gpu: nvgpu: fix event id polling

In gk20a_event_id_poll(), we always set the mask value
and return it. This causes poll() from UMD to be always
successful irrespective of event is really generated or not

Fix this by adding a flag event_posted for each event
Set this flag while posting the event
In gk20a_event_id_poll(), set the mask value only if
this flag is set. If flag is set, set mask and clear the flag

Bug 200089620

Change-Id: If14236547c611fe4bfa1410ff5b69c9fa02d43bb
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/1160253
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>

drivers/gpu/nvgpu/gk20a/channel_gk20a.c

@@ -2519,18 +2519,25 @@ static unsigned int gk20a_event_id_poll(struct file *filep, poll_table *wait)
 	if (event_id_data->is_tsg) {
 		struct tsg_gk20a *tsg = g->fifo.tsg + event_id_data->id;
 
+		if (event_id_data->event_posted) {
 			gk20a_dbg_info(
 				"found pending event_id=%d on TSG=%d\n",
 				event_id, tsg->tsgid);
+			mask = (POLLPRI | POLLIN);
+			event_id_data->event_posted = false;
+		}
 	} else {
 		struct channel_gk20a *ch = g->fifo.channel
 					   + event_id_data->id;
 
+		if (event_id_data->event_posted) {
 			gk20a_dbg_info(
 				"found pending event_id=%d on chid=%d\n",
 				event_id, ch->hw_chid);
-	}
 			mask = (POLLPRI | POLLIN);
+			event_id_data->event_posted = false;
+		}
+	}
 
 	mutex_unlock(&event_id_data->lock);
 
@@ -2609,6 +2616,7 @@ void gk20a_channel_event_id_post_event(struct channel_gk20a *ch,
 	gk20a_dbg_info(
 		"posting event for event_id=%d on ch=%d\n",
 		event_id, ch->hw_chid);
+	event_id_data->event_posted = true;
 
 	wake_up_interruptible_all(&event_id_data->event_id_wq);
 

drivers/gpu/nvgpu/gk20a/channel_gk20a.h

@@ -84,6 +84,8 @@ struct gk20a_event_id_data {
 	bool is_tsg;
 	u32 event_id;
 
+	bool event_posted;
+
 	wait_queue_head_t event_id_wq;
 	struct mutex lock;
 	struct list_head event_id_node;

drivers/gpu/nvgpu/gk20a/tsg_gk20a.c

@@ -231,6 +231,7 @@ void gk20a_tsg_event_id_post_event(struct tsg_gk20a *tsg,
 	gk20a_dbg_info(
 		"posting event for event_id=%d on tsg=%d\n",
 		event_id, tsg->tsgid);
+	event_id_data->event_posted = true;
 
 	wake_up_interruptible_all(&event_id_data->event_id_wq);