linux-kernel - Re: [PATCH] usb: dwc3: gadget: Inform system of suspended state

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Date: Wed, 5 Jun 2024 16:41:21 +0200
From: Mike Looijmans <mike.looijmans@...ic.nl>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC: "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: gadget: Inform system of suspended state

On 05-06-2024 01:06, Thinh Nguyen wrote:
> Hi,
>
> On Tue, Jun 04, 2024, Mike Looijmans wrote:
>> On 04-06-2024 03:03, Thinh Nguyen wrote:
>>> Hi,
>>>
>>> On Mon, Jun 03, 2024, Mike Looijmans wrote:
>>>> When disconnecting the USB cable on an LS1028 device, nothing happens
>>>> in userspace, which keeps thinking everything is still up and running.
>>>> Turns out that the DWC3 controller only sends DWC3_DEVICE_EVENT_SUSPEND
>>>> in that case, and not a DWC3_DEVICE_EVENT_DISCONNECT as one would
>>>> expect. As a result, sysfs attribute "state" remains "configured"
>>>> until something resets it.
>>>>
>>>> Forward the "suspended" state to sysfs, so that the "state" at least
>>>> changes into "suspended" when one removes the cable, and hence also
>>>> matches the gadget's state when really suspended.
>>> On disconnection, did you see disconnect interrupt? If so, it should
>>> transition to USB_STATE_NOATTACHED. This change doesn't seem to directly
>>> address your issue. Can you provide the driver tracepoints?
>> The device doesn't issue a disconnect event, I didn't have tracing enabled
>> in the kernel but added some dev_info() calls to determine what was going
>> on. Added this to dwc3_process_event_entry():
>>
>> dev_info(dwc->dev, "event: 0x%x type=0x%x", event->raw, event->type.type);
>>
>> When disconnecting the cable from the host, I see this:
>>
>> [   50.841411] dwc3 3110000.usb: event: 0x6084 type=0x42
>> [   50.841457] dwc3 3110000.usb: event: 0x4086 type=0x43
>> [   50.841494] dwc3 3110000.usb: event: 0x6084 type=0x42
>> [   50.841534] dwc3 3110000.usb: event: 0x4086 type=0x43
>> [   50.841571] dwc3 3110000.usb: event: 0x4086 type=0x43
>> [   52.650990] dwc3 3110000.usb: event: 0x30601 type=0x0
>>
>> The "0x4086" and "0x6084" messages are endpoint events that occur all the
>> time while connected. The last event is the "suspend" one. After that, total
>> silence.
>>
>> If you need traces, please point me to a description on how to obtain them.
>>
>>
> Let me know if you run into issues following this instructions to
> capture the tracepoints:
> https://docs.kernel.org/driver-api/usb/dwc3.html#required-information
>
>  From the patch you provided, you only apply the change for the usb
> suspend. But did your device go through system suspend? If that's the
> case, then the dwc3 driver will cause a soft-disconnect. Currently that
> will not prompt a state change. We need the tracepoint to know more
> detail.
>
> Until we have the tracepoints, you can experiment with this test patch.
> If my suspiction is correct, then this may resolve your issue:
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 89fc690fdf34..29dbb889a0e2 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2682,6 +2682,8 @@ static int dwc3_gadget_soft_disconnect(struct dwc3 *dwc)
>           */
>          ret = dwc3_gadget_run_stop(dwc, false);
>   
> +       usb_gadget_set_state(dwc->gadget, USB_STATE_NOTATTACHED);
> +
>          /*
>           * Stop the gadget after controller is halted, so that if needed, the
>           * events to update EP0 state can still occur while the run/stop

I tried the patch above, but it doesn't work. Apparently 
dwc3_gadget_soft_disconnect() doesn't get called when I unplug the cable.

-- 

Mike Looijmans
System Expert

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