diff options
| author | Vineet Gupta <vgupta@synopsys.com> | 2016-04-18 10:49:56 +0530 |
|---|---|---|
| committer | Vineet Gupta <vgupta@synopsys.com> | 2016-05-05 16:35:46 +0530 |
| commit | 26f9d5fd82ca20fe536cb493ec7cf5628f8997e5 (patch) | |
| tree | c41863d4e667587efb23cf46e04d013e4ac2ea33 /arch/arc/Kconfig | |
| parent | 2519d753676bdf2460fbbcde276d5b6ba8d6b695 (diff) | |
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>
Diffstat (limited to 'arch/arc/Kconfig')
| -rw-r--r-- | arch/arc/Kconfig | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index ec4791ea6911..a8767430df7d 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -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 |