linux-kernel - [PATCH] usb: dwc2: gadget: remove of_node reference upon udc

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Message-ID: <20250124173325.2747710-1-fabrice.gasnier@foss.st.com>
Date: Fri, 24 Jan 2025 18:33:25 +0100
From: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
To: <hminas@...opsys.com>, <gregkh@...uxfoundation.org>
CC: <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <fabrice.gasnier@...s.st.com>
Subject: [PATCH] usb: dwc2: gadget: remove of_node reference upon udc_stop

In dwc2_hsotg_udc_start(), e.g. when binding composite driver, "of_node"
is set to hsotg->dev->of_node.

It causes errors when binding the gadget driver several times, on
stm32mp157c-ev1 board. Below error is seen:
"pin PA10 already requested by 49000000.usb-otg; cannot claim for gadget.0"

The first time, no issue is seen as when registering the driver, of_node
isn't NULL:
-> gadget_dev_desc_UDC_store
  -> usb_gadget_register_driver_owner
    -> driver_register
    ...
      -> really_probe -> pinctrl_bind_pins (no effect)

Then dwc2_hsotg_udc_start() sets of_node.

The second time (stop the gadget, reconfigure it, then start it again),
of_node has been set, so the probing code tries to acquire pins for the
gadget. These pins are hold by the controller, hence the error.

So clear gadget.dev.of_node in udc_stop() routine to avoid the issue.

Fixes: 7d7b22928b90 ("usb: gadget: s3c-hsotg: Propagate devicetree to gadget drivers")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
---
Note: I'd have been tempted to remove of_node setting from udc_start:
 -	hsotg->gadget.dev.of_node = hsotg->dev->of_node;

I can't find the original code that parses the device node [1] from
composite_bind() routine, originally part of the series that introduces
this.
I'm not sure if setting the gadget of_node is really useful, but I chose
safe approach to simply clear it in udc_stop().

[1] http://lore.kernel.org/lkml/1340720833-781-6-git-send-email-aletes.xgr@gmail.com/
---
 drivers/usb/dwc2/gadget.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index e7bf9cc635be..bd4c788f03bc 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -4615,6 +4615,7 @@ static int dwc2_hsotg_udc_stop(struct usb_gadget *gadget)
 	spin_lock_irqsave(&hsotg->lock, flags);

 	hsotg->driver = NULL;
+	hsotg->gadget.dev.of_node = NULL;
 	hsotg->gadget.speed = USB_SPEED_UNKNOWN;
 	hsotg->enabled = 0;

-- 
2.25.1