usb: host: xhci-plat: Prevent an abnormally restrictive PHY init skipping

In the past, USB PHY handling has been moved in the HCD core. Some
host controller drivers needing more control of the PHYs, they have
been granted the freedom to handle themselves the PHY states and to
prevent the HCD core to do so in commit 4e88d4c083 ("usb: add a flag
to skip PHY initialization to struct usb_hcd"). With this change, any
USB host controller could set the hcd->skip_phy_initialization flag so
that the HCD core would just skip the PHY initialization sequence.

However, in the USB subsystem, there are currently two entirely
different forms of PHY: one is called 'usb_phy' and is
USB-subsystem-wide, while there is also the generic and kernel-wide
'phy' from the (recent) generic PHY framework.

When the commit above was introduced, both type of PHYs where handled
by the HCD core.

Later, commit bc40f53417 ("USB: core: hcd: drop support for legacy
phys") removed the support for the former type of PHYs in the HCD
core. These 'usb_phy' are still present though, but managed from the
controller drivers only. Hence, setting the
hcd->skip_phy_initialization flag just because a 'usb_phy' is
initialized by a controller driver is a non-sense.

For instance on Armada CP110, a 'usb_phy' is there to enable the power
supply to the USB host, while there is also a COMPHY block providing
SERDES lanes configuration that is referenced as a PHY from the common
PHY framework.

Right now, users of the xhci-plat.c driver either use a 'usb_phy' only
and do not care about the attempt of generic PHY initialization within
the HCD core (as there is none); or they use a single 'phy' and the
code flow does not pass through the block setting
hcd->skip_phy_initialization anyway.

While there is not users of both PHY types at the same time, drop this
limitation from the xhci-plat.c driver. Note that the tegra driver
probably has the same limitation and could definitely benefit from a
similar change.

Cc: Johan Hovold <johan@kernel.org>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20190731121150.2253-1-miquel.raynal@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-plat.c

@@ -307,7 +307,6 @@ static int xhci_plat_probe(struct platform_device *pdev)
 		ret = usb_phy_init(hcd->usb_phy);
 		if (ret)
 			goto put_usb3_hcd;
-		hcd->skip_phy_initialization = 1;
 	}
 
 	hcd->tpl_support = of_usb_host_tpl_support(sysdev->of_node);