csky: simplify detection of memory zone boundaries

The free_area_init() function 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/20200412194859.12663-10-rppt@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/csky/kernel/setup.c

@@ -26,7 +26,9 @@ struct screen_info screen_info = {
 
 static void __init csky_memblock_init(void)
 {
-	unsigned long zone_size[MAX_NR_ZONES];
+	unsigned long lowmem_size = PFN_DOWN(LOWMEM_LIMIT - PHYS_OFFSET_OFFSET);
+	unsigned long sseg_size = PFN_DOWN(SSEG_SIZE - PHYS_OFFSET_OFFSET);
+	unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0 };
 	signed long size;
 
 	memblock_reserve(__pa(_stext), _end - _stext);
@@ -36,28 +38,22 @@ static void __init csky_memblock_init(void)
 
 	memblock_dump_all();
 
-	memset(zone_size, 0, sizeof(zone_size));
-
 	min_low_pfn = PFN_UP(memblock_start_of_DRAM());
 	max_low_pfn = max_pfn = PFN_DOWN(memblock_end_of_DRAM());
 
 	size = max_pfn - min_low_pfn;
 
-	if (size <= PFN_DOWN(SSEG_SIZE - PHYS_OFFSET_OFFSET))
-		zone_size[ZONE_NORMAL] = size;
-	else if (size < PFN_DOWN(LOWMEM_LIMIT - PHYS_OFFSET_OFFSET)) {
-		zone_size[ZONE_NORMAL] =
-				PFN_DOWN(SSEG_SIZE - PHYS_OFFSET_OFFSET);
-		max_low_pfn = min_low_pfn + zone_size[ZONE_NORMAL];
-	} else {
-		zone_size[ZONE_NORMAL] =
-				PFN_DOWN(LOWMEM_LIMIT - PHYS_OFFSET_OFFSET);
-		max_low_pfn = min_low_pfn + zone_size[ZONE_NORMAL];
+	if (size >= lowmem_size) {
+		max_low_pfn = min_low_pfn + lowmem_size;
 		write_mmu_msa1(read_mmu_msa0() + SSEG_SIZE);
+	} else if (size > sseg_size) {
+		max_low_pfn = min_low_pfn + sseg_size;
 	}
 
+	max_zone_pfn[ZONE_NORMAL] = max_low_pfn;
+
 #ifdef CONFIG_HIGHMEM
-	zone_size[ZONE_HIGHMEM] = max_pfn - max_low_pfn;
+	max_zone_pfn[ZONE_HIGHMEM] = max_pfn;
 
 	highstart_pfn = max_low_pfn;
 	highend_pfn   = max_pfn;
@@ -66,7 +62,7 @@ static void __init csky_memblock_init(void)
 
 	dma_contiguous_reserve(0);
 
-	free_area_init_node(0, zone_size, min_low_pfn, NULL);
+	free_area_init(max_zone_pfn);
 }
 
 void __init setup_arch(char **cmdline_p)