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@xxxxxxxxxx>
Reviewed-by: Håkon Bugge <haakon.bugge@xxxxxxxxxx>
Reviewed-by: Steven Sistare <steven.sistare@xxxxxxxxxx>
Reviewed-by: Shannon Nelson <shannon.nelson@xxxxxxxxxx>
Reviewed-by: Jane Chu <jane.chu@xxxxxxxxxx>
Reviewed-by: Vijay Kumar <vijay.ac.kumar@xxxxxxxxxx>
---
arch/sparc/include/asm/cmpxchg_64.h | 49 +++++++++++++++++++++++++++-------
1 files changed, 39 insertions(+), 10 deletions(-)
diff --git a/arch/sparc/include/asm/cmpxchg_64.h b/arch/sparc/include/asm/cmpxchg_64.h
index 65bfae0..a6c9fe3 100644
--- a/arch/sparc/include/asm/cmpxchg_64.h
+++ b/arch/sparc/include/asm/cmpxchg_64.h
@@ -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 int 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)
--
1.7.1
