[PATCH v2 1/2] usb: misc: onboard_usb_hub: Don't create platform devices for DT nodes without 'vdd-supply'

[Matthias Kaehlcke <mka@chromium.org>]

The primary task of the onboard_usb_hub driver is to control the
power of an onboard USB hub. The driver gets the regulator from the
device tree property "vdd-supply" of the hub's DT node. Some boards
have device tree nodes for USB hubs supported by this driver, but
don't specify a "vdd-supply". This is not an error per se, it just
means that the onboard hub driver can't be used for these hubs, so
don't create platform devices for such nodes.

This change doesn't completely fix the reported regression. It
should fix it for the RPi 3 B Plus and boards with similar hub
configurations (compatible DT nodes without "vdd-supply"), boards
that actually use the onboard hub driver could still be impacted
by the race conditions discussed in that thread. Not creating the
platform devices for nodes without "vdd-supply" is the right
thing to do, independently from the race condition, which will
be fixed in future patch.

Fixes: 8bc063641ceb ("usb: misc: Add onboard_usb_hub driver")
Link: https://lore.kernel.org/r/d04bcc45-3471-4417-b30b-5cf9880d785d@i2se.com/
Reported-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---

Changes in v2:
- don't create platform devices when "vdd-supply" is missing,
  rather than returning an error from _find_onboard_hub()
- check for "vdd-supply" not "vdd" (Johan)
- updated subject and commit message
- added 'Link' tag (regzbot)

 drivers/usb/misc/onboard_usb_hub_pdevs.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/usb/misc/onboard_usb_hub_pdevs.c b/drivers/usb/misc/onboard_usb_hub_pdevs.c
index ed22a18f4ab7..8cea53b0907e 100644
--- a/drivers/usb/misc/onboard_usb_hub_pdevs.c
+++ b/drivers/usb/misc/onboard_usb_hub_pdevs.c
@@ -101,6 +101,19 @@ void onboard_hub_create_pdevs(struct usb_device *parent_hub, struct list_head *p
 			}
 		}
 
+		/*
+		 * The primary task of the onboard_usb_hub driver is to control
+		 * the power of an USB onboard hub. Some boards have device tree
+		 * nodes for USB hubs supported by this driver, but don't
+		 * specify a "vdd-supply", which is needed by the driver. This is
+		 * not a DT error per se, it just means that the onboard hub
+		 * driver can't be used with these nodes, so don't create a
+		 * a platform device for such a node.
+		 */
+		if (!of_get_property(np, "vdd-supply", NULL) &&
+		    !of_get_property(npc, "vdd-supply", NULL))
+			goto node_put;
+
 		pdev = of_platform_device_create(np, NULL, &parent_hub->dev);
 		if (!pdev) {
 			dev_err(&parent_hub->dev,
-- 
2.39.0.314.g84b9a713c41-goog