Initial HIGHMEM support on ARC was introduced for PAE40 where the low
memory (0x8000_ based) and high memory (0x1__) 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_ 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 = <0x8000 0x2 /* 512MB: lowmem */
0x 0x1000>; /* 256MB: highmem */
}
Signed-off-by: Noam Camus
Signed-off-by: Vineet Gupta
---
Aplogies for the extraneous CC. While this is an ARC only patch, having mm
mm glance over it will be much appreicated, to see if this is the right way
to achieve what i needed. FWIW system with this patch boots fine and can
access highmem pages alright.
---
arch/arc/Kconfig | 13 ++
arch/arc/include/asm/mmzone.h | 33 ++
arch/arc/include/asm/page.h| 6 ++---
arch/arc/include/asm/pgtable.h | 4 +---
arch/arc/mm/init.c | 54 ++
5 files changed, 89 insertions(+), 21 deletions(-)
create mode 100644 arch/arc/include/asm/mmzone.h
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 12d0284a46e5..1025da212fbd 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -56,6 +56,9 @@ config GENERIC_CSUM
config RWSEM_GENERIC_SPINLOCK
def_bool y
+config ARCH_DISCONTIGMEM_ENABLE
+ def_bool y
+
config ARCH_FLATMEM_ENABLE
def_bool y
@@ -345,6 +348,15 @@ 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
@@ -453,6 +465,7 @@ 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
diff --git a/arch/arc/include/asm/mmzone.h b/arch/arc/include/asm/mmzone.h
new file mode 100644
index ..a4cc82f723bc
--- /dev/null
+++ b/arch/arc/include/asm/mmzone.h
@@ -0,0 +1,33 @@
+/*
+ * 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)
+{
+ if (pfn >= ARCH_PFN_OFFSET)
+ 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
diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
index 36da89e2c853..3361f5888005 100644
--- a/arch/arc/include/asm/page.h
+++ b/arch/arc/include/asm/page.h
@@ -76,7 +76,9 @@ typedef pte_t * pgtable_t;
#define ARCH_PFN_OFFSETvirt_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)
@@ -88,9 +90,7 @@ 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) */
diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index 7d6c93e63adf..cb756f982b86 100644
--- a/arch/arc/include/asm/pgtable.h
+++ b/arch/arc/include/asm/pgtable.h
@@ -278,11 +278,9 @@ static inline void pmd_set(pmd_t *pmdp,
