netdev - Re: [net-next PATCH RFC v6 11/16] net: dsa: qca8k: add tracking state of master port

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Message-ID: <20211215095146.6awhx44lamojipoo@skbuf>
Date:   Wed, 15 Dec 2021 11:51:46 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [net-next PATCH RFC v6 11/16] net: dsa: qca8k: add tracking
 state of master port

On Tue, Dec 14, 2021 at 11:44:04PM +0100, Ansuel Smith wrote:
> MDIO/MIB Ethernet require the master port and the tagger availabale to
> correctly work. Use the new api master_state_change to track when master
> is operational or not and set a bool in qca8k_priv.
> We cache the first cached master available and we check if other cpu
> port are operational when the cached one goes down.
> This cached master will later be used by mdio read/write and mib request to
> correctly use the working function.
> 
> qca8k implementation for MDIO/MIB Ethernet is bad. CPU port0 is the only
> one that answers with the ack packet or sends MIB Ethernet packets. For
> this reason the master_state_change ignore CPU port6 and checkes only
> CPU port0 if it's operational and enables this mode.

CPU port 0 may not always be wired, it depends on board design, right?
So the Ethernet management protocol may or may not be available to all users.

> 
> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
> diff --git a/drivers/net/dsa/qca8k.h b/drivers/net/dsa/qca8k.h
> index ab4a417b25a9..6edd6adc3063 100644
> --- a/drivers/net/dsa/qca8k.h
> +++ b/drivers/net/dsa/qca8k.h
> @@ -353,6 +353,7 @@ struct qca8k_priv {
>  	struct dsa_switch_ops ops;
>  	struct gpio_desc *reset_gpio;
>  	unsigned int port_mtu[QCA8K_NUM_PORTS];
> +	const struct net_device *master; /* Track if mdio/mib Ethernet is available */

Maybe "mgmt_master" would be a clearer naming scheme?

>  };
>  
>  struct qca8k_mib_desc {
> -- 
> 2.33.1
>