Re: [PATCH net-next v4 1/1] net: dsa: microchip: ksz9477: implement MTU configuration

[Vladimir Oltean <olteanv@gmail.com>]

On Tue, Mar 08, 2022 at 02:36:57PM +0100, Oleksij Rempel wrote:
> This chips supports two ways to configure max MTU size:
> - by setting SW_LEGAL_PACKET_DISABLE bit: if this bit is 0 allowed packed size
>   will be between 64 and bytes 1518. If this bit is 1, it will accept
>   packets up to 2000 bytes.
> - by setting SW_JUMBO_PACKET bit. If this bit is set, the chip will
>   ignore SW_LEGAL_PACKET_DISABLE value and use REG_SW_MTU__2 register to
>   configure MTU size.
> 
> Current driver has disabled SW_JUMBO_PACKET bit and activates
> SW_LEGAL_PACKET_DISABLE. So the switch will pass all packets up to 2000 without
> any way to configure it.
> 
> By providing port_change_mtu we are switch to SW_JUMBO_PACKET way and will
> be able to configure MTU up to ~9000.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---

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

> changes v4:
> - fix MTU for VLAN
> changes v3:
> - do more testing and fix mtu configuration
> changes v2:
> - rename max_mtu to max_frame and new_mtu to frame_size
> - use max() instead of if(>)
> ---
>  drivers/net/dsa/microchip/ksz9477.c     | 36 +++++++++++++++++++++++--
>  drivers/net/dsa/microchip/ksz9477_reg.h |  3 +++
>  drivers/net/dsa/microchip/ksz_common.h  |  1 +
>  3 files changed, 38 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/dsa/microchip/ksz9477.c b/drivers/net/dsa/microchip/ksz9477.c
> index 94ad6d9504f4..f9e4d5a98f8c 100644
> --- a/drivers/net/dsa/microchip/ksz9477.c
> +++ b/drivers/net/dsa/microchip/ksz9477.c
> @@ -11,6 +11,7 @@
>  #include <linux/platform_data/microchip-ksz.h>
>  #include <linux/phy.h>
>  #include <linux/if_bridge.h>
> +#include <linux/if_vlan.h>
>  #include <net/dsa.h>
>  #include <net/switchdev.h>
>  
> @@ -182,6 +183,29 @@ static void ksz9477_port_cfg32(struct ksz_device *dev, int port, int offset,
>  			   bits, set ? bits : 0);
>  }
>  
> +static int ksz9477_change_mtu(struct dsa_switch *ds, int port, int mtu)
> +{
> +	struct ksz_device *dev = ds->priv;
> +	u16 frame_size, max_frame = 0;
> +	int i;
> +
> +	frame_size = mtu + ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN;

Nitpick: ETH_HLEN + VLAN_HLEN == VLAN_ETH_HLEN.

> +
> +	/* Cache the per-port MTU setting */
> +	dev->ports[port].max_frame = frame_size;
> +
> +	for (i = 0; i < dev->port_cnt; i++)
> +		max_frame = max(max_frame, dev->ports[i].max_frame);
> +
> +	return regmap_update_bits(dev->regmap[1], REG_SW_MTU__2,
> +				  REG_SW_MTU_MASK, max_frame);
> +}
> +
> +static int ksz9477_max_mtu(struct dsa_switch *ds, int port)
> +{
> +	return KSZ9477_MAX_FRAME_SIZE - ETH_HLEN - VLAN_HLEN - ETH_FCS_LEN;
> +}
> +
>  static int ksz9477_wait_vlan_ctrl_ready(struct ksz_device *dev)
>  {
>  	unsigned int val;
> @@ -1416,8 +1440,14 @@ static int ksz9477_setup(struct dsa_switch *ds)
>  	/* Do not work correctly with tail tagging. */
>  	ksz_cfg(dev, REG_SW_MAC_CTRL_0, SW_CHECK_LENGTH, false);
>  
> -	/* accept packet up to 2000bytes */
> -	ksz_cfg(dev, REG_SW_MAC_CTRL_1, SW_LEGAL_PACKET_DISABLE, true);
> +	/* Enable REG_SW_MTU__2 reg by setting SW_JUMBO_PACKET */
> +	ksz_cfg(dev, REG_SW_MAC_CTRL_1, SW_JUMBO_PACKET, true);
> +
> +	/* Now we can configure default MTU value */
> +	ret = regmap_update_bits(dev->regmap[1], REG_SW_MTU__2, REG_SW_MTU_MASK,
> +				 VLAN_ETH_FRAME_LEN + ETH_FCS_LEN);
> +	if (ret)
> +		return ret;
>  
>  	ksz9477_config_cpu_port(ds);
>  
> @@ -1464,6 +1494,8 @@ static const struct dsa_switch_ops ksz9477_switch_ops = {
>  	.port_mirror_add	= ksz9477_port_mirror_add,
>  	.port_mirror_del	= ksz9477_port_mirror_del,
>  	.get_stats64		= ksz9477_get_stats64,
> +	.port_change_mtu	= ksz9477_change_mtu,
> +	.port_max_mtu		= ksz9477_max_mtu,
>  };
>  
>  static u32 ksz9477_get_port_addr(int port, int offset)
> diff --git a/drivers/net/dsa/microchip/ksz9477_reg.h b/drivers/net/dsa/microchip/ksz9477_reg.h
> index 16939f29faa5..0bd58467181f 100644
> --- a/drivers/net/dsa/microchip/ksz9477_reg.h
> +++ b/drivers/net/dsa/microchip/ksz9477_reg.h
> @@ -176,6 +176,7 @@
>  #define REG_SW_MAC_ADDR_5		0x0307
>  
>  #define REG_SW_MTU__2			0x0308
> +#define REG_SW_MTU_MASK			GENMASK(13, 0)
>  
>  #define REG_SW_ISP_TPID__2		0x030A
>  
> @@ -1662,4 +1663,6 @@
>  /* 148,800 frames * 67 ms / 100 */
>  #define BROADCAST_STORM_VALUE		9969
>  
> +#define KSZ9477_MAX_FRAME_SIZE		9000
> +
>  #endif /* KSZ9477_REGS_H */
> diff --git a/drivers/net/dsa/microchip/ksz_common.h b/drivers/net/dsa/microchip/ksz_common.h
> index 4ff0a159ce3c..fa39ee73cbd2 100644
> --- a/drivers/net/dsa/microchip/ksz_common.h
> +++ b/drivers/net/dsa/microchip/ksz_common.h
> @@ -41,6 +41,7 @@ struct ksz_port {
>  
>  	struct ksz_port_mib mib;
>  	phy_interface_t interface;
> +	u16 max_frame;
>  };
>  
>  struct ksz_device {
> -- 
> 2.30.2
>