Commit e7793e53 authored by Mike Rapoport's avatar Mike Rapoport Committed by Linus Torvalds
Browse files

arc: update comment about HIGHMEM implementation 

Arc does not use DISCONTIGMEM to implement high memory, update the comment
describing how high memory works to reflect this.

Link: https://lkml.kernel.org/r/20210608091316.3622-3-rppt@kernel.org


Signed-off-by: default avatarMike Rapoport <rppt@linux.ibm.com>
Acked-by: default avatarVineet Gupta <vgupta@synopsys.com>
Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fdb7d9b7

arch/arc/mm/init.c

+5 −8
Original line number Diff line number Diff line
@@ -139,16 +139,13 @@ void __init setup_arch_memory(void) 


#ifdef CONFIG_HIGHMEM

	/*

	 * Populate a new node with highmem

	 *

	 * On ARC (w/o PAE) HIGHMEM addresses are actually smaller (0 based)

	 * than addresses in normal ala low memory (0x8000_0000 based).

	 * than addresses in normal aka low memory (0x8000_0000 based).

	 * Even with PAE, the huge peripheral space hole would waste a lot of

	 * mem with single mem_map[]. This warrants a mem_map per region design.

	 * Thus HIGHMEM on ARC is imlemented with DISCONTIGMEM.

	 *

	 * DISCONTIGMEM in turns requires multiple nodes. node 0 above is

	 * populated with normal memory zone while node 1 only has highmem

	 * mem with single contiguous mem_map[].

	 * Thus when HIGHMEM on ARC is enabled the memory map corresponding

	 * to the hole is freed and ARC specific version of pfn_valid()

	 * handles the hole in the memory map.

	 */

#ifdef CONFIG_DISCONTIGMEM

	node_set_online(1);