linux-kernel - [PATCH v2 cmpxchg 11/13] csky: Emulate one-byte cmpxchg

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Message-Id: <20240501230130.1111603-11-paulmck@kernel.org>
Date: Wed,  1 May 2024 16:01:28 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: elver@...gle.com,
	akpm@...ux-foundation.org,
	tglx@...utronix.de,
	peterz@...radead.org,
	dianders@...omium.org,
	pmladek@...e.com,
	arnd@...db.de,
	torvalds@...ux-foundation.org,
	kernel-team@...a.com,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Yujie Liu <yujie.liu@...el.com>,
	Guo Ren <guoren@...nel.org>,
	linux-csky@...r.kernel.org
Subject: [PATCH v2 cmpxchg 11/13] csky: Emulate one-byte cmpxchg

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

[ paulmck: Apply kernel test robot feedback. ]
[ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]

Co-developed-by: Yujie Liu <yujie.liu@...el.com>
Signed-off-by: Yujie Liu <yujie.liu@...el.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Tested-by: Yujie Liu <yujie.liu@...el.com>
Cc: Guo Ren <guoren@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: <linux-csky@...r.kernel.org>
---
 arch/csky/Kconfig               |  1 +
 arch/csky/include/asm/cmpxchg.h | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index d3ac36751ad1f..5479707eb5d10 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_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..db6dda47184e4 100644
--- a/arch/csky/include/asm/cmpxchg.h
+++ b/arch/csky/include/asm/cmpxchg.h
@@ -6,6 +6,7 @@
 #ifdef CONFIG_SMP
 #include <linux/bug.h>
 #include <asm/barrier.h>
+#include <linux/cmpxchg-emu.h>
 
 #define __xchg_relaxed(new, ptr, size)				\
 ({								\
@@ -61,6 +62,9 @@
 	__typeof__(old) __old = (old);				\
 	__typeof__(*(ptr)) __ret;				\
 	switch (size) {						\
+	case 1:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -91,6 +95,9 @@
 	__typeof__(old) __old = (old);				\
 	__typeof__(*(ptr)) __ret;				\
 	switch (size) {						\
+	case 1:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -122,6 +129,9 @@
 	__typeof__(old) __old = (old);				\
 	__typeof__(*(ptr)) __ret;				\
 	switch (size) {						\
+	case 1:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		RELEASE_FENCE					\
-- 
2.40.1