netdev - Re: [PATCH net v2] net: phy: phy_ethtool_ksettings_set: Don't discard phy_start

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Message-ID: <YYlnCx+S34B1b5Xy@shell.armlinux.org.uk>
Date:   Mon, 8 Nov 2021 18:06:03 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Bastian Germann <bage@...utronix.de>,
        Benedikt Spranger <b.spranger@...utronix.de>,
        davem@...emloft.net, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH net v2] net: phy: phy_ethtool_ksettings_set: Don't
 discard phy_start_aneg's return

On Mon, Nov 08, 2021 at 07:01:23PM +0100, Heiner Kallweit wrote:
> On 08.11.2021 18:57, Andrew Lunn wrote:
> >> It is BCM53125. Currently, you can set "mdix auto|off|on" which does
> >> not take any effect.  The chip will do what is its default depending
> >> on copper autonegotiation.
> >>
> >> I am adding support for setting "mdix auto|off". I want the thing to error on "mdix on".
> >> Where would I add that check?
> > 
> > /* MDI or MDI-X status/control - if MDI/MDI_X/AUTO is set then
> >  * the driver is required to renegotiate link
> >  */
> > #define ETH_TP_MDI_INVALID	0x00 /* status: unknown; control: unsupported */
> > #define ETH_TP_MDI		0x01 /* status: MDI;     control: force MDI */
> > #define ETH_TP_MDI_X		0x02 /* status: MDI-X;   control: force MDI-X */
> > #define ETH_TP_MDI_AUTO		0x03 /*                  control: auto-select */
> > 
> > So there are three valid settings. And you are saying you only want to
> > implement two of them? If the hardware can do all three, you should
> > implement all three.
> > 
> 
> If we would like to support PHY's that don't support all MDI modes then
> supposedly this would require to add ETHTOOL_LINK_MODE bits for the
> MDI modes. Then we could use the generic mechanism to check the bits in
> the "supported" bitmap.

We'll have to add more stuff to phylink to avoid MACs masking these
bits... ETHTOOL_LINK_MODE seems to be becoming a disorganised dumping
ground for random stuff. :(

Also, what would these bits in the advertising bitmap mean?

Finally, how do we handle the lack of these bits for existing PHYs
that already implement MDI modes?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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