usb: core: phy: avoid double use of 'usb3-phy'

Commit 53a2d95 ("usb: core: add phy notify connect and disconnect")
causes double use of the 'usb3-phy' in certain cases.

Since that commit, if a generic PHY named 'usb3-phy' is specified in
the device tree, that is getting added to the 'phy_roothub' list of the
secondary HCD by the usb_phy_roothub_alloc_usb3_phy() function. However,
that PHY is getting added also to the primary HCD's 'phy_roothub' list
by usb_phy_roothub_alloc() if there is no generic PHY specified with
'usb2-phy' name.

This causes that the usb_add_hcd() function executes each phy operations
twice on the 'usb3-phy'. Once when the primary HCD is added, then once
again when the secondary HCD is added.

The issue affects the Marvell Armada 3700 platform at least, where a
custom name is used for the USB2 PHY:

  $ git grep 'phy-names.*usb3' arch/arm64/boot/dts/marvell/armada-37xx.dtsi | tr '\t' ' '
  arch/arm64/boot/dts/marvell/armada-37xx.dtsi:    phy-names = "usb3-phy", "usb2-utmi-otg-phy";

Extend the usb_phy_roothub_alloc_usb3_phy() function to skip adding the
'usb3-phy' to the 'phy_roothub' list of the secondary HCD when 'usb2-phy'
is not specified in the device tree to avoid the double use.

Fixes: 53a2d95 ("usb: core: add phy notify connect and disconnect")
Cc: stable <stable@kernel.org>
Signed-off-by: Gabor Juhos <j4g8y7@gmail.com>
Link: https://patch.msgid.link/20260330-usb-avoid-usb3-phy-double-use-v1-1-d2113aecb535@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: juhosg

drivers/usb/core/phy.c

@@ -114,7 +114,7 @@ EXPORT_SYMBOL_GPL(usb_phy_roothub_alloc);
 struct usb_phy_roothub *usb_phy_roothub_alloc_usb3_phy(struct device *dev)
 {
 	struct usb_phy_roothub *phy_roothub;
-	int num_phys;
+	int num_phys, usb2_phy_index;
 
 	if (!IS_ENABLED(CONFIG_GENERIC_PHY))
 		return NULL;
@@ -124,6 +124,16 @@ struct usb_phy_roothub *usb_phy_roothub_alloc_usb3_phy(struct device *dev)
 	if (num_phys <= 0)
 		return NULL;
 
+	/*
+	 * If 'usb2-phy' is not present, usb_phy_roothub_alloc() added
+	 * all PHYs to the primary HCD's phy_roothub already, so skip
+	 * adding 'usb3-phy' here to avoid double use of that.
+	 */
+	usb2_phy_index = of_property_match_string(dev->of_node, "phy-names",
+						  "usb2-phy");
+	if (usb2_phy_index < 0)
+		return NULL;
+
 	phy_roothub = devm_kzalloc(dev, sizeof(*phy_roothub), GFP_KERNEL);
 	if (!phy_roothub)
 		return ERR_PTR(-ENOMEM);