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

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Message-ID: <91b3af13-e723-4a49-b7f6-06f927c286c9@quicinc.com>
Date: Tue, 4 Jun 2024 12:15:53 +0530
From: Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
To: Mike Looijmans <mike.looijmans@...ic.nl>,
        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 6/4/2024 10:56 AM, 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.
> 
> 

Hi Mike,

  I may be wrong, but can you help understand the mechanism as to how 
disconnect interrupt is generated in your targets. For example, on QC 
SoC's, this happens when HS_PHY_CTRL reg VBUS_VALID bit is cleared and 
cable is disconnected. This is because the vbus line is not routed to 
controller. But from my calls with Synopsys previously, I remember that 
the vbus line is routed to the controller as well for other OEMs. In 
your SoC, what is the indication to controller that vbus is absent ?

Also, after this happens, do you see the next plug in working ?

Regards,
Krishna,