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From:   "Sriram Dash" <sriram.dash@samsung.com>
To:     "'Robin Murphy'" <robin.murphy@arm.com>,
        "'Florian Fainelli'" <f.fainelli@gmail.com>,
        <netdev@vger.kernel.org>, <narmstrong@baylibre.com>,
        "'Heiko Stuebner'" <heiko@sntech.de>
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        "'David S. Miller'" <davem@davemloft.net>,
        <linux-arm-kernel@lists.infradead.org>, <heiko@sntech.de>
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Subject: RE: [PATCH net] Revert
 "net: stmmac: platform: Fix MDIO init for platforms without PHY"
Date:   Tue, 7 Jan 2020 17:44:19 +0530
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> From: Robin Murphy <robin.murphy=40arm.com>
> Subject: Re: =5BPATCH net=5D Revert =22net: stmmac: platform: Fix MDIO in=
it for
> platforms without PHY=22
>=20
> On 07/01/2020 5:46 am, Sriram Dash wrote:
> >> From: Florian Fainelli <f.fainelli=40gmail.com>
> >> Subject: =5BPATCH net=5D Revert =22net: stmmac: platform: Fix MDIO ini=
t for
> > platforms
> >> without PHY=22
> >>
> >> This reverts commit d3e014ec7d5ebe9644b5486bc530b91e62bbf624 (=22net:
> >> stmmac: platform: Fix MDIO init for platforms without PHY=22) because
> >> it
> > breaks
> >> existing systems with stmmac which do not have a MDIO bus sub-node
> >> nor a 'phy-handle' property declared in their Device Tree. On those
> >> systems, the stmmac MDIO bus is expected to be created and then
> >> scanned by
> >> of_mdiobus_register() to create PHY devices.
> >>
> >> While these systems should arguably make use of a more accurate
> >> Device
> > Tree
> >> reprensentation with the use of the MDIO bus sub-node an appropriate
> >> 'phy- handle', we cannot break them, therefore restore the behavior
> >> prior to the
> > said
> >> commit.
> >>
> >> Fixes: d3e014ec7d5e (=22net: stmmac: platform: Fix MDIO init for
> >> platforms without PHY=22)
> >> Reported-by: Heiko Stuebner <heiko=40sntech.de>
> >> Reported-by: kernelci.org bot <bot=40kernelci.org>
> >> Signed-off-by: Florian Fainelli <f.fainelli=40gmail.com>
> > Nacked-by: Sriram Dash <Sriram.dash=40samsung.com>
> >
> >> ---
> >> Heiko,
> >>
> >> I did not add the Tested-by because the patch is a little bit
> >> different
> > from what
> >> you tested, even if you most likely were not hitting the other part
> >> that I
> > was
> >> changing. Thanks=21
> >>
> >>   drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c =7C 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> >> b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> >> index cc8d7e7bf9ac..bedaff0c13bd 100644
> >> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> >> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> >> =40=40 -320,7 +320,7 =40=40 static int stmmac_mtl_setup(struct
> >> platform_device *pdev,  static int stmmac_dt_phy(struct
> plat_stmmacenet_data *plat,
> >>   			 struct device_node *np, struct device *dev)  =7B
> >> -	bool mdio =3D false;
> >> +	bool mdio =3D true;
> >
> >
> > This is breaking for the platforms with fixed-link.
> > stih418-b2199.dts and 169445.dts to name a few.
> >
> > For the newer platforms, they should provide the mdio/ snps,dwmac-mdio
> > property in the device tree as we are checking the mdio/
> > snps,dwmac-mdio property in the stmmac_platform driver for the mdio bus
> memory allocation.
> > For existing platforms, I agree we should not break them, but we
> > should make the code correct. And make the existing platforms adapt to =
the
> proper code.
> > There is a proposed solution.
> > https://protect2.fireeye.com/url?k=3Dd075c0fc-8da69942-d0744bb3-0cc47a3=
1
> > ba82-60be9f5a0fb38a27&u=3Dhttps://lkml.org/lkml/2020/1/7/14
> >
> > What do you think?
>=20
> The binding says that the phy handle and mdio child node are optional, so
> =22update all of the DTBs=21=22 is not a viable solution. I'm far from an=
 expert here, but

I get your point Robin. Because the mdio child or snps,dwmac-mdio is not ma=
ndatory,
there has been this problem.

> AFAICS the fault of the current code is that it assumes the lack of a phy=
 handle
> implies a fixed link, so the obvious answer is to actually check whether =
the

Kind of.=20

> =22fixed-link=22 property is present.


I agree to have a fixed link check. Possibly this can be done:

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
=40=40 -320,7 +320,9 =40=40 static int stmmac_mtl_setup(struct platform_dev=
ice *pdev,
 static int stmmac_dt_phy(struct plat_stmmacenet_data *plat,
                         struct device_node *np, struct device *dev)
 =7B
-       bool mdio =3D false;
+       bool mdio =3D true;
+       struct device_node *fixed_link;
+
        static const struct of_device_id need_mdio_ids=5B=5D =3D =7B
                =7B .compatible =3D =22snps,dwc-qos-ethernet-4.10=22 =7D,
                =7B=7D,
=40=40 -340,9 +342,8 =40=40 static int stmmac_dt_phy(struct plat_stmmacenet=
_data *plat,
                =7D
        =7D

-       if (plat->mdio_node) =7B
-               dev_dbg(dev, =22Found MDIO subnode=5Cn=22);
-               mdio =3D true;
+       if (of_get_child_by_name(np, =22fixed-link=22)) =7B
+               mdio =3D false;
        =7D

        if (mdio) =7B

Neil and Heiko,

Can you guys please test this on your platforms?
We can post a more cleaner version of the patch if all agree to it.

>=20
> Robin.
>=20
> >
> >>   	static const struct of_device_id need_mdio_ids=5B=5D =3D =7B
> >>   		=7B .compatible =3D =22snps,dwc-qos-ethernet-4.10=22 =7D,
> >>   		=7B=7D,
> >> --
> >> 2.19.1
> >
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel=40lists.infradead.org
> > https://protect2.fireeye.com/url?k=3D2cb95551-716a0cef-2cb8de1e-0cc47a3=
1
> > ba82-d01ceb62a8a93fa2&u=3Dhttp://lists.infradead.org/mailman/listinfo/l=
i
> > nux-arm-kernel
> >