linux-kernel - [PATCH v3 cmpxchg 2/4] sh: Emulate one-byte cmpxchg

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Message-Id: <20240604170437.2362545-2-paulmck@kernel.org>
Date: Tue,  4 Jun 2024 10:04:35 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: linux-arch@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	kernel-team@...a.com,
	elver@...gle.com,
	akpm@...ux-foundation.org,
	tglx@...utronix.de,
	peterz@...radead.org,
	dianders@...omium.org,
	pmladek@...e.com,
	torvalds@...ux-foundation.org,
	arnd@...db.de,
	"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 v3 cmpxchg 2/4] sh: Emulate one-byte cmpxchg

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

[ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]
[ paulmck: Apply feedback from Naresh Kamboju. ]
[ Apply Geert Uytterhoeven feedback. ]

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: Arnd Bergmann <arnd@...db.de>
Cc: <linux-sh@...r.kernel.org>
---
 arch/sh/Kconfig               | 1 +
 arch/sh/include/asm/cmpxchg.h | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 5e6a3ead51fb1..f723e2256c9c1 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_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..1e5dc5ccf7bf5 100644
--- a/arch/sh/include/asm/cmpxchg.h
+++ b/arch/sh/include/asm/cmpxchg.h
@@ -9,6 +9,7 @@
 
 #include <linux/compiler.h>
 #include <linux/types.h>
+#include <linux/cmpxchg-emu.h>
 
 #if defined(CONFIG_GUSA_RB)
 #include <asm/cmpxchg-grb.h>
@@ -56,6 +57,8 @@ static inline unsigned long __cmpxchg(volatile void * ptr, unsigned long old,
 		unsigned long new, int size)
 {
 	switch (size) {
+	case 1:
+		return cmpxchg_emu_u8(ptr, old, new);
 	case 4:
 		return __cmpxchg_u32(ptr, old, new);
 	}
-- 
2.40.1