netdev - Re: [PATCH net-next 1/2] net: dsa: mv88e6xxx: fix RGMII-ID port setup

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Message-ID: <20190813175124.06d8cdf5@dellmb.labs.office.nic.cz>
Date:   Tue, 13 Aug 2019 17:51:24 +0200
From:   Marek Behún <marek.behun@....cz>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>,
        Sebastian Reichel <sebastian.reichel@...labora.co.uk>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next 1/2] net: dsa: mv88e6xxx: fix RGMII-ID port
 setup

On Tue, 13 Aug 2019 17:44:16 +0200
Marek Behún <marek.behun@....cz> wrote:

> Hi Andrew,
> 
> > We should read the switch registers. I think you can set the
> > defaults using strapping pins. And in general, the driver always
> > reads state from the hardware rather than caching it.  
> 
> hmm. The cmode is cached for each port, though. For example
> mv88e6390x_port_set_cmode compares the new requested value with the
> cached one and doesn't do anything if they are equal.
> 
> If mv88e6xxx_port_setup_mac can be called once per second by phylink
> as you say, do we really want to read the value via MDIO every time?
> We already have cmode cached (read from registers at mv88e6xxx_setup,
> and then changed when cmode change is requested). From cmode we can
> already differentiate mode in the terms of phy_interface_t, unless it
> is RGMII, in which case we would have to read RX/TX timing.
> 
> Marek

/o\ OK. I see now that mv88e6xxx_port_setup_mac already calls
->port_link_state(), which fills in a struct phylink_link_state, and
already does MDIO communication. Sorry :)
I will try to send a patch which adds the filling of the ->interface
member of the struct phylink_link_state in ->port_link_state() method.

Marek