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

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Date: Tue, 4 Jun 2024 07:26:48 +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 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.


>
> Thanks,
> Thinh
>
>> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
>> ---
>>
>>   drivers/usb/dwc3/gadget.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 4df2661f6675..99e8ea9db600 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -4343,6 +4343,7 @@ static void dwc3_gadget_suspend_interrupt(struct dwc3 *dwc,
>>   	if (!dwc->suspended && next == DWC3_LINK_STATE_U3) {
>>   		dwc->suspended = true;
>>   		dwc3_suspend_gadget(dwc);
>> +		usb_gadget_set_state(dwc->gadget, USB_STATE_SUSPENDED);
>>   	}
>>   
>>   	dwc->link_state = next;
>> -- 
>> 2.34.1
>>
>>
>> Met vriendelijke groet / kind regards,
>>
>> Mike Looijmans


-- 
Mike Looijmans
System Expert

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