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MIPS: atomic: Emit Loongson3 sync workarounds within asm

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Generate the sync instructions required to workaround Loongson3 LL/SC
errata within inline asm blocks, which feels a little safer than doing
it from C where strictly speaking the compiler would be well within its
rights to insert a memory access between the separate asm statements we
previously had, containing sync & ll instructions respectively.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: linux-kernel@vger.kernel.org
This commit is contained in:
Paul Burton 2019-10-01 21:53:20 +00:00
parent a38ee6bb14
commit 4d1dbfe6cb
No known key found for this signature in database
GPG key ID: 3EA79FACB57500DD
1 changed files with 14 additions and 6 deletions
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20
arch/mips/include/asm/atomic.h
View file

@ -21,6 +21,7 @@
#include <asm/cpu-features.h>
#include <asm/cmpxchg.h>
#include <asm/llsc.h>
#include <asm/sync.h>
#include <asm/war.h>
#define ATOMIC_INIT(i) { (i) }
@ -56,10 +57,10 @@ static __inline__ void pfx##_##op(type i, pfx##_t * v) \
return; \
} \
\
loongson_llsc_mb(); \
__asm__ __volatile__( \
" .set push \n" \
" .set " MIPS_ISA_LEVEL " \n" \
" " __SYNC(full, loongson3_war) " \n" \
"1: " #ll " %0, %1 # " #pfx "_" #op " \n" \
" " #asm_op " %0, %2 \n" \
" " #sc " %0, %1 \n" \
@ -85,10 +86,10 @@ static __inline__ type pfx##_##op##_return_relaxed(type i, pfx##_t * v) \
return result; \
} \
\
loongson_llsc_mb(); \
__asm__ __volatile__( \
" .set push \n" \
" .set " MIPS_ISA_LEVEL " \n" \
" " __SYNC(full, loongson3_war) " \n" \
"1: " #ll " %1, %2 # " #pfx "_" #op "_return\n" \
" " #asm_op " %0, %1, %3 \n" \
" " #sc " %0, %2 \n" \
@ -117,10 +118,10 @@ static __inline__ type pfx##_fetch_##op##_relaxed(type i, pfx##_t * v) \
return result; \
} \
\
loongson_llsc_mb(); \
__asm__ __volatile__( \
" .set push \n" \
" .set " MIPS_ISA_LEVEL " \n" \
" " __SYNC(full, loongson3_war) " \n" \
"1: " #ll " %1, %2 # " #pfx "_fetch_" #op "\n" \
" " #asm_op " %0, %1, %3 \n" \
" " #sc " %0, %2 \n" \
@ -200,10 +201,10 @@ static __inline__ int atomic_sub_if_positive(int i, atomic_t * v)
if (kernel_uses_llsc) {
int temp;
loongson_llsc_mb();
__asm__ __volatile__(
" .set push \n"
" .set "MIPS_ISA_LEVEL" \n"
" " __SYNC(full, loongson3_war) " \n"
"1: ll %1, %2 # atomic_sub_if_positive\n"
" .set pop \n"
" subu %0, %1, %3 \n"
@ -213,7 +214,7 @@ static __inline__ int atomic_sub_if_positive(int i, atomic_t * v)
" .set "MIPS_ISA_LEVEL" \n"
" sc %1, %2 \n"
"\t" __SC_BEQZ "%1, 1b \n"
"2: \n"
"2: " __SYNC(full, loongson3_war) " \n"
" .set pop \n"
: "=&r" (result), "=&r" (temp),
"+" GCC_OFF_SMALL_ASM() (v->counter)
@ -229,7 +230,14 @@ static __inline__ int atomic_sub_if_positive(int i, atomic_t * v)
raw_local_irq_restore(flags);
}
smp_llsc_mb();
/*
* In the Loongson3 workaround case we already have a completion
* barrier at 2: above, which is needed due to the bltz that can branch
* to code outside of the LL/SC loop. As such, we don't need to emit
* another barrier here.
*/
if (!__SYNC_loongson3_war)
smp_llsc_mb();
return result;
}