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ARC: support HIGHMEM even without PAE40 

Initial HIGHMEM support on ARC was introduced for PAE40 where the low
memory (0x8000_0000 based) and high memory (0x1_0000_0000) were
physically contiguous. So CONFIG_FLATMEM sufficed (despite a peipheral
hole in the middle, which wasted a bit of struct page memory, but things
worked).

However w/o PAE, highmem was not possible and we could only reach
~1.75GB of DDR. Now there is a use case to access ~4GB of DDR w/o PAE40
The idea is to have low memory at canonical 0x8000_0000 and highmem
at 0 so enire 4GB address space is available for physical addressing
This needs additional platform/interconnect mapping to convert
the non contiguous physical addresses into linear bus adresses.

From Linux point of view, non contiguous divide means FLATMEM no
longer works and DISCONTIGMEM is needed to track the pfns in the 2
regions.

This scheme would also work for PAE40, only better in that we don't
waste struct page memory for the peripheral hole.

The DT description will be something like

    memory {
        ...
        reg = <0x80000000 0x200000000   /* 512MB: lowmem */
               0x00000000 0x10000000>;  /* 256MB: highmem */
   }

Signed-off-by: Noam Camus <noamc@ezchip.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2016-04-18 10:49:56 +05:30
parent 2519d75367
commit 26f9d5fd82
4 changed files with 98 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
arch/arc/Kconfig
View File

@ -58,6 +58,9 @@ config GENERIC_CSUM
config RWSEM_GENERIC_SPINLOCK
def_bool y
config ARCH_DISCONTIGMEM_ENABLE
def_bool y
config ARCH_FLATMEM_ENABLE
def_bool y
@ -347,6 +350,15 @@ config ARC_HUGEPAGE_16M
endchoice
config NODES_SHIFT
int "Maximum NUMA Nodes (as a power of 2)"
default "1" if !DISCONTIGMEM
default "2" if DISCONTIGMEM
depends on NEED_MULTIPLE_NODES
---help---
Accessing memory beyond 1GB (with or w/o PAE) requires 2 memory
zones.
if ISA_ARCOMPACT
config ARC_COMPACT_IRQ_LEVELS
@ -455,6 +467,7 @@ config LINUX_LINK_BASE
config HIGHMEM
bool "High Memory Support"
select DISCONTIGMEM
help
With ARC 2G:2G address split, only upper 2G is directly addressable by
kernel. Enable this to potentially allow access to rest of 2G and PAE

43
arch/arc/include/asm/mmzone.h Normal file
View File

@ -0,0 +1,43 @@
/*
* Copyright (C) 2016 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef _ASM_ARC_MMZONE_H
#define _ASM_ARC_MMZONE_H
#ifdef CONFIG_DISCONTIGMEM
extern struct pglist_data node_data[];
#define NODE_DATA(nid) (&node_data[nid])
static inline int pfn_to_nid(unsigned long pfn)
{
int is_end_low = 1;
if (IS_ENABLED(CONFIG_ARC_HAS_PAE40))
is_end_low = pfn <= virt_to_pfn(0xFFFFFFFFUL);
/*
* node 0: lowmem: 0x8000_0000 to 0xFFFF_FFFF
* node 1: HIGHMEM w/o PAE40: 0x0 to 0x7FFF_FFFF
* HIGHMEM with PAE40: 0x1_0000_0000 to ...
*/
if (pfn >= ARCH_PFN_OFFSET && is_end_low)
return 0;
return 1;
}
static inline int pfn_valid(unsigned long pfn)
{
int nid = pfn_to_nid(pfn);
return (pfn <= node_end_pfn(nid));
}
#endif /* CONFIG_DISCONTIGMEM */
#endif

