From 00b4c90787298349b799069360ced9ca843153dc Mon Sep 17 00:00:00 2001 From: Russell King Date: Thu, 1 Dec 2005 15:47:24 +0000 Subject: [ARM SMP] Use event instructions for spinlocks ARMv6K CPUs have SEV (send event) and WFE (wait for event) instructions which allow the CPU clock to be suspended until another CPU issues a SEV, rather than spinning on the lock wasting power. Make use of these instructions. Note that WFE does not wait if an event has been sent since the last WFE cleared the event status, so although it may look racy, the instruction implementation ensures that these are dealt with. Signed-off-by: Russell King --- include/asm-arm/spinlock.h | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/asm-arm/spinlock.h b/include/asm-arm/spinlock.h index 6ed4f916b16..43ad4e55878 100644 --- a/include/asm-arm/spinlock.h +++ b/include/asm-arm/spinlock.h @@ -30,6 +30,9 @@ static inline void __raw_spin_lock(raw_spinlock_t *lock) __asm__ __volatile__( "1: ldrex %0, [%1]\n" " teq %0, #0\n" +#ifdef CONFIG_CPU_32v6K +" wfene\n" +#endif " strexeq %0, %2, [%1]\n" " teqeq %0, #0\n" " bne 1b" @@ -65,7 +68,11 @@ static inline void __raw_spin_unlock(raw_spinlock_t *lock) smp_mb(); __asm__ __volatile__( -" str %1, [%0]" +" str %1, [%0]\n" +#ifdef CONFIG_CPU_32v6K +" mcr p15, 0, %1, c7, c10, 4\n" /* DSB */ +" sev" +#endif : : "r" (&lock->lock), "r" (0) : "cc"); @@ -87,6 +94,9 @@ static inline void __raw_write_lock(raw_rwlock_t *rw) __asm__ __volatile__( "1: ldrex %0, [%1]\n" " teq %0, #0\n" +#ifdef CONFIG_CPU_32v6K +" wfene\n" +#endif " strexeq %0, %2, [%1]\n" " teq %0, #0\n" " bne 1b" @@ -122,7 +132,11 @@ static inline void __raw_write_unlock(raw_rwlock_t *rw) smp_mb(); __asm__ __volatile__( - "str %1, [%0]" + "str %1, [%0]\n" +#ifdef CONFIG_CPU_32v6K +" mcr p15, 0, %1, c7, c10, 4\n" /* DSB */ +" sev\n" +#endif : : "r" (&rw->lock), "r" (0) : "cc"); @@ -148,6 +162,9 @@ static inline void __raw_read_lock(raw_rwlock_t *rw) "1: ldrex %0, [%2]\n" " adds %0, %0, #1\n" " strexpl %1, %0, [%2]\n" +#ifdef CONFIG_CPU_32v6K +" wfemi\n" +#endif " rsbpls %0, %1, #0\n" " bmi 1b" : "=&r" (tmp), "=&r" (tmp2) @@ -169,6 +186,11 @@ static inline void __raw_read_unlock(raw_rwlock_t *rw) " strex %1, %0, [%2]\n" " teq %1, #0\n" " bne 1b" +#ifdef CONFIG_CPU_32v6K +"\n cmp %0, #0\n" +" mcreq p15, 0, %0, c7, c10, 4\n" +" seveq" +#endif : "=&r" (tmp), "=&r" (tmp2) : "r" (&rw->lock) : "cc"); -- cgit v1.2.3 From 11849fe67430ba48547e17b25a7831da29863efa Mon Sep 17 00:00:00 2001 From: Arthur Othieno Date: Thu, 1 Dec 2005 20:58:01 +0000 Subject: [ARM] sema_count() removal sema_count() defined only for ARM but not used anywhere. Signed-off-by: Arthur Othieno Signed-off-by: Andrew Morton Signed-off-by: Russell King --- include/asm-arm/semaphore.h | 5 ----- 1 file changed, 5 deletions(-) (limited to 'include') diff --git a/include/asm-arm/semaphore.h b/include/asm-arm/semaphore.h index 71ca7d41268..d5dc624f452 100644 --- a/include/asm-arm/semaphore.h +++ b/include/asm-arm/semaphore.h @@ -47,11 +47,6 @@ static inline void init_MUTEX_LOCKED(struct semaphore *sem) sema_init(sem, 0); } -static inline int sema_count(struct semaphore *sem) -{ - return atomic_read(&sem->count); -} - /* * special register calling convention */ -- cgit v1.2.3