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

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Date:   Sun, 11 Aug 2019 18:14:45 +0200
From:   Marek Behun <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 Sun, 11 Aug 2019 17:31:53 +0200
Andrew Lunn <andrew@...n.ch> wrote:

> On Sun, Aug 11, 2019 at 05:08:11PM +0200, Marek Behún wrote:
> > The mv88e6xxx_port_setup_mac looks if one of the {link, speed, duplex}
> > parameters is being changed from the current setting, and if not, does
> > not do anything. This test is wrong in some situations: this method also
> > has the mode argument, which can also be changed.
> > 
> > For example on Turris Omnia, the mode is PHY_INTERFACE_MODE_RGMII_ID,
> > which has to be set byt the ->port_set_rgmii_delay method. The test does
> > not look if mode is being changed (in fact there is currently no method
> > to determine port mode as phy_interface_t type).
> > 
> > The simplest solution seems to be to drop this test altogether and
> > simply do the setup when requested.  
> 
> Hi Marek
> 
> Unfortunately, that code is there for a reason. phylink can call the
> ->mac_config() method once per second. It is documented that  
> mac_config() should only reconfigure what, if anything, has changed.
> And mv88e6xxx_port_setup_mac() needs to disable the port in order to
> change anything. So the change you propose here, under some
> conditions, will cause the port to be disabled/enables once per
> second.
> 
> We need to fix this by expanding the test, not removing it.  My
> current _guess_ would be, we need to add a ops->port_get_rgmii_delay()
> so we can see if that is what needs configuring.
> 
>    Andrew

Hi Andrew,
what if we added a phy_mode member to struct mv88e6xxx_port, and either
set it to PHY_INTERFACE_MODE_NA in mv88e6xxx_setup, or implemented
methods for converting the switch register values to
PHY_INTERFACE_MODE_* values.
This way we could just add port.mode == mode check to port_setup_mac
method.
I am willing to implement this if you think this could work.

Marek