cortex-m: Add task_wait_event_mask() helper function

BUG=chrome-os-partner:27180
BRANCH=rambi
TEST=Tested indirectly via subsequent patches to use
this call in the adc and i2c handlers for the lm4.

Change-Id: I53501fdf47d606ea6c7705facb66e945e25d9745
Signed-off-by: Dave Parker <dparker@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/191300
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>

2 files changed, 49 insertions, 1 deletions

diff --git a/core/cortex-m/task.c b/core/cortex-m/task.c
index 5e309ef4cb..5d2f967693 100644
--- a/core/cortex-m/task.c
+++ b/core/cortex-m/task.c
@@ -380,6 +380,35 @@ uint32_t task_wait_event(int timeout_us)
 	return __wait_evt(timeout_us, TASK_ID_IDLE);
 }
 
+uint32_t task_wait_event_mask(uint32_t event_mask, int timeout_us)
+{
+	uint64_t deadline = get_time().val + timeout_us;
+	uint32_t events = 0;
+	int time_remaining_us = timeout_us;
+
+	/* Add the timer event to the mask so we can indicate a timeout */
+	event_mask |= TASK_EVENT_TIMER;
+
+	while (!(events & event_mask)) {
+		/* Collect events to re-post later */
+		events |= __wait_evt(time_remaining_us, TASK_ID_IDLE);
+
+		time_remaining_us = deadline - get_time().val;
+		if (timeout_us > 0 && time_remaining_us <= 0) {
+			/* Ensure we return a TIMER event if we timeout */
+			events |= TASK_EVENT_TIMER;
+			break;
+		}
+	}
+
+	/* Re-post any other events collected */
+	if (events & ~event_mask)
+		atomic_or(task_get_event_bitmap(task_get_current()),
+			  events & ~event_mask);
+
+	return events & event_mask;
+}
+
 void task_enable_irq(int irq)
 {
 	CPU_NVIC_EN(irq / 32) = 1 << (irq % 32);
diff --git a/include/task.h b/include/task.h
index 723c6f0ad6..6b10c649b1 100644
--- a/include/task.h
+++ b/include/task.h
@@ -95,10 +95,29 @@ uint32_t *task_get_event_bitmap(task_id_t tskid);
  * @param timeout_us	If > 0, sets a timer to produce the TASK_EVENT_TIMER
  *			event after the specified micro-second duration.
  *
- * @return The bitmap of received events. */
+ * @return The bitmap of received events.
+ */
 uint32_t task_wait_event(int timeout_us);
 
 /**
+ * Wait for any event included in an event mask.
+ *
+ * If one or more events are already pending, returns immediately.  Otherwise,
+ * it de-schedules the calling task and wakes up the next one in the priority
+ * order.  Automatically clears the bitmap of received events before returning
+ * the events which are set.
+ *
+ * @param event_mask	Bitmap of task events to wait for.
+ *
+ * @param timeout_us	If > 0, sets a timer to produce the TASK_EVENT_TIMER
+ *			event after the specified micro-second duration.
+ *
+ * @return		The bitmap of received events. Includes
+ *			TASK_EVENT_TIMER if the timeout is reached.
+ */
+uint32_t task_wait_event_mask(uint32_t event_mask, int timeout_us);
+
+/**
  * Prints the list of tasks.
  *
  * Uses the command output channel.  May be called from interrupt level.