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    Subject[PATCH 5.6 002/177] dpaa_eth: fix usage as DSA master, try 3
    Date
    From: Vladimir Oltean <vladimir.oltean@nxp.com>

    [ Upstream commit 5d14c304bfc14b4fd052dc83d5224376b48f52f0 ]

    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.

    Actually there have already been at least 2 previous attempts to make
    this work:
    - Commit a1a50c8e4c24 ("fsl/man: Inherit parent device and of_node")
    - One or more of the patches in "[v3,0/6] adapt DPAA drivers for DSA":
    https://patchwork.ozlabs.org/project/netdev/cover/1508178970-28945-1-git-send-email-madalin.bucur@nxp.com/
    (I couldn't really figure out which one was supposed to solve the
    problem and how).

    Point being, it looks like this is still pretty much a problem today.
    On T1040, the /sys/class/net/eth0 symlink currently points to

    ../../devices/platform/ffe000000.soc/ffe400000.fman/ffe4e6000.ethernet/dpaa-ethernet.0/net/eth0

    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/net/eth0

    And this is exactly what SET_NETDEV_DEV does. It sets the parent of the
    net_device. The new parent has an of_node associated with it, and
    of_dev_node_match already checks for the of_node of the device or of its
    parent.

    Fixes: a1a50c8e4c24 ("fsl/man: Inherit parent device and of_node")
    Fixes: c6e26ea8c893 ("dpaa_eth: change device used")
    Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
    Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
    +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
    @@ -2902,7 +2902,7 @@ static int dpaa_eth_probe(struct platfor
    }

    /* 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);

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