Date:   Tue, 7 Feb 2023 15:41:35 +0100
From:   =?UTF-8?B?Q2zDqW1lbnQgTMOpZ2Vy?= <clement.leger@bootlin.com>
To:     "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc:     Sergey Shtylyov <s.shtylyov@omp.ru>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
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        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Magnus Damm <magnus.damm@gmail.com>,
        Giuseppe Cavallaro <peppe.cavallaro@st.com>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Jose Abreu <joabreu@synopsys.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Wong Vee Khee <veekhee@apple.com>,
        Kurt Kanzenbach <kurt@linutronix.de>,
        Revanth Kumar Uppala <ruppala@nvidia.com>,
        Tan Tee Min <tee.min.tan@linux.intel.com>,
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        Herve Codina <herve.codina@bootlin.com>,
        =?UTF-8?B?TWlxdcOobA==?= Raynal <miquel.raynal@bootlin.com>,
        Milan Stevanovic <milan.stevanovic@se.com>,
        Jimmy Lalande <jimmy.lalande@se.com>,
        Pascal Eberhard <pascal.eberhard@se.com>,
        Mohammad Athari Bin Ismail <mohammad.athari.ismail@intel.com>,
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        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH net-next 3/6] net: stmmac: start phylink before setting
 up hardware
Message-ID: <20230207154135.6f0e59f8@fixe.home>
In-Reply-To: <Y8UsvREsKOR2ejzT@shell.armlinux.org.uk>
References: <20230116103926.276869-1-clement.leger@bootlin.com>
        <20230116103926.276869-4-clement.leger@bootlin.com>
        <Y8UsvREsKOR2ejzT@shell.armlinux.org.uk>
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Le Mon, 16 Jan 2023 10:53:49 +0000,
"Russell King (Oracle)" <linux@armlinux.org.uk> a =C3=A9crit :

> On Mon, Jan 16, 2023 at 11:39:23AM +0100, Cl=C3=A9ment L=C3=A9ger wrote:
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/driver=
s/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index f2247b8cf0a3..88c941003855 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -3818,6 +3818,12 @@ static int __stmmac_open(struct net_device *dev,
> >  		}
> >  	}
> > =20
> > +	/* We need to setup the phy & PCS before accessing the stmmac registe=
rs
> > +	 * because in some cases (RZ/N1), if the stmmac IP is not clocked by =
the
> > +	 * PCS, hardware init will fail because it lacks a RGMII RX clock.
> > +	 */
> > +	phylink_start(priv->phylink); =20
>=20
> So what happens if you end up with the mac_link_up method being called
> at this point in the driver, before the hardware has been setup ?
>=20
> If you use a fixed-link, that's a real possibility.

I actually have this setup. On the board, one GMAC is connected to a
DSA switch using a fixed-link and the other using the PCS such as added
by this series.

=46rom what I see, indeed, the mac_link_up() function is called before
stmmac_hw_setup(). This does not seems to have any effect on my setup
(except making it working of course) but I agree this is clearly not
ideal.

What I could do is adding a function in the miic pcs driver that could
be called from my rzn1 stmmac probe function to actually configure the
PCS at probe time based on the detected "phy-mode". Does that seems
better to you ?

Thanks,

--=20
Cl=C3=A9ment L=C3=A9ger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com