diff options
| author | Paul Burton <paul.burton@mips.com> | 2018-07-27 18:23:20 -0700 |
|---|---|---|
| committer | Paul Burton <paul.burton@mips.com> | 2018-07-30 10:27:32 -0700 |
| commit | 6c359eb1dcdb721908f4336171ed8eb6d78190c5 (patch) | |
| tree | 31dc276ff48f12fa8dd187dffa1a829ca3bfdbdc /arch/mips/include/asm/mach-generic | |
| parent | 0494d7ffdcebc6935410ea0719b24ab626675351 (diff) | |
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/include/asm/mach-generic')
| -rw-r--r-- | arch/mips/include/asm/mach-generic/spaces.h | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/arch/mips/include/asm/mach-generic/spaces.h b/arch/mips/include/asm/mach-generic/spaces.h index 952b0fdfda0e..ee5ebe98f6cf 100644 --- a/arch/mips/include/asm/mach-generic/spaces.h +++ b/arch/mips/include/asm/mach-generic/spaces.h @@ -17,9 +17,13 @@ /* * This gives the physical RAM offset. */ -#ifndef PHYS_OFFSET -#define PHYS_OFFSET _AC(0, UL) -#endif +#ifndef __ASSEMBLY__ +# if defined(CONFIG_MIPS_AUTO_PFN_OFFSET) +# define PHYS_OFFSET ((unsigned long)PFN_PHYS(ARCH_PFN_OFFSET)) +# elif !defined(PHYS_OFFSET) +# define PHYS_OFFSET _AC(0, UL) +# endif +#endif /* __ASSEMBLY__ */ #ifdef CONFIG_32BIT #ifdef CONFIG_KVM_GUEST |