6
arch/arc/include/asm/page.h
View File

@ -83,7 +83,9 @@ typedef pte_t * pgtable_t;
#define ARCH_PFN_OFFSET virt_to_pfn(CONFIG_LINUX_LINK_BASE)
#ifdef CONFIG_FLATMEM
#define pfn_valid(pfn) (((pfn) - ARCH_PFN_OFFSET) < max_mapnr)
#endif
/*
* __pa, __va, virt_to_page (ALERT: deprecated, don't use them)
@ -95,9 +97,7 @@ typedef pte_t * pgtable_t;
#define __pa(vaddr) ((unsigned long)(vaddr))
#define __va(paddr) ((void *)((unsigned long)(paddr)))
#define virt_to_page(kaddr) \
(mem_map + virt_to_pfn((kaddr) - CONFIG_LINUX_LINK_BASE))
#define virt_to_page(kaddr) pfn_to_page(virt_to_pfn(kaddr))
#define virt_addr_valid(kaddr) pfn_valid(virt_to_pfn(kaddr))
/* Default Permissions for stack/heaps pages (Non Executable) */

54
arch/arc/mm/init.c
View File

@ -30,11 +30,16 @@ static const unsigned long low_mem_start = CONFIG_LINUX_LINK_BASE;
static unsigned long low_mem_sz;
#ifdef CONFIG_HIGHMEM
static unsigned long min_high_pfn;
static unsigned long min_high_pfn, max_high_pfn;
static u64 high_mem_start;
static u64 high_mem_sz;
#endif
#ifdef CONFIG_DISCONTIGMEM
struct pglist_data node_data[MAX_NUMNODES] __read_mostly;
EXPORT_SYMBOL(node_data);
#endif
/* User can over-ride above with "mem=nnn[KkMm]" in cmdline */
static int __init setup_mem_sz(char *str)
{
@ -109,13 +114,11 @@ void __init setup_arch_memory(void)
/* Last usable page of low mem */
max_low_pfn = max_pfn = PFN_DOWN(low_mem_start + low_mem_sz);
#ifdef CONFIG_HIGHMEM
min_high_pfn = PFN_DOWN(high_mem_start);
max_pfn = PFN_DOWN(high_mem_start + high_mem_sz);
#ifdef CONFIG_FLATMEM
/* pfn_valid() uses this */
max_mapnr = max_low_pfn - min_low_pfn;
#endif
max_mapnr = max_pfn - min_low_pfn;
/*------------- bootmem allocator setup -----------------------*/
/*
@ -129,7 +132,7 @@ void __init setup_arch_memory(void)
* the crash
*/
memblock_add(low_mem_start, low_mem_sz);
memblock_add_node(low_mem_start, low_mem_sz, 0);
memblock_reserve(low_mem_start, __pa(_end) - low_mem_start);
#ifdef CONFIG_BLK_DEV_INITRD
@ -149,13 +152,6 @@ void __init setup_arch_memory(void)
zones_size[ZONE_NORMAL] = max_low_pfn - min_low_pfn;
zones_holes[ZONE_NORMAL] = 0;
#ifdef CONFIG_HIGHMEM
zones_size[ZONE_HIGHMEM] = max_pfn - max_low_pfn;
/* This handles the peripheral address space hole */
zones_holes[ZONE_HIGHMEM] = min_high_pfn - max_low_pfn;
#endif
/*
* We can't use the helper free_area_init(zones[]) because it uses
* PAGE_OFFSET to compute the @min_low_pfn which would be wrong
@ -168,6 +164,34 @@ void __init setup_arch_memory(void)
zones_holes); /* holes */
#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).
* 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
*/
node_set_online(1);
min_high_pfn = PFN_DOWN(high_mem_start);
max_high_pfn = PFN_DOWN(high_mem_start + high_mem_sz);
zones_size[ZONE_NORMAL] = 0;
zones_holes[ZONE_NORMAL] = 0;
zones_size[ZONE_HIGHMEM] = max_high_pfn - min_high_pfn;
zones_holes[ZONE_HIGHMEM] = 0;
free_area_init_node(1, /* node-id */
zones_size, /* num pages per zone */
min_high_pfn, /* first pfn of node */
zones_holes); /* holes */
high_memory = (void *)(min_high_pfn << PAGE_SHIFT);
kmap_init();
#endif
@ -185,7 +209,7 @@ void __init mem_init(void)
unsigned long tmp;
reset_all_zones_managed_pages();
for (tmp = min_high_pfn; tmp < max_pfn; tmp++)
for (tmp = min_high_pfn; tmp < max_high_pfn; tmp++)
free_highmem_page(pfn_to_page(tmp));
#endif