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| 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/kernel | |
| parent | 0494d7ffdcebc6935410ea0719b24ab626675351 (diff) | |
| download | op-kernel-dev-6c359eb1dcdb721908f4336171ed8eb6d78190c5.zip op-kernel-dev-6c359eb1dcdb721908f4336171ed8eb6d78190c5.tar.gz | |
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/kernel')
| -rw-r--r-- | arch/mips/kernel/setup.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c index 3d45243..c71d1eb 100644 --- a/arch/mips/kernel/setup.c +++ b/arch/mips/kernel/setup.c @@ -85,6 +85,11 @@ static struct resource bss_resource = { .name = "Kernel bss", }; static void *detect_magic __initdata = detect_memory_region; +#ifdef CONFIG_MIPS_AUTO_PFN_OFFSET +unsigned long ARCH_PFN_OFFSET; +EXPORT_SYMBOL(ARCH_PFN_OFFSET); +#endif + void __init add_memory_region(phys_addr_t start, phys_addr_t size, long type) { int x = boot_mem_map.nr_map; @@ -442,6 +447,12 @@ static void __init bootmem_init(void) mapstart = max(reserved_end, start); } + if (min_low_pfn >= max_low_pfn) + panic("Incorrect memory mapping !!!"); + +#ifdef CONFIG_MIPS_AUTO_PFN_OFFSET + ARCH_PFN_OFFSET = PFN_UP(ramstart); +#else /* * Reserve any memory between the start of RAM and PHYS_OFFSET */ @@ -449,8 +460,6 @@ static void __init bootmem_init(void) add_memory_region(PHYS_OFFSET, ramstart - PHYS_OFFSET, BOOT_MEM_RESERVED); - if (min_low_pfn >= max_low_pfn) - panic("Incorrect memory mapping !!!"); if (min_low_pfn > ARCH_PFN_OFFSET) { pr_info("Wasting %lu bytes for tracking %lu unused pages\n", (min_low_pfn - ARCH_PFN_OFFSET) * sizeof(struct page), @@ -460,6 +469,7 @@ static void __init bootmem_init(void) ARCH_PFN_OFFSET - min_low_pfn); } min_low_pfn = ARCH_PFN_OFFSET; +#endif /* * Determine low and high memory ranges |
