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

[Joakim Tjernlund]

On Tue, 2020-06-16 at 17:56 +0300, Vladimir Oltean wrote:
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> 
> 
> Hi Joakim,
> 
> On Tue, 16 Jun 2020 at 17:51, Joakim Tjernlund
> <Joakim.Tjernlund@xxxxxxxxxxxx> wrote:
> > On Tue, 2020-06-16 at 17:41 +0300, Vladimir Oltean wrote:
> > > From: Vladimir Oltean <vladimir.oltean@xxxxxxx>
> > > 
> > > 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
> 
> > > which pretty much illustrates the problem. The closest of_node we've got
> > > is the "fsl,fman-memac" at /soc@ffe000000/fman@400000/ethernet@e6000,
> > > which is what we'd like to be able to reference from DSA as host port.
> > > 
> > > For of_find_net_device_by_node to find the eth0 port, we would need the
> > > parent of the eth0 net_device to not be the "dpaa-ethernet" platform
> > > device, but to point 1 level higher, aka the "fsl,fman-memac" node
> > > directly. The new sysfs path would look like this:
> > > 
> > > ../../devices/platform/ffe000000.soc/ffe400000.fman/ffe4e6000.ethernet/dpaa-ethernet.0/net/eth0
> > > 
> > > Actually this has worked before, through the SET_NETDEV_DEV mechanism,
> > > which sets the parent of the net_device as the parent of the platform
> > > device. But the device which was set as sysfs parent was inadvertently
> > > changed through commit 060ad66f9795 ("dpaa_eth: change DMA device"),
> > > which did not take into consideration the effect it would have upon
> > > of_find_net_device_by_node. So restore the old sysfs parent to make that
> > > work correctly.
> > > 
> > > Fixes: 060ad66f9795 ("dpaa_eth: change DMA device")
> > > Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
> > > ---
> > >  drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > index c4416a5f8816..2972244e6eb0 100644
> > > --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > @@ -2914,7 +2914,7 @@ static int dpaa_eth_probe(struct platform_device *pdev)
> > >         }
> > > 
> > >         /* Do this here, so we can be verbose early */
> > > -       SET_NETDEV_DEV(net_dev, dev);
> > > +       SET_NETDEV_DEV(net_dev, dev->parent);
> > >         dev_set_drvdata(dev, net_dev);
> > > 
> > >         priv = netdev_priv(net_dev);
> > > --
> > > 2.25.1
> > > 
> 
> Thanks,
> -Vladimir