[PATCH 4/5] csky: Emulate two-byte cmpxchg

["Paul E. McKenney" <paulmck@kernel.org>]

From: Bradley Morgan <brads@mainlining.org>

C-SKY has no two-byte atomic compare and swap, so the __cmpxchg()
macros let case 2 fall through to BUILD_BUG() via default, and a
two-byte cmpxchg() fails the build.

Route case 2 through the new cmpxchg_emu_u16(), which narrows the
old and new values itself, so all three orderings, relaxed, acquire
and full, keep the (uintptr_t) casts the case 1 path already uses.

Signed-off-by: Bradley Morgan <brads@mainlining.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.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 db6dda47184e4..6f3ca79e54acf 100644
--- a/arch/csky/include/asm/cmpxchg.h
+++ b/arch/csky/include/asm/cmpxchg.h
@@ -64,6 +64,9 @@
 	switch (size) {						\
 	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, (unsigned long)__old, (unsigned long)__new); \
 		break;						\
 	case 4:							\
 		asm volatile (					\
@@ -97,6 +100,9 @@
 	switch (size) {						\
 	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, (unsigned long)__old, (unsigned long)__new); \
 		break;						\
 	case 4:							\
 		asm volatile (					\
@@ -131,6 +137,9 @@
 	switch (size) {						\
 	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, (unsigned long)__old, (unsigned long)__new); \
 		break;						\
 	case 4:							\
 		asm volatile (					\
-- 
2.40.1