[PATCH 4/6] csky: Emulate two-byte cmpxchg

[Bradley Morgan <brads@mainlining.org>]

csky has no byte or halfword atomic memory operations, so the
__cmpxchg_relaxed(), __cmpxchg_acquire() and __cmpxchg() switches
each route case 1 through cmpxchg_emu_u8() and leave case 2 to
fall into the BUILD_BUG() default. Route case 2 in all three
through the new cmpxchg_emu_u16().

arch_cmpxchg_local() maps to __cmpxchg_relaxed() and so picks up
case 2 automatically.

Signed-off-by: Bradley Morgan <brads@mainlining.org>
---
 arch/csky/include/asm/cmpxchg.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/csky/include/asm/cmpxchg.h b/arch/csky/include/asm/cmpxchg.h
index db6dda47184e..a6a4805064a4 100644
--- a/arch/csky/include/asm/cmpxchg.h
+++ b/arch/csky/include/asm/cmpxchg.h
@@ -65,6 +65,9 @@
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
 		break;						\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -98,6 +101,9 @@
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
 		break;						\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -132,6 +138,9 @@
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
 		break;						\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		RELEASE_FENCE					\
-- 
2.47.3