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From:   Paul Burton <paul.burton@mips.com>
To:     "linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>
CC:     Huacai Chen <chenhc@lemote.com>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Paul Burton <pburton@wavecomp.com>
Subject: [PATCH 33/37] MIPS: barrier: Remove loongson_llsc_mb()
Thread-Topic: [PATCH 33/37] MIPS: barrier: Remove loongson_llsc_mb()
Thread-Index: AQHVd+QBGBvr0LXUB0q3rp1IZ4o/ww==
Date:   Mon, 30 Sep 2019 23:08:43 +0000
Message-ID: <20190930230806.2940505-34-paul.burton@mips.com>
References: <20190930230806.2940505-1-paul.burton@mips.com>
In-Reply-To: <20190930230806.2940505-1-paul.burton@mips.com>
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The loongson_llsc_mb() macro is no longer used - instead barriers are
emitted as part of inline asm using the __SYNC() macro. Remove the
now-defunct loongson_llsc_mb() macro.

Signed-off-by: Paul Burton <paul.burton@mips.com>
---

 arch/mips/include/asm/barrier.h | 40 ---------------------------------
 arch/mips/loongson64/Platform   |  2 +-
 2 files changed, 1 insertion(+), 41 deletions(-)

diff --git a/arch/mips/include/asm/barrier.h b/arch/mips/include/asm/barrie=
r.h
index c7e05e832da9..1a99a6c5b5dd 100644
--- a/arch/mips/include/asm/barrier.h
+++ b/arch/mips/include/asm/barrier.h
@@ -121,46 +121,6 @@ static inline void wmb(void)
 #define __smp_mb__before_atomic()	__smp_mb__before_llsc()
 #define __smp_mb__after_atomic()	smp_llsc_mb()
=20
-/*
- * Some Loongson 3 CPUs have a bug wherein execution of a memory access (l=
oad,
- * store or prefetch) in between an LL & SC can cause the SC instruction t=
o
- * erroneously succeed, breaking atomicity. Whilst it's unusual to write c=
ode
- * containing such sequences, this bug bites harder than we might otherwis=
e
- * expect due to reordering & speculation:
- *
- * 1) A memory access appearing prior to the LL in program order may actua=
lly
- *    be executed after the LL - this is the reordering case.
- *
- *    In order to avoid this we need to place a memory barrier (ie. a SYNC
- *    instruction) prior to every LL instruction, in between it and any ea=
rlier
- *    memory access instructions.
- *
- *    This reordering case is fixed by 3A R2 CPUs, ie. 3A2000 models and l=
ater.
- *
- * 2) If a conditional branch exists between an LL & SC with a target outs=
ide
- *    of the LL-SC loop, for example an exit upon value mismatch in cmpxch=
g()
- *    or similar, then misprediction of the branch may allow speculative
- *    execution of memory accesses from outside of the LL-SC loop.
- *
- *    In order to avoid this we need a memory barrier (ie. a SYNC instruct=
ion)
- *    at each affected branch target, for which we also use loongson_llsc_=
mb()
- *    defined below.
- *
- *    This case affects all current Loongson 3 CPUs.
- *
- * The above described cases cause an error in the cache coherence protoco=
l;
- * such that the Invalidate of a competing LL-SC goes 'missing' and SC
- * erroneously observes its core still has Exclusive state and lets the SC
- * proceed.
- *
- * Therefore the error only occurs on SMP systems.
- */
-#ifdef CONFIG_CPU_LOONGSON3_WORKAROUNDS /* Loongson-3's LLSC workaround */
-#define loongson_llsc_mb()	__asm__ __volatile__("sync" : : :"memory")
-#else
-#define loongson_llsc_mb()	do { } while (0)
-#endif
-
 static inline void sync_ginv(void)
 {
 	asm volatile(__SYNC(ginv, always));
diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Platform
index c1a4d4dc4665..28172500f95a 100644
--- a/arch/mips/loongson64/Platform
+++ b/arch/mips/loongson64/Platform
@@ -27,7 +27,7 @@ cflags-$(CONFIG_CPU_LOONGSON3)	+=3D -Wa,--trap
 #
 # Some versions of binutils, not currently mainline as of 2019/02/04, supp=
ort
 # an -mfix-loongson3-llsc flag which emits a sync prior to each ll instruc=
tion
-# to work around a CPU bug (see loongson_llsc_mb() in asm/barrier.h for a
+# to work around a CPU bug (see __SYNC_loongson3_war in asm/sync.h for a
 # description).
 #
 # We disable this in order to prevent the assembler meddling with the
--=20
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