diff options
Diffstat (limited to 'bsps/no_cpu/no_bsp/mpci/lock.c')
-rw-r--r-- | bsps/no_cpu/no_bsp/mpci/lock.c | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/bsps/no_cpu/no_bsp/mpci/lock.c b/bsps/no_cpu/no_bsp/mpci/lock.c new file mode 100644 index 0000000000..5b53df8d38 --- /dev/null +++ b/bsps/no_cpu/no_bsp/mpci/lock.c @@ -0,0 +1,84 @@ +/* Shared Memory Lock Routines + * + * This shared memory locked queue support routine need to be + * able to lock the specified locked queue. Interrupts are + * disabled while the queue is locked to prevent preemption + * and deadlock when two tasks poll for the same lock. + * previous level. + * + * COPYRIGHT (c) 1989-1999. + * On-Line Applications Research Corporation (OAR). + * + * The license and distribution terms for this file may be + * found in the file LICENSE in this distribution or at + * http://www.rtems.org/license/LICENSE. + */ + +#include <rtems.h> +#include <bsp.h> +#include <shm_driver.h> + +/* + * Shm_Initialize_lock + * + * Initialize the lock for the specified locked queue. + */ + +void Shm_Initialize_lock( + Shm_Locked_queue_Control *lq_cb +) +{ + lq_cb->lock = LQ_UNLOCKED; +} + +/* void _Shm_Lock( &lq_cb ) + * + * This shared memory locked queue support routine locks the + * specified locked queue. It disables interrupts to prevent + * a deadlock condition. + */ + +void Shm_Lock( + Shm_Locked_queue_Control *lq_cb +) +{ + uint32_t isr_level; + uint32_t *lockptr = (uint32_t*) &lq_cb->lock; + uint32_t lock_value; + + lock_value = 0x80000000; + rtems_interrupt_disable( isr_level ); + + Shm_isrstat = isr_level; + while ( lock_value ) { + __asm__ volatile( "" + : "=r" (lockptr), "=r" (lock_value) + : "0" (lockptr), "1" (lock_value) + ); + /* + * If not available, then may want to delay to reduce load on lock. + * + * NOTE: BSP must initialize the counter facility. Delay value is BSP + * dependent. + */ + if ( lock_value ) + rtems_counter_delay_nanoseconds( 100 ); + } +} + +/* + * Shm_Unlock + * + * Unlock the lock for the specified locked queue. + */ + +void Shm_Unlock( + Shm_Locked_queue_Control *lq_cb +) +{ + uint32_t isr_level; + + lq_cb->lock = SHM_UNLOCK_VALUE; + isr_level = Shm_isrstat; + rtems_interrupt_enable( isr_level ); +} |