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, 16 insertions, 0 deletions

diff --git a/drivers/s390/net/qeth_ethtool.c b/drivers/s390/net/qeth_ethtool.c
index 93a53fed4cf8..a443e5f86ab7 100644
--- a/drivers/s390/net/qeth_ethtool.c
+++ b/drivers/s390/net/qeth_ethtool.c
@@ -154,6 +154,21 @@ static void qeth_get_drvinfo(struct net_device *dev,
 		 CARD_RDEV_ID(card), CARD_WDEV_ID(card), CARD_DDEV_ID(card));
 }
 
+static void qeth_get_channels(struct net_device *dev,
+			      struct ethtool_channels *channels)
+{
+	struct qeth_card *card = dev->ml_priv;
+
+	channels->max_rx = dev->num_rx_queues;
+	channels->max_tx = card->qdio.no_out_queues;
+	channels->max_other = 0;
+	channels->max_combined = 0;
+	channels->rx_count = dev->real_num_rx_queues;
+	channels->tx_count = dev->real_num_tx_queues;
+	channels->other_count = 0;
+	channels->combined_count = 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     */
@@ -359,6 +374,7 @@ const struct ethtool_ops qeth_ethtool_ops = {
 	.get_ethtool_stats = qeth_get_ethtool_stats,
 	.get_sset_count = qeth_get_sset_count,
 	.get_drvinfo = qeth_get_drvinfo,
+	.get_channels = qeth_get_channels,
 	.get_link_ksettings = qeth_get_link_ksettings,
 };