linux-kernel - [PATCH RFC cmpxchg 4/8] csky: Emulate one-byte and two-byte cmpxchg

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Date: Mon,  1 Apr 2024 14:39:46 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: kernel-team@...a.com,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Guo Ren <guoren@...nel.org>,
	linux-csky@...r.kernel.org
Subject: [PATCH RFC cmpxchg 4/8] csky: Emulate one-byte and two-byte cmpxchg

Use the new cmpxchg_emu_u8() and cmpxchg_emu_u16() to emulate one-byte
and two-byte cmpxchg() on csky.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Guo Ren <guoren@...nel.org>
Cc: <linux-csky@...r.kernel.org>
---
 arch/csky/Kconfig               |  1 +
 arch/csky/include/asm/cmpxchg.h | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index d3ac36751ad1f..860d4e02d6295 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -37,6 +37,7 @@ config CSKY
 	select ARCH_INLINE_SPIN_UNLOCK_BH if !PREEMPTION
 	select ARCH_INLINE_SPIN_UNLOCK_IRQ if !PREEMPTION
 	select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION
+	select ARCH_NEED_CMPXCHG_1_2_EMU
 	select ARCH_WANT_FRAME_POINTERS if !CPU_CK610 && $(cc-option,-mbacktrace)
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 	select COMMON_CLK
diff --git a/arch/csky/include/asm/cmpxchg.h b/arch/csky/include/asm/cmpxchg.h
index 916043b845f14..848a8691c5a2a 100644
--- a/arch/csky/include/asm/cmpxchg.h
+++ b/arch/csky/include/asm/cmpxchg.h
@@ -61,6 +61,12 @@
 	__typeof__(old) __old = (old);				\
 	__typeof__(*(ptr)) __ret;				\
 	switch (size) {						\
+	case 1:							\
+		__ret = cmpxchg_emu_u8((volatile u8 *)__ptr, __old, __new); \
+		break;						\
+	case 2:							\
+		__ret = cmpxchg_emu_u16((volatile u16 *)__ptr, __old, __new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -91,6 +97,12 @@
 	__typeof__(old) __old = (old);				\
 	__typeof__(*(ptr)) __ret;				\
 	switch (size) {						\
+	case 1:							\
+		__ret = cmpxchg_emu_u8((volatile u8 *)__ptr, __old, __new); \
+		break;						\
+	case 2:							\
+		__ret = cmpxchg_emu_u16((volatile u16 *)__ptr, __old, __new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -122,6 +134,12 @@
 	__typeof__(old) __old = (old);				\
 	__typeof__(*(ptr)) __ret;				\
 	switch (size) {						\
+	case 1:							\
+		__ret = cmpxchg_emu_u8((volatile u8 *)__ptr, __old, __new); \
+		break;						\
+	case 2:							\
+		__ret = cmpxchg_emu_u16((volatile u16 *)__ptr, __old, __new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		RELEASE_FENCE					\
-- 
2.40.1