Date:   Fri, 10 Feb 2023 12:20:38 +0100
From:   =?UTF-8?B?Q2zDqW1lbnQgTMOpZ2Vy?= <clement.leger@bootlin.com>
To:     "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc:     Clark Wang <xiaoning.wang@nxp.com>,
        Sergey Shtylyov <s.shtylyov@omp.ru>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        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>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        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>,
        Jon Hunter <jonathanh@nvidia.com>, netdev@vger.kernel.org,
        linux-renesas-soc@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        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: <20230210122038.20fab507@fixe.home>
In-Reply-To: <Y+YkhjyaL+hNGW+7@shell.armlinux.org.uk>
References: <20230116103926.276869-1-clement.leger@bootlin.com>
        <20230116103926.276869-4-clement.leger@bootlin.com>
        <Y8UsvREsKOR2ejzT@shell.armlinux.org.uk>
        <20230207154135.6f0e59f8@fixe.home>
        <Y+YkhjyaL+hNGW+7@shell.armlinux.org.uk>
Organization: Bootlin
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Le Fri, 10 Feb 2023 11:03:34 +0000,
"Russell King (Oracle)" <linux@armlinux.org.uk> a =C3=A9crit :

> On Tue, Feb 07, 2023 at 03:41:35PM +0100, Cl=C3=A9ment L=C3=A9ger wrote:
> > Le Mon, 16 Jan 2023 10:53:49 +0000,
> > "Russell King (Oracle)" <linux@armlinux.org.uk> a =C3=A9crit :
> >  =20
> > > On Mon, Jan 16, 2023 at 11:39:23AM +0100, Cl=C3=A9ment L=C3=A9ger wro=
te: =20
> > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/dr=
ivers/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 reg=
isters
> > > > +	 * 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. =20
> >=20
> > 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.
> >=20
> > From 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.
> >=20
> > 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 ? =20
>=20
> I think Clark Wang is also working on addressing a very similar problem
> with stmmac. Please can you check out his work first, he's adding a new
> function to phylink to bring the PHY up early in the resume path.
>=20
> I would like you both to work together to address what seems to be the
> same issue.
>=20

Acked

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