linux-imx

MLK-11051 net: phy: mdio_bus: don't call .phy_suspendi() when netdev is NULL

In .mdio_bus_phy_may_suspend(), there check netdev is NULL to judge to set
phy to suspend status.

netdev is NULL has three cases:
- phy is not found
- phy is found, match to general phy driver
- phy is found, match to specifical phy driver

Case 1: phy is not found, cannot communicate by MDIO bus.
Case 2: phy is found:
        if phy dev driver probe/bind err, netdev is not __open__ status,
           mdio bus is unregistered.
        if phy is detached, phy had entered suspended status.
Case 3: phy is found, phy is detached, phy had entered suspended status.

So, in here, it shouldn't set phy to suspend by calling mdio bus.

In i.MX6UL evk/arm2 board, if down the ethx interface and do
suspend/resume, system will hang. Because after ethx down all clocks are
gated off, for general phy driver, unbind the phy device, for specifical
phy driver, no unbind the device, and the original driver call mdio bus to
set phy to suspend during system suspend, so system will hang since there
have mdio register access.
The patch can fix it.

Signed-off-by: Fugang Duan <B38611@freescale.com>