linux-kernel - Re: [PATCH net-next v3] net: phy: broadcom: add 1000Base-X support for BCM54616S

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Date:   Sun, 4 Aug 2019 22:22:01 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Tao Ren <taoren@...com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Arun Parameswaran <arun.parameswaran@...adcom.com>,
        Justin Chen <justinpopo6@...il.com>,
        netdev <netdev@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>
Subject: Re: [PATCH net-next v3] net: phy: broadcom: add 1000Base-X support
 for BCM54616S

On Sun, 4 Aug 2019 at 19:07, Heiner Kallweit <hkallweit1@...il.com> wrote:
>
> On 04.08.2019 17:59, Vladimir Oltean wrote:
> > On Sun, 4 Aug 2019 at 17:52, Andrew Lunn <andrew@...n.ch> wrote:
> >>
> >>>> The patchset looks better now. But is it ok, I wonder, to keep
> >>>> PHY_BCM_FLAGS_MODE_1000BX in phydev->dev_flags, considering that
> >>>> phy_attach_direct is overwriting it?
> >>>
> >>
> >>> I checked ftgmac100 driver (used on my machine) and it calls
> >>> phy_connect_direct which passes phydev->dev_flags when calling
> >>> phy_attach_direct: that explains why the flag is not cleared in my
> >>> case.
> >>
> >> Yes, that is the way it is intended to be used. The MAC driver can
> >> pass flags to the PHY. It is a fragile API, since the MAC needs to
> >> know what PHY is being used, since the flags are driver specific.
> >>
> >> One option would be to modify the assignment in phy_attach_direct() to
> >> OR in the flags passed to it with flags which are already in
> >> phydev->dev_flags.
> >>
> >>         Andrew
> >
> > Even if that were the case (patching phy_attach_direct to apply a
> > logical-or to dev_flags), it sounds fishy to me that the genphy code
> > is unable to determine that this PHY is running in 1000Base-X mode.
> >
> > In my opinion it all boils down to this warning:
> >
> > "PHY advertising (0,00000200,000062c0) more modes than genphy
> > supports, some modes not advertised".
> >
> The genphy code deals with Clause 22 + Gigabit BaseT only.
> Question is whether you want aneg at all in 1000Base-X mode and
> what you want the config_aneg callback to do.
> There may be some inspiration in the Marvel PHY drivers.
>

AN for 1000Base-X still gives you duplex and pause frame settings. I
thought the base page format for exchanging that info is standardized
in clause 37.
Does genphy cover only copper media by design, or is it desirable to
augment genphy_read_status?

> > You see, the 0x200 in the above advertising mask corresponds exactly
> > to this definition from ethtool.h:
> >     ETHTOOL_LINK_MODE_1000baseX_Full_BIT    = 41,
> >
> > But it gets truncated and hence lost.
> >
> > Regards,
> > -Vladimir
> >
> Heiner