linux-kernel - [RFC PATCH 15/22] riscv: s64ilp32: Enable native atomic64

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Message-Id: <20230518131013.3366406-16-guoren@kernel.org>
Date:   Thu, 18 May 2023 09:10:06 -0400
From:   guoren@...nel.org
To:     arnd@...db.de, guoren@...nel.org, palmer@...osinc.com,
        tglx@...utronix.de, peterz@...radead.org, luto@...nel.org,
        conor.dooley@...rochip.com, heiko@...ech.de, jszhang@...nel.org,
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        jiawei@...as.ac.cn, liweiwei@...as.ac.cn, luxufan@...as.ac.cn,
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        jrtc27@...c27.com
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, Guo Ren <guoren@...ux.alibaba.com>
Subject: [RFC PATCH 15/22] riscv: s64ilp32: Enable native atomic64

From: Guo Ren <guoren@...ux.alibaba.com>

The traditional rv32 Linux (s32ilp32) uses a generic version of the
lib/atomic64.c, which are inaccurate atomic64 primitives and couldn't
co-work with READ_ONCE/WRITE_ONCE,  atomic_8/16/32. The s64ilp32 could
use native AMO instructions to implement accurate atomic64 primitives.

Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Signed-off-by: Guo Ren <guoren@...nel.org>
---
 arch/riscv/Kconfig              | 2 +-
 arch/riscv/include/asm/atomic.h | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 9c458496ec3a..33fe624ef6d3 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -60,7 +60,7 @@ config RISCV
 	select CPU_PM if CPU_IDLE
 	select EDAC_SUPPORT
 	select GENERIC_ARCH_TOPOLOGY
-	select GENERIC_ATOMIC64 if !64BIT
+	select GENERIC_ATOMIC64 if ARCH_RV32I
 	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_ENTRY
diff --git a/arch/riscv/include/asm/atomic.h b/arch/riscv/include/asm/atomic.h
index 0dfe9d857a76..edfa6a74fe04 100644
--- a/arch/riscv/include/asm/atomic.h
+++ b/arch/riscv/include/asm/atomic.h
@@ -16,6 +16,12 @@
 # endif
 #endif
 
+#ifdef CONFIG_ARCH_RV64ILP32
+typedef struct {
+	s64 counter;
+} atomic64_t;
+#endif
+
 #include <asm/cmpxchg.h>
 #include <asm/barrier.h>
 
-- 
2.36.1