[PATCH] usb: dwc3: gadget: Queue PM runtime idle on disconnect event

[PATCH] usb: dwc3: gadget: Queue PM runtime idle on disconnect event

[Wesley Cheng]

There is a scenario where DWC3 runtime suspend is blocked due to the
dwc->connected flag still being true while PM usage_count is zero after
DWC3 giveback is completed and the USB gadget session is being terminated.
This leads to a case where nothing schedules a PM runtime idle for the
device.

The exact condition is seen with the following sequence:
  1.  USB bus reset is issued by the host
  2.  Shortly after, or concurrently, a USB PD DR SWAP request is received
      (sink->source)
  3.  USB bus reset event handler runs and issues
      dwc3_stop_active_transfers(), and pending transfer are stopped
  4.  DWC3 usage_count decremented to 0, and runtime idle occurs while
      dwc->connected == true, returns -EBUSY
  5.  DWC3 disconnect event seen, dwc->connected set to false due to DR
      swap handling
  6.  No runtime idle after this point

Address this by issuing an asynchronous PM runtime idle call after the
disconnect event is completed, as it modifies the dwc->connected flag,
which is what blocks the initial runtime idle.

Fixes: fc8bb91bc83e ("usb: dwc3: implement runtime PM")
Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
---
 drivers/usb/dwc3/gadget.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 858fe4c299b7..de6056277f94 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -3973,6 +3973,13 @@ static void dwc3_gadget_disconnect_interrupt(struct dwc3 *dwc)
 	usb_gadget_set_state(dwc->gadget, USB_STATE_NOTATTACHED);
 
 	dwc3_ep0_reset_state(dwc);
+
+	/*
+	 * Request PM idle to address condition where usage count is
+	 * already decremented to zero, but waiting for the disconnect
+	 * interrupt to set dwc->connected to FALSE.
+	 */
+	pm_request_idle(dwc->dev);
 }
 
 static void dwc3_gadget_reset_interrupt(struct dwc3 *dwc)

Re: [PATCH] usb: dwc3: gadget: Queue PM runtime idle on disconnect event

[Greg KH]

On Tue, Jan 02, 2024 at 06:30:23PM -0800, Wesley Cheng wrote:
> There is a scenario where DWC3 runtime suspend is blocked due to the
> dwc->connected flag still being true while PM usage_count is zero after
> DWC3 giveback is completed and the USB gadget session is being terminated.
> This leads to a case where nothing schedules a PM runtime idle for the
> device.
> 
> The exact condition is seen with the following sequence:
>   1.  USB bus reset is issued by the host
>   2.  Shortly after, or concurrently, a USB PD DR SWAP request is received
>       (sink->source)
>   3.  USB bus reset event handler runs and issues
>       dwc3_stop_active_transfers(), and pending transfer are stopped
>   4.  DWC3 usage_count decremented to 0, and runtime idle occurs while
>       dwc->connected == true, returns -EBUSY
>   5.  DWC3 disconnect event seen, dwc->connected set to false due to DR
>       swap handling
>   6.  No runtime idle after this point
> 
> Address this by issuing an asynchronous PM runtime idle call after the
> disconnect event is completed, as it modifies the dwc->connected flag,
> which is what blocks the initial runtime idle.
> 
> Fixes: fc8bb91bc83e ("usb: dwc3: implement runtime PM")
> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> ---
>  drivers/usb/dwc3/gadget.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 858fe4c299b7..de6056277f94 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -3973,6 +3973,13 @@ static void dwc3_gadget_disconnect_interrupt(struct dwc3 *dwc)
>  	usb_gadget_set_state(dwc->gadget, USB_STATE_NOTATTACHED);
>  
>  	dwc3_ep0_reset_state(dwc);
> +
> +	/*
> +	 * Request PM idle to address condition where usage count is
> +	 * already decremented to zero, but waiting for the disconnect
> +	 * interrupt to set dwc->connected to FALSE.
> +	 */
> +	pm_request_idle(dwc->dev);
>  }
>  
>  static void dwc3_gadget_reset_interrupt(struct dwc3 *dwc)

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
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