
-
-static void __init arm_adjust_dma_zone(unsigned long *size, unsigned long *hole,
-	unsigned long dma_size)
-{
-	if (size[0] <= dma_size)
-		return;
-
-	size[ZONE_NORMAL] = size[0] - dma_size;
-	size[ZONE_DMA] = dma_size;
-	hole[ZONE_NORMAL] = hole[0];
-	hole[ZONE_DMA] = 0;
-}
 #endif
 
 void __init setup_dma_zone(const struct machine_desc *mdesc)
@@ -121,56 +109,16 @@ void __init setup_dma_zone(const struct machine_desc *mdesc)
 static void __init zone_sizes_init(unsigned long min, unsigned long max_low,
 	unsigned long max_high)
 {
-	unsigned long zone_size[MAX_NR_ZONES], zhole_size[MAX_NR_ZONES];
-	struct memblock_region *reg;
-
-	/*
-	 * initialise the zones.
-	 */
-	memset(zone_size, 0, sizeof(zone_size));
+	unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0 };
 
-	/*
-	 * The memory size has already been determined.  If we need
-	 * to do anything fancy with the allocation of this memory
-	 * to the zones, now is the time to do it.
-	 */
-	zone_size[0] = max_low - min;
-#ifdef CONFIG_HIGHMEM
-	zone_size[ZONE_HIGHMEM] = max_high - max_low;
+#ifdef CONFIG_ZONE_DMA
+	max_zone_pfn[ZONE_DMA] = min(arm_dma_pfn_limit, max_low);
 #endif
-
-	/*
-	 * Calculate the size of the holes.
-	 *  holes = node_size - sum(bank_sizes)
-	 */
-	memcpy(zhole_size, zone_size, sizeof(zhole_size));
-	for_each_memblock(memory, reg) {
-		unsigned long start = memblock_region_memory_base_pfn(reg);
-		unsigned long end = memblock_region_memory_end_pfn(reg);
-
-		if (start < max_low) {
-			unsigned long low_end = min(end, max_low);
-			zhole_size[0] -= low_end - start;
-		}
+	max_zone_pfn[ZONE_NORMAL] = max_low;
 #ifdef CONFIG_HIGHMEM
-		if (end > max_low) {
-			unsigned long high_start = max(start, max_low);
-			zhole_size[ZONE_HIGHMEM] -= end - high_start;
-		}
+	max_zone_pfn[ZONE_HIGHMEM] = max_high;
 #endif
-	}
-
-#ifdef CONFIG_ZONE_DMA
-	/*
-	 * Adjust the sizes according to any special requirements for
-	 * this machine type.
-	 */
-	if (arm_dma_zone_size)
-		arm_adjust_dma_zone(zone_size, zhole_size,
-			arm_dma_zone_size >> PAGE_SHIFT);
-#endif
-
-	free_area_init_node(0, zone_size, min, zhole_size);
+	free_area_init(max_zone_pfn);
 }
 
 #ifdef CONFIG_HAVE_ARCH_PFN_VALID
@@ -306,7 +254,7 @@ void __init bootmem_init(void)
 	sparse_init();
 
 	/*
-	 * Now free the memory - free_area_init_node needs
+	 * Now free the memory - free_area_init needs
 	 * the sparse mem_map arrays initialized by sparse_init()
 	 * for memmap_init_zone(), otherwise all PFNs are invalid.
 	 */