net: enetc: add support for flow control

In the ENETC receive path, a frame received by the MAC is first stored
in a 256KB 'FIFO' memory, then transferred to DRAM when enqueuing it to
the RX ring. The FIFO is a shared resource for all ENETC ports, but
every port keeps track of its own memory utilization, on RX and on TX.

There is a setting for RX rings through which they can either operate in
'lossy' mode (where the lack of a free buffer causes an immediate
discard of the frame) or in 'lossless' mode (where the lack of a free
buffer in the ring makes the frame stay longer in the FIFO).

In turn, when the memory utilization of the FIFO exceeds a certain
margin, the MAC can be configured to emit PAUSE frames.

There is enough FIFO memory to buffer up to 3 MTU-sized frames per RX
port while not jeopardizing the other use cases (jumbo frames), and
also not consume bytes from the port TX allocations. Also, 3 MTU-sized
frames worth of memory is enough to ensure zero loss for 64 byte packets
at 1G line rate.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c b/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c
index 49835e878bbb..ebccaf02411c 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c
@@ -708,6 +708,22 @@ static int enetc_set_wol(struct net_device *dev,
 	return ret;
 }
 
+static void enetc_get_pauseparam(struct net_device *dev,
+				 struct ethtool_pauseparam *pause)
+{
+	struct enetc_ndev_priv *priv = netdev_priv(dev);
+
+	phylink_ethtool_get_pauseparam(priv->phylink, pause);
+}
+
+static int enetc_set_pauseparam(struct net_device *dev,
+				struct ethtool_pauseparam *pause)
+{
+	struct enetc_ndev_priv *priv = netdev_priv(dev);
+
+	return phylink_ethtool_set_pauseparam(priv->phylink, pause);
+}
+
 static int enetc_get_link_ksettings(struct net_device *dev,
 				    struct ethtool_link_ksettings *cmd)
 {
@@ -754,6 +770,8 @@ static const struct ethtool_ops enetc_pf_ethtool_ops = {
 	.get_ts_info = enetc_get_ts_info,
 	.get_wol = enetc_get_wol,
 	.set_wol = enetc_set_wol,
+	.get_pauseparam = enetc_get_pauseparam,
+	.set_pauseparam = enetc_set_pauseparam,
 };
 
 static const struct ethtool_ops enetc_vf_ethtool_ops = {