s390/qeth: add TX IRQ coalescing support for IQD devices

Since IQD devices complete (most of) their transmissions synchronously,
they don't offer TX completion IRQs and have no HW coalescing controls.
But we can fake the easy parts in SW, and give the user some control wrt
to how often the TX NAPI code should be triggered to process the TX
completions.

Having per-queue controls can in particular help the dedicated mcast
queue, as it likely benefits from different fine-tuning than what the
ucast queues need.

CC: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 75 insertions, 0 deletions

diff --git a/drivers/s390/net/qeth_ethtool.c b/drivers/s390/net/qeth_ethtool.c
index 6f0cc6fcc759..ebdc03210608 100644
--- a/drivers/s390/net/qeth_ethtool.c
+++ b/drivers/s390/net/qeth_ethtool.c
@@ -40,6 +40,7 @@ static const struct qeth_stats txq_stats[] = {
 	QETH_TXQ_STAT("Packing mode switches", packing_mode_switch),
 	QETH_TXQ_STAT("Queue stopped", stopped),
 	QETH_TXQ_STAT("Doorbell", doorbell),
+	QETH_TXQ_STAT("IRQ for frames", coal_frames),
 	QETH_TXQ_STAT("Completion yield", completion_yield),
 	QETH_TXQ_STAT("Completion timer", completion_timer),
 };
@@ -109,6 +110,38 @@ static void qeth_get_ethtool_stats(struct net_device *dev,
 				   txq_stats, TXQ_STATS_LEN);
 }
 
+static void __qeth_set_coalesce(struct net_device *dev,
+				struct qeth_qdio_out_q *queue,
+				struct ethtool_coalesce *coal)
+{
+	WRITE_ONCE(queue->coalesce_usecs, coal->tx_coalesce_usecs);
+	WRITE_ONCE(queue->max_coalesced_frames, coal->tx_max_coalesced_frames);
+
+	if (coal->tx_coalesce_usecs &&
+	    netif_running(dev) &&
+	    !qeth_out_queue_is_empty(queue))
+		qeth_tx_arm_timer(queue, coal->tx_coalesce_usecs);
+}
+
+static int qeth_set_coalesce(struct net_device *dev,
+			     struct ethtool_coalesce *coal)
+{
+	struct qeth_card *card = dev->ml_priv;
+	struct qeth_qdio_out_q *queue;
+	unsigned int i;
+
+	if (!IS_IQD(card))
+		return -EOPNOTSUPP;
+
+	if (!coal->tx_coalesce_usecs && !coal->tx_max_coalesced_frames)
+		return -EINVAL;
+
+	qeth_for_each_output_queue(card, queue, i)
+		__qeth_set_coalesce(dev, queue, coal);
+
+	return 0;
+}
+
 static void qeth_get_ringparam(struct net_device *dev,
 			       struct ethtool_ringparam *param)
 {
@@ -244,6 +277,43 @@ static int qeth_set_tunable(struct net_device *dev,
 	}
 }
 
+static int qeth_get_per_queue_coalesce(struct net_device *dev, u32 __queue,
+				       struct ethtool_coalesce *coal)
+{
+	struct qeth_card *card = dev->ml_priv;
+	struct qeth_qdio_out_q *queue;
+
+	if (!IS_IQD(card))
+		return -EOPNOTSUPP;
+
+	if (__queue >= card->qdio.no_out_queues)
+		return -EINVAL;
+
+	queue = card->qdio.out_qs[__queue];
+
+	coal->tx_coalesce_usecs = queue->coalesce_usecs;
+	coal->tx_max_coalesced_frames = queue->max_coalesced_frames;
+	return 0;
+}
+
+static int qeth_set_per_queue_coalesce(struct net_device *dev, u32 queue,
+				       struct ethtool_coalesce *coal)
+{
+	struct qeth_card *card = dev->ml_priv;
+
+	if (!IS_IQD(card))
+		return -EOPNOTSUPP;
+
+	if (queue >= card->qdio.no_out_queues)
+		return -EINVAL;
+
+	if (!coal->tx_coalesce_usecs && !coal->tx_max_coalesced_frames)
+		return -EINVAL;
+
+	__qeth_set_coalesce(dev, card->qdio.out_qs[queue], coal);
+	return 0;
+}
+
 /* Helper function to fill 'advertising' and 'supported' which are the same. */
 /* Autoneg and full-duplex are supported and advertised unconditionally.     */
 /* Always advertise and support all speeds up to specified, and only one     */
@@ -443,7 +513,10 @@ static int qeth_get_link_ksettings(struct net_device *netdev,
 }
 
 const struct ethtool_ops qeth_ethtool_ops = {
+	.supported_coalesce_params = ETHTOOL_COALESCE_TX_USECS |
+				     ETHTOOL_COALESCE_TX_MAX_FRAMES,
 	.get_link = ethtool_op_get_link,
+	.set_coalesce = qeth_set_coalesce,
 	.get_ringparam = qeth_get_ringparam,
 	.get_strings = qeth_get_strings,
 	.get_ethtool_stats = qeth_get_ethtool_stats,
@@ -454,6 +527,8 @@ const struct ethtool_ops qeth_ethtool_ops = {
 	.get_ts_info = qeth_get_ts_info,
 	.get_tunable = qeth_get_tunable,
 	.set_tunable = qeth_set_tunable,
+	.get_per_queue_coalesce = qeth_get_per_queue_coalesce,
+	.set_per_queue_coalesce = qeth_set_per_queue_coalesce,
 	.get_link_ksettings = qeth_get_link_ksettings,
 };