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Date:   Mon, 20 Jul 2020 15:50:57 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     Russell King <rmk+kernel@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>
CC:     Vladimir Oltean <vladimir.oltean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandru Marginean <alexandru.marginean@....com>,
        "michael@...le.cc" <michael@...le.cc>,
        "olteanv@...il.com" <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH RFC net-next 12/13] net: phylink: add struct phylink_pcs

On 6/30/20 5:29 PM, Russell King wrote:
> Add a way for MAC PCS to have private data while keeping independence
> from struct phylink_config, which is used for the MAC itself. We need
> this independence as we will have stand-alone code for PCS that is
> independent of the MAC.  Introduce struct phylink_pcs, which is
> designed to be embedded in a driver private data structure.
> 
> This structure does not include a mdio_device as there are PCS
> implementations such as the Marvell DSA and network drivers where this
> is not necessary.
> 
> Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>

Reviewed-by: Ioana Ciornei <ioana.ciornei@....com>

I integrated and used the phylink_pcs structure into the Lynx PCS just 
to see how everything fits. Pasting below the main parts so that we can 
catch early any possible different opinions on how to integrate this:

The basic Lynx structure looks like below and the main idea is just to 
encapsulate the phylink_pcs structure and the mdio device (which in some 
other cases might not be needed).

struct lynx_pcs {
        struct phylink_pcs pcs;
        struct mdio_device *mdio;
        phy_interface_t interface;
};

The lynx_pcs structure is requested by the MAC driver with:

struct lynx_pcs *lynx_pcs_create(struct mdio_device *mdio)
{
(...)
        lynx_pcs->mdio = mdio;
        lynx_pcs->pcs.ops = &lynx_pcs_phylink_ops;
        lynx_pcs->pcs.poll = true;

        return lynx_pcs;
}

And then passed to phylink with something like:

phylink_set_pcs(pl, &lynx_pcs->pcs);


For DSA it's a bit less straightforward because the .setup() callback 
from the dsa_switch_ops is run before any phylink structure has been 
created internally. For this, a new DSA helper can be created that just 
stores the phylink_pcs structure per port:

void dsa_port_phylink_set_pcs(struct dsa_switch *ds, int port,
                              struct phylink_pcs *pcs)
{
        struct dsa_port *dp = dsa_to_port(ds, port);

        dp->pcs = pcs;                                         but I do
}

and at the appropriate time, from dsa_slave_setup, it can really install 
the phylink_pcs with phylink_set_pcs.
The other option would be to add a new dsa_switch ops that requests the 
phylink_pcs for a specific port - something like phylink_get_pcs.

