linux-kernel - Re: [PATCH net 2/2] dpaa_eth: fix usage as DSA master, try 4

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Message-ID: <CA+h21hqyV5RMip8etVvSWpQU0scPpXDNbMJgP9piXrn1maSMbw@mail.gmail.com>
Date:   Tue, 16 Jun 2020 18:08:15 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
Cc:     "andrew@...n.ch" <andrew@...n.ch>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "fido_max@...ox.ru" <fido_max@...ox.ru>,
        "vivien.didelot@...il.com" <vivien.didelot@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "madalin.bucur@....nxp.com" <madalin.bucur@....nxp.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net 2/2] dpaa_eth: fix usage as DSA master, try 4

On Tue, 16 Jun 2020 at 18:04, Joakim Tjernlund
<Joakim.Tjernlund@...inera.com> wrote:
>
> On Tue, 2020-06-16 at 17:56 +0300, Vladimir Oltean wrote:
> > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> >
> >
> > Hi Joakim,
> >
> > On Tue, 16 Jun 2020 at 17:51, Joakim Tjernlund
> > <Joakim.Tjernlund@...inera.com> wrote:
> > > On Tue, 2020-06-16 at 17:41 +0300, Vladimir Oltean wrote:
> > > > From: Vladimir Oltean <vladimir.oltean@....com>
> > > >
> > > > The dpaa-eth driver probes on compatible string for the MAC node, and
> > > > the fman/mac.c driver allocates a dpaa-ethernet platform device that
> > > > triggers the probing of the dpaa-eth net device driver.
> > > >
> > > > All of this is fine, but the problem is that the struct device of the
> > > > dpaa_eth net_device is 2 parents away from the MAC which can be
> > > > referenced via of_node. So of_find_net_device_by_node can't find it, and
> > > > DSA switches won't be able to probe on top of FMan ports.
> > > >
> > > > It would be a bit silly to modify a core function
> > > > (of_find_net_device_by_node) to look for dev->parent->parent->of_node
> > > > just for one driver. We're just 1 step away from implementing full
> > > > recursion.
> > > >
> > > > On T1040, the /sys/class/net/eth0 symlink currently points to:
> > > >
> > > > ../../devices/platform/ffe000000.soc/ffe400000.fman/ffe4e6000.ethernet/net/eth0
> > >
> > > Just want to point out that on 4.19.x, the above patch still exists:
> > > cd /sys
> > > find -name eth0
> > > ./devices/platform/ffe000000.soc/ffe400000.fman/ffe4e6000.ethernet/net/eth0
> > > ./class/net/eth
> > >
> >
> > By 'current' I mean 'the net tree just before this patch is applied',
> > i.e. a v5.7 tree with "dpaa_eth: fix usage as DSA master, try 3"
> > reverted.
>
> Confused, with patch reverted(and DSA working) in 4.19, I have
>   ../../devices/platform/ffe000000.soc/ffe400000.fman/ffe4e6000.ethernet/net/eth0
> Is that the wanted path? Because I figured you wanted to change it to the path further down in this email?
>
>  Jocke
> >

Yes, this is the wanted path.
The path is fine for anything below commit 060ad66f9795 ("dpaa_eth:
change DMA device"), including your v4.19.y, that's the point. By
specifying that commit in the Fixes: tag, people who deal with
backporting to stable trees know to not backport it below that commit.
So your stable tree will only get the revert patch.

-Vladimir