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arch/sparc: Introduce xchg16 for SPARC

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SPARC supports 32 bit and 64 bit xchg right now. Add the support
for 16 bit (2 byte) xchg. This is required to support queued spinlock
feature which uses 2 byte xchg. This is achieved using 4 byte cas
instructions with byte manipulations.

Also re-arranged the code to call __cmpxchg_u32 inside xchg16.

Signed-off-by: Babu Moger <babu.moger@oracle.com>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Vijay Kumar <vijay.ac.kumar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Babu Moger 2017-05-24 17:55:14 -06:00 committed by David S. Miller
parent a37594f198
commit 79d39e2bab
1 changed files with 39 additions and 10 deletions
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49
arch/sparc/include/asm/cmpxchg_64.h
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@ -6,6 +6,17 @@
#ifndef __ARCH_SPARC64_CMPXCHG__
#define __ARCH_SPARC64_CMPXCHG__
static inline unsigned long
__cmpxchg_u32(volatile int *m, int old, int new)
{
__asm__ __volatile__("cas [%2], %3, %0"
: "=&r" (new)
: "0" (new), "r" (m), "r" (old)
: "memory");
return new;
}
static inline unsigned long xchg32(__volatile__ unsigned int *m, unsigned int val)
{
unsigned long tmp1, tmp2;
@ -44,10 +55,38 @@ static inline unsigned long xchg64(__volatile__ unsigned long *m, unsigned long
void __xchg_called_with_bad_pointer(void);
/*
* Use 4 byte cas instruction to achieve 2 byte xchg. Main logic
* here is to get the bit shift of the byte we are interested in.
* The XOR is handy for reversing the bits for big-endian byte order.
*/
static inline unsigned long
xchg16(__volatile__ unsigned short *m, unsigned short val)
{
unsigned long maddr = (unsigned long)m;
int bit_shift = (((unsigned long)m & 2) ^ 2) << 3;
unsigned int mask = 0xffff << bit_shift;
unsigned int *ptr = (unsigned int *) (maddr & ~2);
unsigned int old32, new32, load32;
/* Read the old value */
load32 = *ptr;
do {
old32 = load32;
new32 = (load32 & (~mask)) | val << bit_shift;
load32 = __cmpxchg_u32(ptr, old32, new32);
} while (load32 != old32);
return (load32 & mask) >> bit_shift;
}
static inline unsigned long __xchg(unsigned long x, __volatile__ void * ptr,
int size)
{
switch (size) {
case 2:
return xchg16(ptr, x);
case 4:
return xchg32(ptr, x);
case 8:
@ -65,16 +104,6 @@ static inline unsigned long __xchg(unsigned long x, __volatile__ void * ptr,
#include <asm-generic/cmpxchg-local.h>
static inline unsigned long
__cmpxchg_u32(volatile int *m, int old, int new)
{
__asm__ __volatile__("cas [%2], %3, %0"
: "=&r" (new)
: "0" (new), "r" (m), "r" (old)
: "memory");
return new;
}
static inline unsigned long
__cmpxchg_u64(volatile long *m, unsigned long old, unsigned long new)