Ioana


> ---
>   drivers/net/phy/phylink.c | 25 ++++++++++++++++------
>   include/linux/phylink.h   | 45 ++++++++++++++++++++++++++-------------
>   2 files changed, 48 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> index a31a00fb4974..fbc8591b474b 100644
> --- a/drivers/net/phy/phylink.c
> +++ b/drivers/net/phy/phylink.c
> @@ -43,6 +43,7 @@ struct phylink {
>   	const struct phylink_mac_ops *mac_ops;
>   	const struct phylink_pcs_ops *pcs_ops;
>   	struct phylink_config *config;
> +	struct phylink_pcs *pcs;
>   	struct device *dev;
>   	unsigned int old_link_state:1;
>   
> @@ -427,7 +428,7 @@ static void phylink_mac_pcs_an_restart(struct phylink *pl)
>   	    phy_interface_mode_is_8023z(pl->link_config.interface) &&
>   	    phylink_autoneg_inband(pl->cur_link_an_mode)) {
>   		if (pl->pcs_ops)
> -			pl->pcs_ops->pcs_an_restart(pl->config);
> +			pl->pcs_ops->pcs_an_restart(pl->pcs);
>   		else
>   			pl->mac_ops->mac_an_restart(pl->config);
>   	}
> @@ -453,7 +454,7 @@ static void phylink_change_interface(struct phylink *pl, bool restart,
>   	phylink_mac_config(pl, state);
>   
>   	if (pl->pcs_ops) {
> -		err = pl->pcs_ops->pcs_config(pl->config, pl->cur_link_an_mode,
> +		err = pl->pcs_ops->pcs_config(pl->pcs, pl->cur_link_an_mode,
>   					      state->interface,
>   					      state->advertising,
>   					      !!(pl->link_config.pause &
> @@ -533,7 +534,7 @@ static void phylink_mac_pcs_get_state(struct phylink *pl,
>   	state->link = 1;
>   
>   	if (pl->pcs_ops)
> -		pl->pcs_ops->pcs_get_state(pl->config, state);
> +		pl->pcs_ops->pcs_get_state(pl->pcs, state);
>   	else
>   		pl->mac_ops->mac_pcs_get_state(pl->config, state);
>   }
> @@ -604,7 +605,7 @@ static void phylink_link_up(struct phylink *pl,
>   	pl->cur_interface = link_state.interface;
>   
>   	if (pl->pcs_ops && pl->pcs_ops->pcs_link_up)
> -		pl->pcs_ops->pcs_link_up(pl->config, pl->cur_link_an_mode,
> +		pl->pcs_ops->pcs_link_up(pl->pcs, pl->cur_link_an_mode,
>   					 pl->cur_interface,
>   					 link_state.speed, link_state.duplex);
>   
> @@ -863,11 +864,19 @@ struct phylink *phylink_create(struct phylink_config *config,
>   }
>   EXPORT_SYMBOL_GPL(phylink_create);
>   
> -void phylink_add_pcs(struct phylink *pl, const struct phylink_pcs_ops *ops)
> +/**
> + * phylink_set_pcs() - set the current PCS for phylink to use
> + * @pl: a pointer to a &struct phylink returned from phylink_create()
> + * @pcs: a pointer to the &struct phylink_pcs
> + *
> + * Bind the MAC PCS to phylink.
> + */
> +void phylink_set_pcs(struct phylink *pl, struct phylink_pcs *pcs)
>   {
> -	pl->pcs_ops = ops;
> +	pl->pcs = pcs;
> +	pl->pcs_ops = pcs->ops;
>   }
> -EXPORT_SYMBOL_GPL(phylink_add_pcs);
> +EXPORT_SYMBOL_GPL(phylink_set_pcs);
>   
>   /**
>    * phylink_destroy() - cleanup and destroy the phylink instance
> @@ -1212,6 +1221,8 @@ void phylink_start(struct phylink *pl)
>   		break;
>   	case MLO_AN_INBAND:
>   		poll |= pl->config->pcs_poll;
> +		if (pl->pcs)
> +			poll |= pl->pcs->poll;
>   		break;
>   	}
>   	if (poll)
> diff --git a/include/linux/phylink.h b/include/linux/phylink.h
> index 2f1315f32113..057f78263a46 100644
> --- a/include/linux/phylink.h
> +++ b/include/linux/phylink.h
> @@ -321,6 +321,21 @@ void mac_link_up(struct phylink_config *config, struct phy_device *phy,
>   		 int speed, int duplex, bool tx_pause, bool rx_pause);
>   #endif
>   
> +struct phylink_pcs_ops;
> +
> +/**
> + * struct phylink_pcs - PHYLINK PCS instance
> + * @ops: a pointer to the &struct phylink_pcs_ops structure
> + * @poll: poll the PCS for link changes
> + *
> + * This structure is designed to be embedded within the PCS private data,
> + * and will be passed between phylink and the PCS.
> + */
> +struct phylink_pcs {
> +	const struct phylink_pcs_ops *ops;
> +	bool poll;
> +};
> +
>   /**
>    * struct phylink_pcs_ops - MAC PCS operations structure.
>    * @pcs_get_state: read the current MAC PCS link state from the hardware.
