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Date:   Tue, 3 Mar 2020 14:59:36 +0100
From:   Andrew Lunn <andrew@lunn.ch>
To:     Oleksij Rempel <o.rempel@pengutronix.de>
Cc:     Florian Fainelli <f.fainelli@gmail.com>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        linux-kernel@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        Marek Vasut <marex@denx.de>, David Jander <david@protonic.nl>,
        Quentin Schulz <quentin.schulz@bootlin.com>
Subject: Re: [PATCH v1] net: phy: tja11xx: add TJA1102 support
Message-ID: <20200303135936.GG31977@lunn.ch>
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Hi Oleksij

> TJA1102 is an dual T1 PHY chip. Both PHYs are separately addressable.
> PHY 0 can be identified by PHY ID. PHY 1 has no PHY ID and can be
> configured in device tree by setting compatible =
> "ethernet-phy-id0180.dc81".

Why-o-why do silicon vendors make devices with invalid PHY IDs!?!?!

Did you try avoiding the compatible string. We know PHY 0 will probe
as normal. From its PHY ID we know it is a dual device. Could the
probe of PHY 0 register PHY 1?

No idea if it will work, but could nxp-tja11xx.c register is fixup for
PHY_ID_TJA1102. That fixup would do something like:

void tja1102_fixup(struct phy_device *phydev_phy0)
{
        struct mii_bus *bus = phydev_phy0->mdio.mii;
        struct phy_device *phydev_phy1;

        phydev_phy1 = phy_device_create(bus, phydev_phy0->addr + 1,
                                        PHY_ID_TJA1102, FALSE, NULL);
	if (phydev_phy1)
               phy_device_register(phydev_phy1);
}

I think the issue here is, it will deadlock when scanning for fixup
for phydev_phy1. So this basic idea, but maybe hooked in somewhere
else?

Something like this might also help vsc8584 which is a quad PHY with
some shared registers?

	  Andrew