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

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 <noodles@earth.li>
---
 drivers/net/dsa/qca8k.c | 31 +++++++++++++++++++++++++++++++
 drivers/net/dsa/qca8k.h |  3 +++
 2 files changed, 34 insertions(+)

On Sat, Jul 18, 2020 at 05:32:14PM +0100, Jonathan McDowell wrote:
> 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 <noodles@earth.li>
> ---

I think there's still an open question on whether the slave_dev->mtu of
all other ports should be updated to reflect the new, potentially larger
value. But we could always update drivers after the fact, if that ever
becomes required.

Acked-by: Vladimir Oltean <olteanv@gmail.com>

>  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
>

From: Jonathan McDowell <noodles@earth.li>
Date: Sat, 18 Jul 2020 17:32:14 +0100

> 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 <noodles@earth.li>

Applied to net-next, thanks.