Subject: Re: [PATCH net-next v5 1/3] net: dsa: microchip: ksz8: Make flow control, speed, and duplex on CPU port configurable

From: "Russell King (Oracle)" <[email-masked]>
Date: Wed, 22 Nov 2023 09:38:09 +0000

On Wed, Nov 22, 2023 at 10:25:43AM +0100, Oleksij Rempel wrote:
> Allow flow control, speed, and duplex settings on the CPU port to be
> configurable. Previously, the speed and duplex relied on default switch
> values, which limited flexibility. Additionally, flow control was
> hardcoded and only functional in duplex mode. This update enhances the
> configurability of these parameters.
> 
> Signed-off-by: Oleksij Rempel <[email-masked]>
> Reviewed-by: Simon Horman <[email-masked]>
> Reviewed-by: Vladimir Oltean <[email-masked]>
> ---
>  drivers/net/dsa/microchip/ksz8.h       |  4 ++
>  drivers/net/dsa/microchip/ksz8795.c    | 54 +++++++++++++++++++++++++-
>  drivers/net/dsa/microchip/ksz_common.c |  1 +
>  3 files changed, 57 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/dsa/microchip/ksz8.h b/drivers/net/dsa/microchip/ksz8.h
> index ef653bbfde75..571c26ce71e4 100644
> --- a/drivers/net/dsa/microchip/ksz8.h
> +++ b/drivers/net/dsa/microchip/ksz8.h
> @@ -54,5 +54,9 @@ int ksz8_reset_switch(struct ksz_device *dev);
>  int ksz8_switch_init(struct ksz_device *dev);
>  void ksz8_switch_exit(struct ksz_device *dev);
>  int ksz8_change_mtu(struct ksz_device *dev, int port, int mtu);
> +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);
>  
>  #endif
> diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchip/ksz8795.c
> index 8deb217638d3..3504e7238eba 100644
> --- a/drivers/net/dsa/microchip/ksz8795.c
> +++ b/drivers/net/dsa/microchip/ksz8795.c
> @@ -1528,6 +1528,58 @@ 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)
> +{
> +	const u16 *regs = dev->info->regs;
> +	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;

Please don't make this dependent on duplex, and allow phylink to enforce
that. For example, phylink_resolve_an_pause() will only enable tx/rx
pause if in full duplex mode.

> +	} 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, regs[S_BROADCAST_CTRL], SW_HALF_DUPLEX | SW_FLOW_CTRL |
> +		 SW_10_MBIT, ctrl);

So this is using SW_FLOW_CTRL with the S_BROADCAST_CTRL register...

> @@ -1576,8 +1628,6 @@ int ksz8_setup(struct dsa_switch *ds)
>  	 */
>  	ds->vlan_filtering_is_global = true;
>  
> -	ksz_cfg(dev, S_REPLACE_VID_CTRL, SW_FLOW_CTRL, true);

But previously it was being used with the S_REPLACE_VID_CTRL register.
Doesn't make sense to me.

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