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

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Message-ID: <79f52dae-7c16-4545-b36a-fcf481e66da5@quicinc.com>
Date: Tue, 4 Jun 2024 14:22:19 +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 1:55 PM, Mike Looijmans wrote:
> On 04-06-2024 08:45, Krishna Kurapati PSSNV wrote:
>>
>>
>> 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 ?
>>
> The board I'm testing this on is an LS1028ARDB. Looking at the 
> schematic, VBUS is routed to the chip. There's also an LED attached to 
> it, which turns off when I unplug the cable.
> 
> In the devicetree, I can't see any hint of NXP-specific "glue" in the 
> DWC3 entries, so it uses the controller "as is":
> 
>                          compatible = "fsl,ls1028a-dwc3", "snps,dwc3";
>                          reg = <0x0 0x3100000 0x0 0x10000>;
>                          snps,dis_rxdet_inp3_quirk;
>                          snps,quirk-frame-length-adjustment = <0x20>;
>                          snps,incr-burst-type-adjustment = <1>, <4>, 
> <8>, <16>;
> 
> The "fsl,ls1028a-dwc3" keyword doesn't actually occur anywhere in the 
> kernel, so it uses plain "snps,dwc3".
> 
> 
>> Also, after this happens, do you see the next plug in working ?
> 
> Next plugin works, because of a "reset" event at that point that makes 
> everything happy again.

Ahh, got it. Thanks for the info.
I ran into a similar issue before where disconnect isn't generated [1] 
and was suspecting it could be the case here but it isn't.

[1]: 
https://patchwork.kernel.org/project/linux-usb/patch/20231011100214.25720-1-quic_kriskura@quicinc.com/

Regards,
Krishna,

> 
> The state remains in "configured" while the cable is out. Plugging the 
> cable back in makes it revert to "default" first, then it goes back into 
> "configured".
>