linux-kernel - [PATCH RFC cmpxchg 5/8] sh: Emulate one-byte and two-byte cmpxchg

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Date: Mon,  1 Apr 2024 14:39:47 -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>,
	Andi Shyti <andi.shyti@...ux.intel.com>,
	Palmer Dabbelt <palmer@...osinc.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	linux-sh@...r.kernel.org
Subject: [PATCH RFC cmpxchg 5/8] sh: 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 sh.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Andi Shyti <andi.shyti@...ux.intel.com>
Cc: Palmer Dabbelt <palmer@...osinc.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: <linux-sh@...r.kernel.org>
---
 arch/sh/Kconfig               | 1 +
 arch/sh/include/asm/cmpxchg.h | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 2ad3e29f0ebec..43a121c6ca0f3 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -16,6 +16,7 @@ config SUPERH
 	select ARCH_HIBERNATION_POSSIBLE if MMU
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_WANT_IPC_PARSE_VERSION
+	select ARCH_NEED_CMPXCHG_1_2_EMU
 	select CPU_NO_EFFICIENT_FFS
 	select DMA_DECLARE_COHERENT
 	select GENERIC_ATOMIC64
diff --git a/arch/sh/include/asm/cmpxchg.h b/arch/sh/include/asm/cmpxchg.h
index 5d617b3ef78f7..18233cc14419e 100644
--- a/arch/sh/include/asm/cmpxchg.h
+++ b/arch/sh/include/asm/cmpxchg.h
@@ -56,6 +56,10 @@ static inline unsigned long __cmpxchg(volatile void * ptr, unsigned long old,
 		unsigned long new, int size)
 {
 	switch (size) {
+	case 1:
+		return cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
+	case 2:
+		return cmpxchg_emu_u16((volatile u16 *)ptr, old, new);
 	case 4:
 		return __cmpxchg_u32(ptr, old, new);
 	}
-- 
2.40.1