net: ipa: rework last transaction determination

When quiescing a channel, we find the "last" transaction, which is
the latest one to have been allocated.  (New transaction allocation
will have been prevented by the time this is called.)

Currently we do this by looking for the first non-empty transaction
list in each state, then return the last entry from that last.
Instead, determine the last entry in each list (if any) and return
that entry if found.

Temporarily (locally) introduce list_last_entry_or_null() as a
helper for this, mirroring list_first_entry_or_null().  This macro
definition will be removed by an upcoming patch.

Remove the temporary warnings added by the previous commit.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 14 deletions

diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index 9e307eebd33f..0ea98fa5dee5 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -710,7 +710,6 @@ static void gsi_evt_ring_program(struct gsi *gsi, u32 evt_ring_id)
 static struct gsi_trans *gsi_channel_trans_last(struct gsi_channel *channel)
 {
 	struct gsi_trans_info *trans_info = &channel->trans_info;
-	const struct list_head *list;
 	struct gsi_trans *trans;
 
 	spin_lock_bh(&trans_info->spinlock);
@@ -719,29 +718,30 @@ static struct gsi_trans *gsi_channel_trans_last(struct gsi_channel *channel)
 	 * before we disabled transmits, so check for that.
 	 */
 	if (channel->toward_ipa) {
-		list = &trans_info->alloc;
-		if (!list_empty(list))
+		trans = list_last_entry_or_null(&trans_info->alloc,
+						struct gsi_trans, links);
+		if (trans)
 			goto done;
-		list = &trans_info->committed;
-		if (!list_empty(list))
+		trans = list_last_entry_or_null(&trans_info->committed,
+						struct gsi_trans, links);
+		if (trans)
 			goto done;
-		list = &trans_info->pending;
-		if (!list_empty(list))
+		trans = list_last_entry_or_null(&trans_info->pending,
+						struct gsi_trans, links);
+		if (trans)
 			goto done;
 	}
 
 	/* Otherwise (TX or RX) we want to wait for anything that
 	 * has completed, or has been polled but not released yet.
 	 */
-	list = &trans_info->complete;
-	if (!list_empty(list))
+	trans = list_last_entry_or_null(&trans_info->complete,
+					struct gsi_trans, links);
+	if (trans)
 		goto done;
-	list = &trans_info->polled;
-	if (list_empty(list))
-		list = NULL;
+	trans = list_last_entry_or_null(&trans_info->polled,
+					struct gsi_trans, links);
 done:
-	trans = list ? list_last_entry(list, struct gsi_trans, links) : NULL;
-
 	/* Caller will wait for this, so take a reference */
 	if (trans)
 		refcount_inc(&trans->refcount);