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From: Bradley Morgan <brads@mainlining.org>
To: akpm@linux-foundation.org, vgupta@kernel.org, guoren@kernel.org,
	chris@zankel.net, jcmvbkbc@gmail.com
Cc: arnd@arndb.de, paulmck@kernel.org, david.laight.linux@gmail.com,
	glaubitz@physik.fu-berlin.de, ysato@users.sourceforge.jp,
	dalias@libc.org, linux-snps-arc@lists.infradead.org,
	linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org,
	brads@mainlining.org
Subject: [PATCH v5 2/3] csky: Emulate two-byte cmpxchg
Date: Mon,  5 Oct 2026 12:05:55 +0000	[thread overview]
Message-ID: <20261005120556.383004-3-brads@mainlining.org> (raw)
In-Reply-To: <20261005120556.383004-1-brads@mainlining.org>

C-SKY has no two-byte atomic compare and swap, so the __cmpxchg()
macros let case 2 fall through to BUILD_BUG() via default, and a
two-byte cmpxchg() fails the build.

Route case 2 through the new cmpxchg_emu_u16(), which narrows the
old and new values itself, so all three orderings, relaxed, acquire
and full, keep the (uintptr_t) casts the case 1 path already uses.

Signed-off-by: Bradley Morgan <brads@mainlining.org>
---
 arch/csky/include/asm/cmpxchg.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/csky/include/asm/cmpxchg.h b/arch/csky/include/asm/cmpxchg.h
index db6dda47184e..6f3ca79e54ac 100644
--- a/arch/csky/include/asm/cmpxchg.h
+++ b/arch/csky/include/asm/cmpxchg.h
@@ -64,6 +64,9 @@
 	switch (size) {						\
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;							\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (unsigned long)__old, (unsigned long)__new); \
 		break;						\
 	case 4:							\
 		asm volatile (					\
@@ -97,6 +100,9 @@
 	switch (size) {						\
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;							\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (unsigned long)__old, (unsigned long)__new); \
 		break;						\
 	case 4:							\
 		asm volatile (					\
@@ -131,6 +137,9 @@
 	switch (size) {						\
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;							\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (unsigned long)__old, (unsigned long)__new); \
 		break;						\
 	case 4:							\
 		asm volatile (					\
-- 
2.53.0


WARNING: multiple messages have this Message-ID (diff)
From: Bradley Morgan <brads@mainlining.org>
To: akpm@linux-foundation.org, vgupta@kernel.org, guoren@kernel.org,
	chris@zankel.net, jcmvbkbc@gmail.com
Cc: arnd@arndb.de, paulmck@kernel.org, david.laight.linux@gmail.com,
	glaubitz@physik.fu-berlin.de, ysato@users.sourceforge.jp,
	dalias@libc.org, linux-snps-arc@lists.infradead.org,
	linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org,
	brads@mainlining.org
Subject: [PATCH v5 2/3] csky: Emulate two-byte cmpxchg
Date: Mon,  5 Oct 2026 12:05:55 +0000	[thread overview]
Message-ID: <20261005120556.383004-3-brads@mainlining.org> (raw)
In-Reply-To: <20261005120556.383004-1-brads@mainlining.org>

C-SKY has no two-byte atomic compare and swap, so the __cmpxchg()
macros let case 2 fall through to BUILD_BUG() via default, and a
two-byte cmpxchg() fails the build.

Route case 2 through the new cmpxchg_emu_u16(), which narrows the
old and new values itself, so all three orderings, relaxed, acquire
and full, keep the (uintptr_t) casts the case 1 path already uses.

Signed-off-by: Bradley Morgan <brads@mainlining.org>
---
 arch/csky/include/asm/cmpxchg.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/csky/include/asm/cmpxchg.h b/arch/csky/include/asm/cmpxchg.h
index db6dda47184e..6f3ca79e54ac 100644
--- a/arch/csky/include/asm/cmpxchg.h
+++ b/arch/csky/include/asm/cmpxchg.h
@@ -64,6 +64,9 @@
 	switch (size) {						\
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;							\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (unsigned long)__old, (unsigned long)__new); \
 		break;						\
 	case 4:							\
 		asm volatile (					\
@@ -97,6 +100,9 @@
 	switch (size) {						\
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;							\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (unsigned long)__old, (unsigned long)__new); \
 		break;						\
 	case 4:							\
 		asm volatile (					\
@@ -131,6 +137,9 @@
 	switch (size) {						\
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+		break;							\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (unsigned long)__old, (unsigned long)__new); \
 		break;						\
 	case 4:							\
 		asm volatile (					\
-- 
2.53.0

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  parent reply	other threads:[~2026-10-05 12:08 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-05 12:05 [PATCH v5 0/3] Add two-byte cmpxchg emulation and wire it into the architectures Bradley Morgan
2026-10-05 12:05 ` Bradley Morgan
2026-10-05 12:05 ` [PATCH v5 1/3] ARC: Emulate two-byte cmpxchg Bradley Morgan
2026-10-05 12:05   ` Bradley Morgan
2026-10-05 12:08   ` Bradley Morgan
2026-10-05 12:08     ` Bradley Morgan
2026-10-05 12:05 ` Bradley Morgan [this message]
2026-10-05 12:05   ` [PATCH v5 2/3] csky: " Bradley Morgan
2026-10-05 12:05 ` [PATCH v5 3/3] xtensa: " Bradley Morgan
2026-10-05 12:05   ` Bradley Morgan
  -- strict thread matches above, loose matches on Subject: below --
2026-10-05 12:06 [PATCH v5 0/3] Add two-byte cmpxchg emulation and wire it into the architectures Bradley Morgan
2026-10-05 12:06 ` [PATCH v5 2/3] csky: Emulate two-byte cmpxchg Bradley Morgan
2026-10-05 12:06   ` Bradley Morgan

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