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| author | Paul Burton <paul.burton@mips.com> | 2018-07-28 04:23:20 +0300 |
|---|---|---|
| committer | Paul Burton <paul.burton@mips.com> | 2018-07-30 20:27:32 +0300 |
| commit | 6c359eb1dcdb721908f4336171ed8eb6d78190c5 (patch) | |
| tree | 31dc276ff48f12fa8dd187dffa1a829ca3bfdbdc /arch/mips/Kconfig | |
| parent | 0494d7ffdcebc6935410ea0719b24ab626675351 (diff) | |
| download | linux-6c359eb1dcdb721908f4336171ed8eb6d78190c5.tar.xz | |
MIPS: Allow auto-dection of ARCH_PFN_OFFSET & PHYS_OFFSET
On systems where physical memory begins at a non-zero address, defining
PHYS_OFFSET (which influences ARCH_PFN_OFFSET) can save us time & memory
by avoiding book-keeping for pages from address zero to the start of
memory.
Some MIPS platforms already make use of this, but with the definition of
PHYS_OFFSET being compile-time constant it hasn't been possible to
enable this optimization for a kernel which may run on systems with
varying physical memory base addresses.
Introduce a new Kconfig option CONFIG_MIPS_AUTO_PFN_OFFSET which, when
enabled, makes ARCH_PFN_OFFSET a variable & detects it from the boot
memory map (which for example may have been populated from DT). The
relationship with PHYS_OFFSET is reversed, with PHYS_OFFSET now being
based on ARCH_PFN_OFFSET. This is because ARCH_PFN_OFFSET is used far
more often, so avoiding the need for runtime calculation gives us a
smaller impact on kernel text size (0.1% rather than 0.15% for
64r6el_defconfig).
Signed-off-by: Paul Burton <paul.burton@mips.com>
Suggested-by: Vladimir Kondratiev <vladimir.kondratiev@intel.com>
Patchwork: https://patchwork.linux-mips.org/patch/20048/
Cc: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Diffstat (limited to 'arch/mips/Kconfig')
| -rw-r--r-- | arch/mips/Kconfig | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 10256056647c..fbf7f678e856 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -2985,6 +2985,9 @@ config PGTABLE_LEVELS default 3 if 64BIT && !PAGE_SIZE_64KB default 2 +config MIPS_AUTO_PFN_OFFSET + bool + source "init/Kconfig" source "kernel/Kconfig.freezer" |