If "port" node is missing in PHY controller node, dwc3_get_extcon()
isn't able to find extcon devices. This is perfectly fine in case when
"usb-role-switch" or OTG is used, but next misleading error message is
printed in that case, from of_graph_get_remote_node():

    OF: graph: no port node found in /phy@1234abcd

Avoid printing that message by checking if the port node exists in PHY
node before calling of_graph_get_remote_node(). While at it, add the
comment from mentioned code block, explaining how checking the port
availability helps to avoid the misleading error.

Signed-off-by: Sam Protsenko <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
---
Changes in v4:
  - Moved the comment from patch 2/2 to 1/2
  - Fixed typos in commit message and comment
Changes in v3:
  - Split patch into two patches: logic diff and style diff

 drivers/usb/dwc3/drd.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
index 3e1c1aacf002..da428cf2eb5b 100644
--- a/drivers/usb/dwc3/drd.c
+++ b/drivers/usb/dwc3/drd.c
@@ -462,8 +462,18 @@ static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
                return edev;
        }
 
+       /*
+        * Try to get an extcon device from the USB PHY controller's "port"
+        * node. Check if it has the "port" node first, to avoid printing the
+        * error message from underlying code, as it's a valid case: extcon
+        * device (and "port" node) may be missing in case of "usb-role-switch"
+        * or OTG mode.
+        */
        np_phy = of_parse_phandle(dev->of_node, "phys", 0);
-       np_conn = of_graph_get_remote_node(np_phy, -1, -1);
+       if (of_graph_is_present(np_phy))
+               np_conn = of_graph_get_remote_node(np_phy, -1, -1);
+       else
+               np_conn = NULL;
 
        if (np_conn)
                edev = extcon_find_edev_by_node(np_conn);
-- 
2.29.2

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