lkml.org 
[lkml]   [2021]   [Sep]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind
From
Date
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

\
 
 \ /
  Last update: 2021-09-17 08:29    [W:0.311 / U:0.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site