linux-kernel - [PATCH RFC cmpxchg 2/8] sparc: Emulate one-byte and two-byte cmpxchg

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Date: Mon,  1 Apr 2024 14:39:44 -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>,
	"David S. Miller" <davem@...emloft.net>,
	Andreas Larsson <andreas@...sler.com>,
	Palmer Dabbelt <palmer@...osinc.com>,
	Arnd Bergmann <arnd@...db.de>,
	Marco Elver <elver@...gle.com>
Subject: [PATCH RFC cmpxchg 2/8] sparc: 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 32-bit sparc.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Andreas Larsson <andreas@...sler.com>
Cc: Palmer Dabbelt <palmer@...osinc.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Marco Elver <elver@...gle.com>
---
 arch/sparc/Kconfig                  | 1 +
 arch/sparc/include/asm/cmpxchg_32.h | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 11bf9d312318c..e6d1bbc4fedd0 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -55,6 +55,7 @@ config SPARC32
 	select ARCH_32BIT_OFF_T
 	select ARCH_HAS_CPU_FINALIZE_INIT if !SMP
 	select ARCH_HAS_SYNC_DMA_FOR_CPU
+	select ARCH_NEED_CMPXCHG_1_2_EMU
 	select CLZ_TAB
 	select DMA_DIRECT_REMAP
 	select GENERIC_ATOMIC64
diff --git a/arch/sparc/include/asm/cmpxchg_32.h b/arch/sparc/include/asm/cmpxchg_32.h
index d0af82c240b73..8eb483b5887a1 100644
--- a/arch/sparc/include/asm/cmpxchg_32.h
+++ b/arch/sparc/include/asm/cmpxchg_32.h
@@ -41,11 +41,17 @@ void __cmpxchg_called_with_bad_pointer(void);
 /* we only need to support cmpxchg of a u32 on sparc */
 unsigned long __cmpxchg_u32(volatile u32 *m, u32 old, u32 new_);
 
+#include <linux/cmpxchg-emu.h>
+
 /* don't worry...optimizer will get rid of most of this */
 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((u32 *)ptr, (u32)old, (u32)new_);
 	default:
-- 
2.40.1