work: new calculation of next tick

Changes method of calculation next work queue tick.
Instead of taking actual time of last tick, lets use
time of requested tick. From my experiments, it can
take up to ~40 cycles from requested time
of interrupt until interrupt handler is executed.

Signed-off-by: Tomasz Lauda <tomasz.lauda@linux.intel.com>

Author: tlauda

src/lib/work.c

@@ -69,13 +69,13 @@ struct work_queue {
 	struct notifier notifier;	/* notify CPU freq changes */
 	struct work_queue_timesource *ts;	/* time source for work queue */
 	uint32_t ticks_per_msec;	/* ticks per msec */
-	uint64_t run_ticks;	/* ticks when last run */
 	atomic_t num_work;	/* number of queued work items */
 };
 
 struct work_queue_shared_context {
 	atomic_t total_num_work;	/* number of total queued work items */
 	atomic_t timer_clients;		/* number of timer clients */
+	uint64_t last_tick;		/* time of last tick */
 
 	/* registered timers */
 	struct timer *timers[PLATFORM_CORE_COUNT];
@@ -104,6 +104,7 @@ static inline void work_set_timer(struct work_queue *queue)
 
 	if (atomic_add(&work_shared_ctx->total_num_work, 1) == 1) {
 		ticks = queue_calc_next_timeout(queue, work_get_timer(queue));
+		work_shared_ctx->last_tick = ticks;
 		queue->ts->timer_set(&queue->ts->timer, ticks);
 		atomic_add(&work_shared_ctx->timer_clients, 1);
 		timer_enable(&queue->ts->timer);
@@ -185,7 +186,7 @@ static inline void work_next_timeout(struct work_queue *queue,
 		work->timeout += next_d;
 	} else {
 		/* calc next run based on work request */
-		work->timeout = next_d + queue->run_ticks;
+		work->timeout = next_d + work_shared_ctx->last_tick;
 	}
 }
 
@@ -301,8 +302,10 @@ static void queue_reschedule(struct work_queue *queue)
 		/* re-arm only if there is work to do */
 		if (atomic_read(&work_shared_ctx->total_num_work)) {
 			/* re-arm timer */
-			ticks = queue_calc_next_timeout(queue,
-							queue->run_ticks);
+			ticks = queue_calc_next_timeout
+				(queue,
+				 work_shared_ctx->last_tick);
+			work_shared_ctx->last_tick = ticks;
 			queue->ts->timer_set(&queue->ts->timer, ticks);
 
 			queue_enable_registered_timers();
@@ -316,8 +319,6 @@ static void queue_run(void *data)
 	struct work_queue *queue = (struct work_queue *)data;
 	uint32_t flags;
 
-	queue->run_ticks = work_get_timer(queue);
-
 	timer_disable(&queue->ts->timer);
 
 	spin_lock_irq(&queue->lock, flags);