From 489e0f802db708c69004f64d92a3e1b70731614a Mon Sep 17 00:00:00 2001 From: Stafford Horne Date: Thu, 23 Mar 2017 23:27:12 +0900 Subject: openrisc: add 1 and 2 byte cmpxchg support OpenRISC only supports hardware instructions that perform 4 byte atomic operations. For enabling qrwlocks for upcoming SMP support 1 and 2 byte implementations are needed. To do this we leverage the 4 byte atomic operations and shift/mask the 1 and 2 byte areas as needed. This heavily borrows ideas and routines from sh and mips, which do something similar. Cc: Peter Zijlstra Signed-off-by: Stafford Horne --- arch/openrisc/include/asm/cmpxchg.h | 147 ++++++++++++++++++++++++++++-------- 1 file changed, 115 insertions(+), 32 deletions(-) (limited to 'arch/openrisc') diff --git a/arch/openrisc/include/asm/cmpxchg.h b/arch/openrisc/include/asm/cmpxchg.h index f0a5d8b844d6..d29f7db53906 100644 --- a/arch/openrisc/include/asm/cmpxchg.h +++ b/arch/openrisc/include/asm/cmpxchg.h @@ -1,32 +1,29 @@ /* + * 1,2 and 4 byte cmpxchg and xchg implementations for OpenRISC. + * * Copyright (C) 2014 Stefan Kristiansson + * Copyright (C) 2017 Stafford Horne * * This file is licensed under the terms of the GNU General Public License * version 2. This program is licensed "as is" without any warranty of any * kind, whether express or implied. + * + * Note: + * The portable implementations of 1 and 2 byte xchg and cmpxchg using a 4 + * byte cmpxchg is sourced heavily from the sh and mips implementations. */ #ifndef __ASM_OPENRISC_CMPXCHG_H #define __ASM_OPENRISC_CMPXCHG_H #include - -/* - * This function doesn't exist, so you'll get a linker error - * if something tries to do an invalid cmpxchg(). - */ -extern void __cmpxchg_called_with_bad_pointer(void); +#include #define __HAVE_ARCH_CMPXCHG 1 -static inline unsigned long -__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size) +static inline unsigned long cmpxchg_u32(volatile void *ptr, + unsigned long old, unsigned long new) { - if (size != 4) { - __cmpxchg_called_with_bad_pointer(); - return old; - } - __asm__ __volatile__( "1: l.lwa %0, 0(%1) \n" " l.sfeq %0, %2 \n" @@ -43,6 +40,97 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size) return old; } +static inline unsigned long xchg_u32(volatile void *ptr, + unsigned long val) +{ + __asm__ __volatile__( + "1: l.lwa %0, 0(%1) \n" + " l.swa 0(%1), %2 \n" + " l.bnf 1b \n" + " l.nop \n" + : "=&r"(val) + : "r"(ptr), "r"(val) + : "cc", "memory"); + + return val; +} + +static inline u32 cmpxchg_small(volatile void *ptr, u32 old, u32 new, + int size) +{ + int off = (unsigned long)ptr % sizeof(u32); + volatile u32 *p = ptr - off; +#ifdef __BIG_ENDIAN + int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE; +#else + int bitoff = off * BITS_PER_BYTE; +#endif + u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff; + u32 load32, old32, new32; + u32 ret; + + load32 = READ_ONCE(*p); + + while (true) { + ret = (load32 & bitmask) >> bitoff; + if (old != ret) + return ret; + + old32 = (load32 & ~bitmask) | (old << bitoff); + new32 = (load32 & ~bitmask) | (new << bitoff); + + /* Do 32 bit cmpxchg */ + load32 = cmpxchg_u32(p, old32, new32); + if (load32 == old32) + return old; + } +} + +/* xchg */ + +static inline u32 xchg_small(volatile void *ptr, u32 x, int size) +{ + int off = (unsigned long)ptr % sizeof(u32); + volatile u32 *p = ptr - off; +#ifdef __BIG_ENDIAN + int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE; +#else + int bitoff = off * BITS_PER_BYTE; +#endif + u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff; + u32 oldv, newv; + u32 ret; + + do { + oldv = READ_ONCE(*p); + ret = (oldv & bitmask) >> bitoff; + newv = (oldv & ~bitmask) | (x << bitoff); + } while (cmpxchg_u32(p, oldv, newv) != oldv); + + return ret; +} + +/* + * This function doesn't exist, so you'll get a linker error + * if something tries to do an invalid cmpxchg(). + */ +extern unsigned long __cmpxchg_called_with_bad_pointer(void) + __compiletime_error("Bad argument size for cmpxchg"); + +static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, + unsigned long new, int size) +{ + switch (size) { + case 1: + case 2: + return cmpxchg_small(ptr, old, new, size); + case 4: + return cmpxchg_u32(ptr, old, new); + default: + return __cmpxchg_called_with_bad_pointer(); + } +} + #define cmpxchg(ptr, o, n) \ ({ \ (__typeof__(*(ptr))) __cmpxchg((ptr), \ @@ -55,32 +143,27 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size) * This function doesn't exist, so you'll get a linker error if * something tries to do an invalidly-sized xchg(). */ -extern void __xchg_called_with_bad_pointer(void); +extern unsigned long __xchg_called_with_bad_pointer(void) + __compiletime_error("Bad argument size for xchg"); -static inline unsigned long __xchg(unsigned long val, volatile void *ptr, - int size) +static inline unsigned long __xchg(volatile void *ptr, unsigned long with, + int size) { - if (size != 4) { - __xchg_called_with_bad_pointer(); - return val; + switch (size) { + case 1: + case 2: + return xchg_small(ptr, with, size); + case 4: + return xchg_u32(ptr, with); + default: + return __xchg_called_with_bad_pointer(); } - - __asm__ __volatile__( - "1: l.lwa %0, 0(%1) \n" - " l.swa 0(%1), %2 \n" - " l.bnf 1b \n" - " l.nop \n" - : "=&r"(val) - : "r"(ptr), "r"(val) - : "cc", "memory"); - - return val; } #define xchg(ptr, with) \ ({ \ - (__typeof__(*(ptr))) __xchg((unsigned long)(with), \ - (ptr), \ + (__typeof__(*(ptr))) __xchg((ptr), \ + (unsigned long)(with), \ sizeof(*(ptr))); \ }) -- cgit v1.2.1