linux-kernel - Re: [PATCH] usb: typec: tcpm: Fix if vbus before cc, hard_reset

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Date:   Wed, 7 Oct 2020 18:13:03 +0800
From:   ChiYuan Huang <u0084500@...il.com>
To:     Jun Li <lijun.kernel@...il.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Greg KH <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Linux USB List <linux-usb@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        cy_huang <cy_huang@...htek.com>, Li Jun <jun.li@....com>
Subject: Re: [PATCH] usb: typec: tcpm: Fix if vbus before cc, hard_reset_count
 not reset issue

ChiYuan Huang <u0084500@...il.com> 於 2020年10月7日 週三 上午1:39寫道：
>
> Jun Li <lijun.kernel@...il.com> 於 2020年10月7日 週三 上午12:52寫道：
> >
> > ChiYuan Huang <u0084500@...il.com> 于2020年10月6日周二 下午12:38写道：
> > >
> > > Guenter Roeck <linux@...ck-us.net> 於 2020年10月5日 週一 下午11:30寫道：
> > > >
> > > > On 10/5/20 4:08 AM, Greg KH wrote:
> > > > [ ... ]
> > > > >>> What ever happened with this patch, is there still disagreement?
> > > > >>>
> > > > >>
> > > > >> Yes, there is. I wouldn't have added the conditional without reason,
> > > > >> and I am concerned that removing it entirely will open another problem.
> > > > >> Feel free to apply, though - I can't prove that my concern is valid,
> > > > >> and after all we'll get reports from the field later if it is.
> > > > >
> > > > > Ok, can I get an ack so I know who to come back to in the future if
> > > > > there are issues?  :)
> > > > >
> > > >
> > > > Not from me, for the reasons I stated. I would be ok with something like:
> > > >
> > > > -       if (tcpm_port_is_disconnected(port))
> > > > +       if (tcpm_port_is_disconnected(port) ||
> > > > +           (tcpm_cc_is_open(port->cc1) && tcpm_cc_is_open(port->cc2)))
> > > >
> > > > to narrow down the condition.
> > >
> > > I have tried the above comment and It doesn't work.
> > > How about to change the judgement like as below
> > >
> > > -       if (tcpm_port_is_disconnected(port))
> > > +       if (tcpm_port_is_disconnected(port) || !port->vbus_present)
> > >
> > > The hard_reset_count not reset issue is following by the below order
> > > 1. VBUS off ( at the same time, cc is still detected as attached)
> > > port->attached become false and cc is not open
> > > 2. After that, cc detached.
> > > due to port->attached is false, tcpm_detach() directly return.
> >
> > If tcpm_detach() return directly, then how your patch can reset
> > hard_reset_count?
> >
> Yes, it can. We know vbus_present change from true to false and cc
> detach both trigger tcpm_detach.
> My change is whenever tcpm_detach to be called, hard_reset_count will
> be reset to zero.
>
> > I am seeing the same issue on my platform, the proposed change:
> > -       if (tcpm_port_is_disconnected(port))
> > -               port->hard_reset_count = 0;
> > +       port->hard_reset_count = 0;
> > can't resolve it on my platform.
> >
> I'm not sure what's your condition. Could you directly paste the tcpm
> log for the check?
> > How about reset hard_reset_count in SNK_READY?
> > @@ -3325,6 +3329,7 @@ static void run_state_machine(struct tcpm_port *port)
> >         case SNK_READY:
> >                 port->try_snk_count = 0;
> >                 port->update_sink_caps = false;
> > +               port->hard_reset_count = 0;
> >                 if (port->explicit_contract) {
> >                         typec_set_pwr_opmode(port->typec_port,
> >                                              TYPEC_PWR_MODE_PD);
> >
> > can this resolve your problem?
> I'm not sure. It need to have a try, then I can answer you.
> But from USBPD spec, the hard_reset_count need to reset zero only when
> 1. At src state, pe_src_send_cap and receive GoodCRC
> 2. At snk state, pe_snk_evaluate_cap need to reset hard_reset_count
> >
> > Li Jun
> > >
> > > And that's why hard_reset_count is not reset to 0.

I tried in snk_ready to reset hard_reset_count.
At normal case, it works.
But it seems still the possible fail case like as below.
200ms -> cc debounce max time
240ms -> snk_waitcap max time
If the plugin/out period is between (200+240) and (200+ 2* 240)ms ,
and the src side plug out like as the described scenario.
>From this case, hard_reset_count may still 1.
And we expect the next plugin hard_reset_count is 0. But not, actually
it never reset.
So at next plugin, only one hard_reset will be sent and reach
hard_reset_count max (2).

This case is hard to reproduce. But actually it's possible.

> > > >
> > > > Guenter