linux-kernel - Re: [PATCH net-next v4 1/2] net: dsa: microchip: ksz8: Make flow control, speed, and duplex on CPU port configurable

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Message-ID: <20230519232802.ae34asc4zgfmv3u4@skbuf>
Date:   Sat, 20 May 2023 02:28:02 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Eric Dumazet <edumazet@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Arun Ramadoss <arun.ramadoss@...rochip.com>,
        "Russell King (Oracle)" <linux@...linux.org.uk>,
        Simon Horman <simon.horman@...igine.com>,
        kernel@...gutronix.de, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net-next v4 1/2] net: dsa: microchip: ksz8: Make flow
 control, speed, and duplex on CPU port configurable

On Fri, May 19, 2023 at 02:46:59PM +0200, Oleksij Rempel wrote:
> diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchip/ksz8795.c
> index f56fca1b1a22..9eedccbf5b7c 100644
> --- a/drivers/net/dsa/microchip/ksz8795.c
> +++ b/drivers/net/dsa/microchip/ksz8795.c
> @@ -1371,6 +1371,57 @@ void ksz8_config_cpu_port(struct dsa_switch *ds)
> +/**
> + * ksz8_cpu_port_link_up - Configures the CPU port of the switch.
> + * @dev: The KSZ device instance.
> + * @speed: The desired link speed.
> + * @duplex: The desired duplex mode.
> + * @tx_pause: If true, enables transmit pause.
> + * @rx_pause: If true, enables receive pause.
> + *
> + * Description:
> + * The function configures flow control and speed settings for the CPU
> + * port of the switch based on the desired settings, current duplex mode, and
> + * speed.
> + */
> +static void ksz8_cpu_port_link_up(struct ksz_device *dev, int speed, int duplex,
> +				  bool tx_pause, bool rx_pause)
> +{
> +	u8 ctrl = 0;
> +
> +	/* SW_FLOW_CTRL, SW_HALF_DUPLEX, and SW_10_MBIT bits are bootstrappable
> +	 * at least on KSZ8873. They can have different values depending on your
> +	 * board setup.
> +	 */
> +	if (duplex) {
> +		if (tx_pause || rx_pause)
> +			ctrl |= SW_FLOW_CTRL;
> +	} else {
> +		ctrl |= SW_HALF_DUPLEX;
> +	}
> +
> +	/* This hardware only supports SPEED_10 and SPEED_100. For SPEED_10
> +	 * we need to set the SW_10_MBIT bit. Otherwise, we can leave it 0.
> +	 */
> +	if (speed == SPEED_10)
> +		ctrl |= SW_10_MBIT;
> +
> +	ksz_rmw8(dev, REG_SW_CTRL_4, SW_HALF_DUPLEX | SW_FLOW_CTRL |
> +		 SW_10_MBIT, ctrl);

REG_SW_CTRL_4 ... S_REPLACE_VID_CTRL ... dev->info->regs[P_XMII_CTRL_1] ...
at some point we will need one more consolidation effort here, since we
have at least 3 ways of reaching the same register.

> +}
> +
> +void ksz8_phylink_mac_link_up(struct ksz_device *dev, int port,
> +			      unsigned int mode, phy_interface_t interface,
> +			      struct phy_device *phydev, int speed, int duplex,
> +			      bool tx_pause, bool rx_pause)
> +{
> +	/* If the port is the CPU port, apply special handling. Only the CPU
> +	 * port is configured via global registers.
> +	 */
> +	if (dev->cpu_port == port)
> +		ksz8_cpu_port_link_up(dev, speed, duplex, tx_pause, rx_pause);
> +}
> +
>  static int ksz8_handle_global_errata(struct dsa_switch *ds)
>  {
>  	struct ksz_device *dev = ds->priv;
> @@ -1419,8 +1470,6 @@ int ksz8_setup(struct dsa_switch *ds)
>  	 */
>  	ds->vlan_filtering_is_global = true;
>  
> -	ksz_cfg(dev, S_REPLACE_VID_CTRL, SW_FLOW_CTRL, true);
> -
>  	/* Enable automatic fast aging when link changed detected. */
>  	ksz_cfg(dev, S_LINK_AGING_CTRL, SW_LINK_AUTO_AGING, true);
>  
> diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
> index a4428be5f483..6e19ad70c671 100644
> --- a/drivers/net/dsa/microchip/ksz_common.c
> +++ b/drivers/net/dsa/microchip/ksz_common.c
> @@ -210,6 +210,7 @@ static const struct ksz_dev_ops ksz8_dev_ops = {
>  	.mirror_add = ksz8_port_mirror_add,
>  	.mirror_del = ksz8_port_mirror_del,
>  	.get_caps = ksz8_get_caps,
> +	.phylink_mac_link_up = ksz8_phylink_mac_link_up,

Another future consolidation to consider: since all ksz_dev_ops now
provide .phylink_mac_link_up(), the "if" condition here is no longer
necessary:

static void ksz_phylink_mac_link_up(struct dsa_switch *ds, int port,
				    unsigned int mode,
				    phy_interface_t interface,
				    struct phy_device *phydev, int speed,
				    int duplex, bool tx_pause, bool rx_pause)
{
	struct ksz_device *dev = ds->priv;

	if (dev->dev_ops->phylink_mac_link_up)
		dev->dev_ops->phylink_mac_link_up(dev, port, mode, interface,
						  phydev, speed, duplex,
						  tx_pause, rx_pause);
}

which reminds me of the fact that I also had a patch to remove
dev->dev_ops->phylink_mac_config():
https://patchwork.kernel.org/project/netdevbpf/patch/20230316161250.3286055-5-vladimir.oltean@nxp.com/

I give up with that patch set now, since there's zero reviewer interest.
If you want and you think it's useful, you might want to adapt it for
KSZ8873.

>  	.config_cpu_port = ksz8_config_cpu_port,
>  	.enable_stp_addr = ksz8_enable_stp_addr,
>  	.reset = ksz8_reset_switch,
> -- 
> 2.39.2
> 

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