diff options
Diffstat (limited to 'arch/mips/kernel')
| -rw-r--r-- | arch/mips/kernel/Makefile | 2 | ||||
| -rw-r--r-- | arch/mips/kernel/cmpxchg.c | 52 |
2 files changed, 53 insertions, 1 deletions
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile index f0edd7e8a0b7..46c0581256f1 100644 --- a/arch/mips/kernel/Makefile +++ b/arch/mips/kernel/Makefile @@ -4,7 +4,7 @@ extra-y := head.o vmlinux.lds -obj-y += cpu-probe.o branch.o elf.o entry.o genex.o idle.o irq.o \ +obj-y += cmpxchg.o cpu-probe.o branch.o elf.o entry.o genex.o idle.o irq.o \ process.o prom.o ptrace.o reset.o setup.o signal.o \ syscall.o time.o topology.o traps.o unaligned.o watch.o \ vdso.o cacheinfo.o diff --git a/arch/mips/kernel/cmpxchg.c b/arch/mips/kernel/cmpxchg.c new file mode 100644 index 000000000000..5acfbf9fb2c5 --- /dev/null +++ b/arch/mips/kernel/cmpxchg.c @@ -0,0 +1,52 @@ +/* + * Copyright (C) 2017 Imagination Technologies + * Author: Paul Burton <paul.burton@imgtec.com> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2 of the License, or (at your + * option) any later version. + */ + +#include <linux/bitops.h> +#include <asm/cmpxchg.h> + +unsigned long __xchg_small(volatile void *ptr, unsigned long val, unsigned int size) +{ + u32 old32, new32, load32, mask; + volatile u32 *ptr32; + unsigned int shift; + + /* Check that ptr is naturally aligned */ + WARN_ON((unsigned long)ptr & (size - 1)); + + /* Mask value to the correct size. */ + mask = GENMASK((size * BITS_PER_BYTE) - 1, 0); + val &= mask; + + /* + * Calculate a shift & mask that correspond to the value we wish to + * exchange within the naturally aligned 4 byte integerthat includes + * it. + */ + shift = (unsigned long)ptr & 0x3; + if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)) + shift ^= sizeof(u32) - size; + shift *= BITS_PER_BYTE; + mask <<= shift; + + /* + * Calculate a pointer to the naturally aligned 4 byte integer that + * includes our byte of interest, and load its value. + */ + ptr32 = (volatile u32 *)((unsigned long)ptr & ~0x3); + load32 = *ptr32; + + do { + old32 = load32; + new32 = (load32 & ~mask) | (val << shift); + load32 = cmpxchg(ptr32, old32, new32); + } while (load32 != old32); + + return (load32 & mask) >> shift; +} |