linux-kernel - Re: [net-next PATCH v2 2/2] net: airoha: add phylink support for GDM1

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Message-ID: <aP00w4CQdeX9GIJA@shell.armlinux.org.uk>
Date: Sat, 25 Oct 2025 21:36:19 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Lorenzo Bianconi <lorenzo@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH v2 2/2] net: airoha: add phylink support for GDM1

On Thu, Oct 23, 2025 at 04:58:49PM +0200, Christian Marangi wrote:
> In preparation for support of GDM2+ port, fill in phylink OPs for GDM1
> that is an INTERNAL port for the Embedded Switch.
> 
> Add all the phylink start/stop and fill in the MAC capabilities and the
> internal interface as the supported interface.
> 
> Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
> ---
>  drivers/net/ethernet/airoha/Kconfig      |  1 +
>  drivers/net/ethernet/airoha/airoha_eth.c | 77 +++++++++++++++++++++++-
>  drivers/net/ethernet/airoha/airoha_eth.h |  3 +
>  3 files changed, 80 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/airoha/Kconfig b/drivers/net/ethernet/airoha/Kconfig
> index ad3ce501e7a5..3c74438bc8a0 100644
> --- a/drivers/net/ethernet/airoha/Kconfig
> +++ b/drivers/net/ethernet/airoha/Kconfig
> @@ -2,6 +2,7 @@
>  config NET_VENDOR_AIROHA
>  	bool "Airoha devices"
>  	depends on ARCH_AIROHA || COMPILE_TEST
> +	select PHYLIB

This looks wrong if you're using phylink.

>  	help
>  	  If you have a Airoha SoC with ethernet, say Y.
>  
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> index ce6d13b10e27..deba909104bb 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.c
> +++ b/drivers/net/ethernet/airoha/airoha_eth.c
> @@ -1613,6 +1613,8 @@ static int airoha_dev_open(struct net_device *dev)
>  	struct airoha_gdm_port *port = netdev_priv(dev);
>  	struct airoha_qdma *qdma = port->qdma;
>  
> +	phylink_start(port->phylink);
> +
>  	netif_tx_start_all_queues(dev);
>  	err = airoha_set_vip_for_gdm_port(port, true);
>  	if (err)

phylink_start() _can_ bring the carrier up immediately. Is the netdev
ready to start operating at the point phylink_start() has been called?
This error handling suggests the answer is "no", and the lack of
phylink_stop() in the error path is also a red flag.

> @@ -1665,6 +1667,8 @@ static int airoha_dev_stop(struct net_device *dev)
>  		}
>  	}
>  
> +	phylink_stop(port->phylink);
> +
>  	return 0;
>  }
>  
> @@ -2813,6 +2817,18 @@ static const struct ethtool_ops airoha_ethtool_ops = {
>  	.get_link		= ethtool_op_get_link,
>  };
>  
> +static struct phylink_pcs *airoha_phylink_mac_select_pcs(struct phylink_config *config,
> +			phy_interface_t interface)

I'd write this as:

static struct phylink_pcs *
airoha_phylink_mac_select_pcs(struct phylink_config *config,
			      phy_interface_t interface)

but:

> +{
> +	return NULL;
> +}

Not sure what the point of this is, as this will be the effect if
this function is not provided.

> +
> +static void airoha_mac_config(struct phylink_config *config,
> +			      unsigned int mode,
> +			      const struct phylink_link_state *state)
> +{
> +}
> +
>  static int airoha_metadata_dst_alloc(struct airoha_gdm_port *port)
>  {
>  	int i;
> @@ -2857,6 +2873,57 @@ bool airoha_is_valid_gdm_port(struct airoha_eth *eth,
>  	return false;
>  }
>  
> +static void airoha_mac_link_up(struct phylink_config *config,
> +			       struct phy_device *phy, unsigned int mode,
> +			       phy_interface_t interface, int speed,
> +			       int duplex, bool tx_pause, bool rx_pause)
> +{
> +}
> +
> +static void airoha_mac_link_down(struct phylink_config *config,
> +				 unsigned int mode, phy_interface_t interface)
> +{
> +}
> +
> +static const struct phylink_mac_ops airoha_phylink_ops = {
> +	.mac_select_pcs = airoha_phylink_mac_select_pcs,
> +	.mac_config = airoha_mac_config,
> +	.mac_link_up = airoha_mac_link_up,
> +	.mac_link_down = airoha_mac_link_down,
> +};

All the called methods are entirely empty, meaning that anything that
phylink reports may not reflect what is going on with the device.

Is there a plan to implement these methods?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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