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From: Wesley Cheng <wcheng@codeaurora.org>
To: balbi@kernel.org, gregkh@linuxfoundation.org
Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	Wesley Cheng <wcheng@codeaurora.org>
Subject: [PATCH] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind
Date: Thu, 16 Sep 2021 19:18:52 -0700	[thread overview]
Message-ID: <20210917021852.2037-1-wcheng@codeaurora.org> (raw)

There is a race present where the DWC3 runtime resume runs in parallel
to the UDC unbind sequence.  This will eventually lead to a possible
scenario where we are enabling the run/stop bit, without a valid
composition defined.

Thread#1 (handling UDC unbind):
usb_gadget_remove_driver()
-->usb_gadget_disconnect()
  -->dwc3_gadget_pullup(0)
--> continue UDC unbind sequence
-->Thread#2 is running in parallel here

Thread#2 (handing next cable connect)
__dwc3_set_mode()
  -->pm_runtime_get_sync()
    -->dwc3_gadget_resume()
      -->dwc->gadget_driver is NOT NULL yet
      -->dwc3_gadget_run_stop(1)
      --> _dwc3gadget_start()
...

Fix this by tracking the pullup disable routine, and avoiding resuming
of the DWC3 gadget.  Once the UDC is re-binded, that will trigger the
pullup enable routine, which would handle enabling the DWC3 gadget.

Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
---
 drivers/usb/dwc3/core.h   | 2 ++
 drivers/usb/dwc3/gadget.c | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 324ca5f5e98d..ee854697c300 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -1032,6 +1032,7 @@ struct dwc3_scratchpad_array {
  * @tx_fifo_resize_max_num: max number of fifos allocated during txfifo resize
  * @hsphy_interface: "utmi" or "ulpi"
  * @connected: true when we're connected to a host, false otherwise
+ * @softconnect: true when gadget connect is called, false when disconnect runs
  * @delayed_status: true when gadget driver asks for delayed status
  * @ep0_bounced: true when we used bounce buffer
  * @ep0_expect_in: true when we expect a DATA IN transfer
@@ -1252,6 +1253,7 @@ struct dwc3 {
 	const char		*hsphy_interface;
 
 	unsigned		connected:1;
+	unsigned		softconnect:1;
 	unsigned		delayed_status:1;
 	unsigned		ep0_bounced:1;
 	unsigned		ep0_expect_in:1;
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 804b50548163..32e01885b211 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2418,7 +2418,7 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 	int			ret;
 
 	is_on = !!is_on;
-
+	dwc->softconnect = is_on;
 	/*
 	 * Per databook, when we want to stop the gadget, if a control transfer
 	 * is still in process, complete it and get the core into setup phase.
@@ -4352,7 +4352,7 @@ int dwc3_gadget_resume(struct dwc3 *dwc)
 {
 	int			ret;
 
-	if (!dwc->gadget_driver)
+	if (!dwc->gadget_driver || !dwc->softconnect)
 		return 0;
 
 	ret = __dwc3_gadget_start(dwc);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project


             reply	other threads:[~2021-09-17  2:19 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17  2:18 Wesley Cheng [this message]
2021-09-17  5:17 ` Felipe Balbi
2021-09-17  6:28   ` Wesley Cheng
2021-09-17  9:37     ` Felipe Balbi

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