[Skiboot] [PATCH v2 1/3] hw/bt: Fix bt_add_ipmi_msg_head() logic

[Vasant Hegde]

BT send logic always sends top of bt message list to BMC. Once BMC reads the
message, it clears the interrupt and bt_idle() becomes true.

bt_add_ipmi_msg_head() adds message to top of the list. If bt message list
is not empty then:
  - if bt_idle() is true then we will endup sending message to BMC before
    getting response from BMC for inflight message. Looks like on some
    BMC implementation this results in message timeout.
  - else we endup starting message timer without actually sending message
    to BMC.. which is not correct.

This patch fixes above described issue by adding message to right place
in the list.

Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
---
Stewart,
  All I'm doing is list_pop/list_add. May be we can have new function
  (list_add_after()>. Let me know whether you are ok with this patch
   -OR- want me to add list_add_after()>

-Vasant

 hw/bt.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/hw/bt.c b/hw/bt.c
index 5a6bc3cde..a3561953b 100644
--- a/hw/bt.c
+++ b/hw/bt.c
@@ -533,11 +533,20 @@ static void bt_add_msg(struct bt_msg *bt_msg)
 
 static int bt_add_ipmi_msg_head(struct ipmi_msg *ipmi_msg)
 {
+	struct bt_msg *tmp_bt_msg;
 	struct bt_msg *bt_msg = container_of(ipmi_msg, struct bt_msg, ipmi_msg);
 
 	lock(&bt.lock);
 	bt_add_msg(bt_msg);
-	list_add(&bt.msgq, &bt_msg->link);
+
+	if (list_empty(&bt.msgq)) {
+		list_add(&bt.msgq, &bt_msg->link);
+	} else {
+		/* Add message after top message */
+		tmp_bt_msg = list_pop(&bt.msgq, struct bt_msg, link);
+		list_add(&bt.msgq, &bt_msg->link);
+		list_add(&bt.msgq, &tmp_bt_msg->link);
+	}
 	bt_send_and_unlock();
 
 	return 0;
-- 
2.14.3