[PATCH v2] net: dsa: qca8k: implement the port MTU callbacks

[Jonathan McDowell]

This switch has a single max frame size configuration register, so we
track the requested MTU for each port and apply the largest.

v2:
- Address review feedback from Vladimir Oltean

Signed-off-by: Jonathan McDowell <nood...@earth.li>
---
 drivers/net/dsa/qca8k.c | 31 +++++++++++++++++++++++++++++++
 drivers/net/dsa/qca8k.h |  3 +++
 2 files changed, 34 insertions(+)

diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
index 4acad5fa0c84..a5566de82853 100644
--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c
@@ -670,6 +670,11 @@ qca8k_setup(struct dsa_switch *ds)
                }
        }
 
+       /* Setup our port MTUs to match power on defaults */
+       for (i = 0; i < QCA8K_NUM_PORTS; i++)
+               priv->port_mtu[i] = ETH_FRAME_LEN + ETH_FCS_LEN;
+       qca8k_write(priv, QCA8K_MAX_FRAME_SIZE, ETH_FRAME_LEN + ETH_FCS_LEN);
+
        /* Flush the FDB table */
        qca8k_fdb_flush(priv);
 
@@ -1098,6 +1103,30 @@ qca8k_port_disable(struct dsa_switch *ds, int port)
        priv->port_sts[port].enabled = 0;
 }
 
+static int
+qca8k_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
+{
+       struct qca8k_priv *priv = ds->priv;
+       int i, mtu = 0;
+
+       priv->port_mtu[port] = new_mtu;
+
+       for (i = 0; i < QCA8K_NUM_PORTS; i++)
+               if (priv->port_mtu[port] > mtu)
+                       mtu = priv->port_mtu[port];
+
+       /* Include L2 header / FCS length */
+       qca8k_write(priv, QCA8K_MAX_FRAME_SIZE, mtu + ETH_HLEN + ETH_FCS_LEN);
+
+       return 0;
+}
+
+static int
+qca8k_port_max_mtu(struct dsa_switch *ds, int port)
+{
+       return QCA8K_MAX_MTU;
+}
+
 static int
 qca8k_port_fdb_insert(struct qca8k_priv *priv, const u8 *addr,
                      u16 port_mask, u16 vid)
@@ -1174,6 +1203,8 @@ static const struct dsa_switch_ops qca8k_switch_ops = {
        .set_mac_eee            = qca8k_set_mac_eee,
        .port_enable            = qca8k_port_enable,
        .port_disable           = qca8k_port_disable,
+       .port_change_mtu        = qca8k_port_change_mtu,
+       .port_max_mtu           = qca8k_port_max_mtu,
        .port_stp_state_set     = qca8k_port_stp_state_set,
        .port_bridge_join       = qca8k_port_bridge_join,
        .port_bridge_leave      = qca8k_port_bridge_leave,
diff --git a/drivers/net/dsa/qca8k.h b/drivers/net/dsa/qca8k.h
index 10ef2bca2cde..31439396401c 100644
--- a/drivers/net/dsa/qca8k.h
+++ b/drivers/net/dsa/qca8k.h
@@ -13,6 +13,7 @@
 #include <linux/gpio.h>
 
 #define QCA8K_NUM_PORTS                                        7
+#define QCA8K_MAX_MTU                                  9000
 
 #define PHY_ID_QCA8337                                 0x004dd036
 #define QCA8K_ID_QCA8337                               0x13
@@ -58,6 +59,7 @@
 #define   QCA8K_MDIO_MASTER_MAX_REG                    32
 #define QCA8K_GOL_MAC_ADDR0                            0x60
 #define QCA8K_GOL_MAC_ADDR1                            0x64
+#define QCA8K_MAX_FRAME_SIZE                           0x78
 #define QCA8K_REG_PORT_STATUS(_i)                      (0x07c + (_i) * 4)
 #define   QCA8K_PORT_STATUS_SPEED                      GENMASK(1, 0)
 #define   QCA8K_PORT_STATUS_SPEED_10                   0
@@ -189,6 +191,7 @@ struct qca8k_priv {
        struct device *dev;
        struct dsa_switch_ops ops;
        struct gpio_desc *reset_gpio;
+       unsigned int port_mtu[QCA8K_NUM_PORTS];
 };
 
 struct qca8k_mib_desc {
-- 
2.27.0