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

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On Wed, Jun 05, 2024, Mike Looijmans wrote:
> 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://urldefense.com/v3/__https://docs.kernel.org/driver-api/usb/dwc3.html*required-information__;Iw!!A4F2R9G_pg!bahfjil5HEUq-fOHAwDfusutLJCLognfyLHTFLiSlVuZotpr99XBGg7nB0zRRnNF_M1pqEKcVa4KxNJwh3_F2dZWwVKTkUY$
> I've attached the traces as a tarball. Hope it survives.

Got them. Thanks.

> 
> At the start, the USB is up and running (and doing ethernet+mass storage). I
> saved the trace after pulling the USB cable.
> 

From the capture, we can see that there's no system suspend, so there's
no soft-disconnect.

Base on the suspend event, you're running in usb2 speed (ignore the
incorrect U3 state, should be L2):

	irq/94-dwc3-631     [000] D..1.   149.139290: dwc3_event: event (00030601): Suspend [U3]

The DSTS from the regdump indicated that you're still in L2 despite
disconnected. Looks like the phy was unable to detect and wakeup from
the disconnection to notify the controller.

Can you experiment with setting "snps,dis_u2_susphy_quirk" to disable
usb2 phy suspend.

Does your device support SuperSpeed? If so, do you observe the same
behavior while operating in SuperSpeed?

Thanks,
Thinh