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    Subject[PATCH 5.15 005/148] usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind
    Date
    From: Wesley Cheng <wcheng@codeaurora.org>

    [ Upstream commit 8217f07a50236779880f13e87f99224cd9117f83 ]

    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.

    Acked-by: Felipe Balbi <balbi@kernel.org>
    Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
    Link: https://lore.kernel.org/r/20210917021852.2037-1-wcheng@codeaurora.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Stable-dep-of: 040f2dbd2010 ("usb: dwc3: gadget: Avoid duplicate requests to enable Run/Stop")
    Signed-off-by: Sasha Levin <sashal@kernel.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 fd5d42ec5350..dbae57725f52 100644
    --- a/drivers/usb/dwc3/core.h
    +++ b/drivers/usb/dwc3/core.h
    @@ -1028,6 +1028,7 @@ 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
    @@ -1247,6 +1248,7 @@ 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 322754a7f91c..5f9a0ab09f4b 100644
    --- a/drivers/usb/dwc3/gadget.c
    +++ b/drivers/usb/dwc3/gadget.c
    @@ -2442,7 +2442,7 @@ 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.
    @@ -4421,7 +4421,7 @@ 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);
    --
    2.35.1


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