[PATCH net-next 5/5] net: enetc: add support for flow control

Vladimir Oltean
2021-04-16T23:43:50Z

From: Vladimir Oltean <vladimir.oltean@nxp.com>

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>
---
.../ethernet/freescale/enetc/enetc_ethtool.c | 18 ++++++
.../net/ethernet/freescale/enetc/enetc_hw.h | 9 +++
.../net/ethernet/freescale/enetc/enetc_pf.c | 60 ++++++++++++++++++-
3 files changed, 85 insertions(+), 2 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 = {
diff --git a/drivers/net/ethernet/freescale/enetc/enetc_hw.h b/drivers/net/ethernet/freescale/enetc/enetc_hw.h
index 04ac7fc23ead..0f5f081a5baf 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_hw.h
+++ b/drivers/net/ethernet/freescale/enetc/enetc_hw.h
@@ -109,6 +109,7 @@ enum enetc_bdr_type {TX, RX};
/* RX BDR reg offsets */
#define ENETC_RBMR 0
#define ENETC_RBMR_BDS BIT(2)
+#define ENETC_RBMR_CM BIT(4)
#define ENETC_RBMR_VTE BIT(5)
#define ENETC_RBMR_EN BIT(31)
#define ENETC_RBSR 0x4
@@ -180,6 +181,8 @@ enum enetc_bdr_type {TX, RX};
#define ENETC_PSIVLANR(n) (0x0240 + (n) * 4) /* n = SI index */
#define ENETC_PSIVLAN_EN BIT(31)
#define ENETC_PSIVLAN_SET_QOS(val) ((u32)(val) << 12)
+#define ENETC_PPAUONTR 0x0410
+#define ENETC_PPAUOFFTR 0x0414
#define ENETC_PTXMBAR 0x0608
#define ENETC_PCAPR0 0x0900
#define ENETC_PCAPR0_RXBDR(val) ((val) >> 24)
@@ -227,6 +230,7 @@ enum enetc_bdr_type {TX, RX};
#define ENETC_PM0_TX_EN BIT(0)
#define ENETC_PM0_RX_EN BIT(1)
#define ENETC_PM0_PROMISC BIT(4)
+#define ENETC_PM0_PAUSE_IGN BIT(8)
#define ENETC_PM0_CMD_XGLP BIT(10)
#define ENETC_PM0_CMD_TXP BIT(11)
#define ENETC_PM0_CMD_PHY_TX_EN BIT(15)
@@ -239,6 +243,11 @@ enum enetc_bdr_type {TX, RX};

#define ENETC_PM_IMDIO_BASE 0x8030

+#define ENETC_PM0_PAUSE_QUANTA 0x8054
+#define ENETC_PM0_PAUSE_THRESH 0x8064
+#define ENETC_PM1_PAUSE_QUANTA 0x9054
+#define ENETC_PM1_PAUSE_THRESH 0x9064
+
#define ENETC_PM0_SINGLE_STEP 0x80c0
#define ENETC_PM1_SINGLE_STEP 0x90c0
#define ENETC_PM0_SINGLE_STEP_CH BIT(7)
diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pf.c b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
index 1ae2473cbc16..aff1339442cc 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_pf.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
@@ -1015,7 +1015,12 @@ static void enetc_pl_mac_link_up(struct phylink_config *config,
int duplex, bool tx_pause, bool rx_pause)
{
struct enetc_pf *pf = phylink_to_enetc_pf(config);
+ u32 pause_off_thresh = 0, pause_on_thresh = 0;
+ u32 init_quanta = 0, refresh_quanta = 0;
+ struct enetc_hw *hw = &pf->si->hw;
struct enetc_ndev_priv *priv;
+ u32 rbmr, cmd_cfg;
+ int idx;

priv = netdev_priv(pf->si->ndev);
if (priv->active_offloads & ENETC_F_QBV)
@@ -1023,9 +1028,60 @@ static void enetc_pl_mac_link_up(struct phylink_config *config,

if (!phylink_autoneg_inband(mode) &&
phy_interface_mode_is_rgmii(interface))
- enetc_force_rgmii_mac(&pf->si->hw, speed, duplex);
+ enetc_force_rgmii_mac(hw, speed, duplex);
+
+ /* Flow control */
+ for (idx = 0; idx < priv->num_rx_rings; idx++) {
+ rbmr = enetc_rxbdr_rd(hw, idx, ENETC_RBMR);
+
+ if (tx_pause)
+ rbmr |= ENETC_RBMR_CM;
+ else
+ rbmr &= ~ENETC_RBMR_CM;
+
+ enetc_rxbdr_wr(hw, idx, ENETC_RBMR, rbmr);
+ }
+
+ if (tx_pause) {
+ /* When the port first enters congestion, send a PAUSE request
+ * with the maximum number of quanta. When the port exits
+ * congestion, it will automatically send a PAUSE frame with
+ * zero quanta.
+ */
+ init_quanta = 0xffff;
+
+ /* Also, set up the refresh timer to send follow-up PAUSE
+ * frames at half the quanta value, in case the congestion
+ * condition persists.
+ */
+ refresh_quanta = 0xffff / 2;
+
+ /* Start emitting PAUSE frames when 3 large frames (or more
+ * smaller frames) have accumulated in the FIFO waiting to be
+ * DMAed to the RX ring.
+ */
+ pause_on_thresh = 3 * ENETC_MAC_MAXFRM_SIZE;
+ pause_off_thresh = 1 * ENETC_MAC_MAXFRM_SIZE;
+ }
+
+ enetc_port_wr(hw, ENETC_PM0_PAUSE_QUANTA, init_quanta);
+ enetc_port_wr(hw, ENETC_PM1_PAUSE_QUANTA, init_quanta);
+ enetc_port_wr(hw, ENETC_PM0_PAUSE_THRESH, refresh_quanta);
+ enetc_port_wr(hw, ENETC_PM1_PAUSE_THRESH, refresh_quanta);
+ enetc_port_wr(hw, ENETC_PPAUONTR, pause_on_thresh);
+ enetc_port_wr(hw, ENETC_PPAUOFFTR, pause_off_thresh);
+
+ cmd_cfg = enetc_port_rd(hw, ENETC_PM0_CMD_CFG);
+
+ if (rx_pause)
+ cmd_cfg &= ~ENETC_PM0_PAUSE_IGN;
+ else
+ cmd_cfg |= ENETC_PM0_PAUSE_IGN;
+
+ enetc_port_wr(hw, ENETC_PM0_CMD_CFG, cmd_cfg);
+ enetc_port_wr(hw, ENETC_PM1_CMD_CFG, cmd_cfg);

- enetc_mac_enable(&pf->si->hw, true);
+ enetc_mac_enable(hw, true);
}

static void enetc_pl_mac_link_down(struct phylink_config *config,
--
2.25.1