linux-kernel - Re: [PATCH v2] lan743x: add virtual PHY for PHY-less devices

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Message-ID: <3174210.ndmClRx9B8@metabook>
Date:   Sat, 23 Jan 2021 02:58:12 +0300
From:   Sergej Bauer <sbauer@...ckbox.su>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, f.fainelli@...il.com,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Bryan Whitehead <bryan.whitehead@...rochip.com>,
        UNGLinuxDriver@...rochip.com,
        Simon Horman <simon.horman@...ronome.com>,
        Mark Einon <mark.einon@...il.com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Arnd Bergmann <arnd@...db.de>,
        Masahiro Yamada <masahiroy@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] lan743x: add virtual PHY for PHY-less devices

On Saturday, January 23, 2021 2:23:25 AM MSK Andrew Lunn wrote:
> > > > @@ -1000,8 +1005,10 @@ static void lan743x_phy_close(struct
> > > > lan743x_adapter *adapter)>
> > > > 
> > > >  	struct net_device *netdev = adapter->netdev;
> > > >  	
> > > >  	phy_stop(netdev->phydev);
> > > > 
> > > > -	phy_disconnect(netdev->phydev);
> > > > -	netdev->phydev = NULL;
> > > > +	if (phy_is_pseudo_fixed_link(netdev->phydev))
> > > > +		lan743x_virtual_phy_disconnect(netdev->phydev);
> > > > +	else
> > > > +		phy_disconnect(netdev->phydev);
> > > 
> > > phy_disconnect() should work. You might want to call
> 
> There are drivers which call phy_disconnect() on a fixed_link. e.g.
> 
> https://elixir.bootlin.com/linux/v5.11-rc4/source/drivers/net/usb/lan78xx.c#
> L3555.
> 

> It could be your missing call to fixed_phy_unregister() is leaving
> behind bad state.
>
lan743x_virtual_phy_disconnect removes sysfs-links and calls 
fixed_phy_unregister()
and the reason was phydev in sysfs.

> > It was to make ethtool show full set of supported speeds and MII only in
> > supported ports (without TP and the no any ports in the bare card).
> 
> But fixed link does not support the full set of speed. It is fixed. It
> supports only one speed it is configured with.
That's why I "re-implemented the fixed PHY driver" as Florian said.
The goal of virtual phy was to make an illusion of real device working in
loopback mode. So I could use ethtool and ioctl's to switch speed of device.

> And by setting it
> wrongly, you are going to allow the user to do odd things, like use
> ethtool force the link speed to a speed which is not actually
> supported.
I have lan743x only and in loopback mode it allows to use speeds 
10/100/1000MBps
in full-duplex mode only. But the highest speed I have achived was something 
near
752Mbps...
And I can switch speed on the fly, without reloading the module.

May by I should limit the list of acceptable devices?

> 
>     Andrew