diff options
Diffstat (limited to 'arch/riscv/include/asm/cmpxchg.h')
| -rw-r--r-- | arch/riscv/include/asm/cmpxchg.h | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h index 808b4c78462e..ebbce134917c 100644 --- a/arch/riscv/include/asm/cmpxchg.h +++ b/arch/riscv/include/asm/cmpxchg.h @@ -8,7 +8,10 @@ #include <linux/bug.h> +#include <asm/alternative-macros.h> #include <asm/fence.h> +#include <asm/hwcap.h> +#include <asm/insn-def.h> #define __arch_xchg_masked(sc_sfx, prepend, append, r, p, n) \ ({ \ @@ -223,4 +226,59 @@ arch_cmpxchg_release((ptr), (o), (n)); \ }) +#ifdef CONFIG_RISCV_ISA_ZAWRS +/* + * Despite wrs.nto being "WRS-with-no-timeout", in the absence of changes to + * @val we expect it to still terminate within a "reasonable" amount of time + * for an implementation-specific other reason, a pending, locally-enabled + * interrupt, or because it has been configured to raise an illegal + * instruction exception. + */ +static __always_inline void __cmpwait(volatile void *ptr, + unsigned long val, + int size) +{ + unsigned long tmp; + + asm goto(ALTERNATIVE("j %l[no_zawrs]", "nop", + 0, RISCV_ISA_EXT_ZAWRS, 1) + : : : : no_zawrs); + + switch (size) { + case 4: + asm volatile( + " lr.w %0, %1\n" + " xor %0, %0, %2\n" + " bnez %0, 1f\n" + ZAWRS_WRS_NTO "\n" + "1:" + : "=&r" (tmp), "+A" (*(u32 *)ptr) + : "r" (val)); + break; +#if __riscv_xlen == 64 + case 8: + asm volatile( + " lr.d %0, %1\n" + " xor %0, %0, %2\n" + " bnez %0, 1f\n" + ZAWRS_WRS_NTO "\n" + "1:" + : "=&r" (tmp), "+A" (*(u64 *)ptr) + : "r" (val)); + break; +#endif + default: + BUILD_BUG(); + } + + return; + +no_zawrs: + asm volatile(RISCV_PAUSE : : : "memory"); +} + +#define __cmpwait_relaxed(ptr, val) \ + __cmpwait((ptr), (unsigned long)(val), sizeof(*(ptr))) +#endif + #endif /* _ASM_RISCV_CMPXCHG_H */ |