> @@ -330,21 +345,21 @@ void mac_link_up(struct phylink_config *config, struct phy_device *phy,
>    *               (where necessary).
>    */
>   struct phylink_pcs_ops {
> -	void (*pcs_get_state)(struct phylink_config *config,
> +	void (*pcs_get_state)(struct phylink_pcs *pcs,
>   			      struct phylink_link_state *state);
> -	int (*pcs_config)(struct phylink_config *config, unsigned int mode,
> +	int (*pcs_config)(struct phylink_pcs *pcs, unsigned int mode,
>   			  phy_interface_t interface,
>   			  const unsigned long *advertising,
>   			  bool permit_pause_to_mac);
> -	void (*pcs_an_restart)(struct phylink_config *config);
> -	void (*pcs_link_up)(struct phylink_config *config, unsigned int mode,
> +	void (*pcs_an_restart)(struct phylink_pcs *pcs);
> +	void (*pcs_link_up)(struct phylink_pcs *pcs, unsigned int mode,
>   			    phy_interface_t interface, int speed, int duplex);
>   };
>   
>   #if 0 /* For kernel-doc purposes only. */
>   /**
>    * pcs_get_state() - Read the current inband link state from the hardware
> - * @config: a pointer to a &struct phylink_config.
> + * @pcs: a pointer to a &struct phylink_pcs.
>    * @state: a pointer to a &struct phylink_link_state.
>    *
>    * Read the current inband link state from the MAC PCS, reporting the
> @@ -357,12 +372,12 @@ struct phylink_pcs_ops {
>    * When present, this overrides mac_pcs_get_state() in &struct
>    * phylink_mac_ops.
>    */
> -void pcs_get_state(struct phylink_config *config,
> +void pcs_get_state(struct phylink_pcs *pcs,
>   		   struct phylink_link_state *state);
>   
>   /**
>    * pcs_config() - Configure the PCS mode and advertisement
> - * @config: a pointer to a &struct phylink_config.
> + * @pcs: a pointer to a &struct phylink_pcs.
>    * @mode: one of %MLO_AN_FIXED, %MLO_AN_PHY, %MLO_AN_INBAND.
>    * @interface: interface mode to be used
>    * @advertising: adertisement ethtool link mode mask
> @@ -382,21 +397,21 @@ void pcs_get_state(struct phylink_config *config,
>    *
>    * For most 10GBASE-R, there is no advertisement.
>    */
> -int (*pcs_config)(struct phylink_config *config, unsigned int mode,
> -		  phy_interface_t interface, const unsigned long *advertising);
> +int pcs_config(struct phylink_pcs *pcs, unsigned int mode,
> +	       phy_interface_t interface, const unsigned long *advertising);
>   
>   /**
>    * pcs_an_restart() - restart 802.3z BaseX autonegotiation
> - * @config: a pointer to a &struct phylink_config.
> + * @pcs: a pointer to a &struct phylink_pcs.
>    *
>    * When PCS ops are present, this overrides mac_an_restart() in &struct
>    * phylink_mac_ops.
>    */
> -void (*pcs_an_restart)(struct phylink_config *config);
> +void pcs_an_restart(struct phylink_pcs *pcs);
>   
>   /**
>    * pcs_link_up() - program the PCS for the resolved link configuration
> - * @config: a pointer to a &struct phylink_config.
> + * @pcs: a pointer to a &struct phylink_pcs.
>    * @mode: link autonegotiation mode
>    * @interface: link &typedef phy_interface_t mode
>    * @speed: link speed
> @@ -407,14 +422,14 @@ void (*pcs_an_restart)(struct phylink_config *config);
>    * mode without in-band AN needs to be manually configured for the link
>    * and duplex setting. Otherwise, this should be a no-op.
>    */
> -void (*pcs_link_up)(struct phylink_config *config, unsigned int mode,
> -		    phy_interface_t interface, int speed, int duplex);
> +void pcs_link_up(struct phylink_pcs *pcs, unsigned int mode,
> +		 phy_interface_t interface, int speed, int duplex);
>   #endif
>   
>   struct phylink *phylink_create(struct phylink_config *, struct fwnode_handle *,
>   			       phy_interface_t iface,
>   			       const struct phylink_mac_ops *mac_ops);
> -void phylink_add_pcs(struct phylink *, const struct phylink_pcs_ops *ops);
> +void phylink_set_pcs(struct phylink *, struct phylink_pcs *pcs);
>   void phylink_destroy(struct phylink *);
>   
>   int phylink_connect_phy(struct phylink *, struct phy_device *);
> 

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