s390/qeth: add TX multiqueue support for IQD devices

qeth has been supporting multiple HW Output Queues for a long time. But
rather than exposing those queues to the stack, it uses its own queue
selection logic in .ndo_start_xmit... with all the drawbacks that
entails.
Start off by switching IQD devices over to a proper mqs net_device,
and converting all the netdev_queue management code.

One oddity with IQD devices is the requirement to place all mcast
traffic on the _highest_ established HW queue. Doing so via
.ndo_select_queue seems straight-forward - but that won't work if only
some of the HW queues are active
(ie. when dev->real_num_tx_queues < dev->num_tx_queues), since
netdev_cap_txqueue() will not allow us to put skbs on the higher queues.

To make this work, we
1. let .ndo_select_queue() map all mcast traffic to netdev_queue 0, and
2. later re-map the netdev_queue and HW queue indices in
   .ndo_start_xmit and the TX completion handler.

With this patch we default to a fixed set of 1 ucast and 1 mcast queue.
Support for dynamic reconfiguration is added at a later time.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 3 deletions

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index 730930135aba..836cde67f367 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -219,6 +219,9 @@ static inline int qeth_is_ipa_enabled(struct qeth_ipa_info *ipa,
 /* QDIO queue and buffer handling                                            */
 /*****************************************************************************/
 #define QETH_MAX_QUEUES 4
+#define QETH_IQD_MIN_TXQ	2	/* One for ucast, one for mcast. */
+#define QETH_IQD_MCAST_TXQ	0
+#define QETH_IQD_MIN_UCAST_TXQ	1
 #define QETH_IN_BUF_SIZE_DEFAULT 65536
 #define QETH_IN_BUF_COUNT_DEFAULT 64
 #define QETH_IN_BUF_COUNT_HSDEFAULT 128
@@ -835,6 +838,15 @@ static inline bool qeth_netdev_is_registered(struct net_device *dev)
 	return dev->netdev_ops != NULL;
 }
 
+static inline u16 qeth_iqd_translate_txq(struct net_device *dev, u16 txq)
+{
+	if (txq == QETH_IQD_MCAST_TXQ)
+		return dev->num_tx_queues - 1;
+	if (txq == dev->num_tx_queues - 1)
+		return QETH_IQD_MCAST_TXQ;
+	return txq;
+}
+
 static inline void qeth_scrub_qdio_buffer(struct qdio_buffer *buf,
 					  unsigned int elements)
 {
@@ -934,10 +946,8 @@ int qeth_get_priority_queue(struct qeth_card *card, struct sk_buff *skb,
 			    int ipv);
 static inline struct qeth_qdio_out_q *qeth_get_tx_queue(struct qeth_card *card,
 							struct sk_buff *skb,
-							int ipv, int cast_type)
+							int ipv)
 {
-	if (IS_IQD(card) && cast_type != RTN_UNICAST)
-		return card->qdio.out_qs[card->qdio.no_out_queues - 1];
 	if (!card->qdio.do_prio_queueing)
 		return card->qdio.out_qs[card->qdio.default_out_queue];
 	return card->qdio.out_qs[qeth_get_priority_queue(card, skb, ipv)];
@@ -1022,6 +1032,8 @@ netdev_features_t qeth_features_check(struct sk_buff *skb,
 				      struct net_device *dev,
 				      netdev_features_t features);
 void qeth_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats);
+u16 qeth_iqd_select_queue(struct net_device *dev, struct sk_buff *skb,
+			  u8 cast_type, struct net_device *sb_dev);
 int qeth_open(struct net_device *dev);
 int qeth_stop(struct net_device *dev);