[PATCH 6/9] net: ethernet: ti: cpts: clean up event list if event pool is empty

[Grygorii Strashko <grygorii.strashko@ti.com>]

From: WingMan Kwok <w-kwok2@ti.com>

When a CPTS user does not exit gracefully by disabling cpts
timestamping and leaving a joined multicast group, the system
continues to receive and timestamps the ptp packets which eventually
occupy all the event list entries.  When this happns, the added code
tries to remove some list entries which are expired.

Signed-off-by: WingMan Kwok <w-kwok2@ti.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
 drivers/net/ethernet/ti/cpts.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ti/cpts.c b/drivers/net/ethernet/ti/cpts.c
index 970d4e2..ff8bb85 100644
--- a/drivers/net/ethernet/ti/cpts.c
+++ b/drivers/net/ethernet/ti/cpts.c
@@ -57,22 +57,48 @@ static int cpts_fifo_pop(struct cpts *cpts, u32 *high, u32 *low)
 	return -1;
 }
 
+static int cpts_event_list_clean_up(struct cpts *cpts)
+{
+	struct list_head *this, *next;
+	struct cpts_event *event;
+	int removed = 0;
+
+	list_for_each_safe(this, next, &cpts->events) {
+		event = list_entry(this, struct cpts_event, list);
+		if (event_expired(event)) {
+			list_del_init(&event->list);
+			list_add(&event->list, &cpts->pool);
+			++removed;
+		}
+	}
+	return removed;
+}
+
 /*
  * Returns zero if matching event type was found.
  */
 static int cpts_fifo_read(struct cpts *cpts, int match)
 {
 	int i, type = -1;
+	int removed;
 	u32 hi, lo;
 	struct cpts_event *event;
 
 	for (i = 0; i < CPTS_FIFO_DEPTH; i++) {
 		if (cpts_fifo_pop(cpts, &hi, &lo))
 			break;
+
 		if (list_empty(&cpts->pool)) {
-			pr_err("cpts: event pool is empty\n");
-			return -1;
+			removed = cpts_event_list_clean_up(cpts);
+			if (!removed) {
+				dev_err(cpts->dev,
+					"cpts: event pool is empty\n");
+				return -1;
+			}
+			dev_dbg(cpts->dev,
+				"cpts: event pool cleaned up %d\n", removed);
 		}
+
 		event = list_first_entry(&cpts->pool, struct cpts_event, list);
 		event->tmo = jiffies + 2;
 		event->high = hi;
-- 
2.9.3