Re: [PATCH v2 2/2] Revert "usb: dwc3: Don't switch OTG -> peripheral if extcon is present"

Thinh Nguyen
2022-10-07T02:12:03Z

On Thu, Oct 06, 2022, Ferry Toth wrote:
> Hi
>
> On 06-10-2022 04:12, Thinh Nguyen wrote:
> > On Wed, Oct 05, 2022, Ferry Toth wrote:
> > > Hi,
> > >
> > > Thanks!
> > >
> > > Does the failure only happen the first time host is initialized? Or can
> > > it recover after switching to device then back to host mode?
> > >
> > > I can switch back and forth and device mode works each time, host mode remains
> > > dead.
> > Ok.
> >
> > > Probably the failure happens if some step(s) in dwc3_core_init() hasn't
> > > completed.
> > >
> > > tusb1210 is a phy driver right? The issue is probably because we didn't
> > > initialize the phy yet. So, I suspect placing dwc3_get_extcon() after
> > > initializing the phy will probably solve the dependency problem.
> > >
> > > You can try something for yourself or I can provide something to test
> > > later if you don't mind (maybe next week if it's ok).
> > >
> > > Yes, the code move I mentioned above "moves dwc3_get_extcon() until after
> > > dwc3_core_init() but just before dwc3_core_init_mode(). AFAIU initially
> > > dwc3_get_extcon() was called from within dwc3_core_init_mode() but only for
> > > case USB_DR_MODE_OTG. So with this change order of events is more or less
> > > unchanged" solves the issue.
> > >
> > I saw the experiment you did from the link you provided. We want to also
> > confirm exactly which step in dwc3_core_init() was needed.
>
> Ok. I first tried the code move suggested by Andrey (didn't work). Then
> after reading the actual code I moved a bit further.
>
> This move was on top of -rc6 without any reverts. I did not make additional
> changes to dwc3_core_init()
>
> So current v6.0 has: dwc3_get_extcon - dwc3_get_dr_mode - ... -
> dwc3_core_init - .. - dwc3_core_init_mode (not working)
>
> I changed to: dwc3_get_dr_mode - dwc3_get_extcon - .. - dwc3_core_init - ..
> - dwc3_core_init_mode (no change)
>
> Then to: dwc3_get_dr_mode - .. - dwc3_core_init - .. - dwc3_get_extcon -
> dwc3_core_init_mode (works)
>
> .. are what I believe for this issue irrelevant calls to
> dwc3_alloc_scratch_buffers, dwc3_check_params and dwc3_debugfs_init.
>

Right. Thanks for narrowing it down. There are still many steps in
dwc3_core_init(). We have some suspicion, but we still haven't confirmed
the exact cause of the failure. We can write a proper patch once we know
the reason.

Thanks,
Thinh