[PATCH] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind

[PATCH] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind

[Wesley Cheng]

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

Re: [PATCH] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind

[Felipe Balbi]

Hi,

Wesley Cheng <wcheng@codeaurora.org> writes:

> 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>

This looks okay to me, but needs to be tested by a few folks ;-)

Acked-by: Felipe Balbi <balbi@kernel.org>

-- 
balbi

Re: [PATCH] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind

[Wesley Cheng]

Hi,

On 9/16/2021 10:17 PM, Felipe Balbi wrote:
> 
> Hi,
> 
> Wesley Cheng <wcheng@codeaurora.org> writes:
> 
>> 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>

Thanks, Felipe!

> 
> This looks okay to me, but needs to be tested by a few folks ;-)
> 
> Acked-by: Felipe Balbi <balbi@kernel.org>
> 
Yes, would be good to get some functions using
usb_gadget_activate/deactivate().  It should be OK for those situations
as well, but just to make sure :)

Thanks
Wesley Cheng
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind

[Felipe Balbi]

Wesley Cheng <wcheng@codeaurora.org> writes:

> Hi,
>
> On 9/16/2021 10:17 PM, Felipe Balbi wrote:
>> 
>> Hi,
>> 
>> Wesley Cheng <wcheng@codeaurora.org> writes:
>> 
>>> 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>
>
> Thanks, Felipe!
>
>> 
>> This looks okay to me, but needs to be tested by a few folks ;-)
>> 
>> Acked-by: Felipe Balbi <balbi@kernel.org>
>> 
> Yes, would be good to get some functions using
> usb_gadget_activate/deactivate().  It should be OK for those situations
> as well, but just to make sure :)

IIRC, the UVC function relies on those. You could give it a shot ;-)

-- 
balbi