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openrisc: add 1 and 2 byte cmpxchg support

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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 <peterz@infradead.org>
Signed-off-by: Stafford Horne <shorne@gmail.com>
This commit is contained in:
Stafford Horne 2017-03-23 23:27:12 +09:00
parent 91993c8c2e
commit 489e0f802d
1 changed files with 119 additions and 36 deletions
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155
arch/openrisc/include/asm/cmpxchg.h
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@ -1,32 +1,29 @@
/*
* 1,2 and 4 byte cmpxchg and xchg implementations for OpenRISC.
*
* Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
* Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
*
* 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 <linux/types.h>
/*
* 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 <linux/bitops.h>
#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"
@ -43,28 +40,9 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
return old;
}
#define cmpxchg(ptr, o, n) \
({ \
(__typeof__(*(ptr))) __cmpxchg((ptr), \
(unsigned long)(o), \
(unsigned long)(n), \
sizeof(*(ptr))); \
})
/*
* 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);
static inline unsigned long __xchg(unsigned long val, volatile void *ptr,
int size)
static inline unsigned long xchg_u32(volatile void *ptr,
unsigned long val)
{
if (size != 4) {
__xchg_called_with_bad_pointer();
return val;
}
__asm__ __volatile__(
"1: l.lwa %0, 0(%1) \n"
" l.swa 0(%1), %2 \n"
@ -77,10 +55,115 @@ static inline unsigned long __xchg(unsigned long val, volatile void *ptr,
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), \
(unsigned long)(o), \
(unsigned long)(n), \
sizeof(*(ptr))); \
})
/*
* This function doesn't exist, so you'll get a linker error if
* something tries to do an invalidly-sized xchg().
*/
extern unsigned long __xchg_called_with_bad_pointer(void)
__compiletime_error("Bad argument size for xchg");
static inline unsigned long __xchg(volatile void *ptr, unsigned long with,
int size)
{
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();
}
}
#define xchg(ptr, with) \
({ \
(__typeof__(*(ptr))) __xchg((unsigned long)(with), \
(ptr), \
(__typeof__(*(ptr))) __xchg((ptr), \
(unsigned long)(with), \
sizeof(*(ptr))); \
})