Date:   Mon, 12 Oct 2020 14:22:47 +0800
From:   ChiYuan Huang <u0084500@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Jun Li <jun.li@....com>, Jun Li <lijun.kernel@...il.com>,
        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>
Subject: Re: [PATCH] usb: typec: tcpm: Fix if vbus before cc, hard_reset_count
 not reset issue

Guenter Roeck <linux@...ck-us.net> 於 2020年10月11日 週日 上午3:31寫道：
>
> On 10/10/20 4:21 AM, Jun Li wrote:
> >
> >
> >> -----Original Message-----
> >> From: ChiYuan Huang <u0084500@...il.com>
> >> Sent: Saturday, October 10, 2020 12:06 AM
> >> To: Jun Li <jun.li@....com>
> >> Cc: Jun Li <lijun.kernel@...il.com>; 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>
> >> Subject: Re: [PATCH] usb: typec: tcpm: Fix if vbus before cc, hard_reset_count
> >> not reset issue
> >>
> >> Jun Li <jun.li@....com> 於 2020年10月9日 週五 下午2:12寫道：
> >>>
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: ChiYuan Huang <u0084500@...il.com>
> >>>> Sent: Wednesday, October 7, 2020 6:13 PM
> >>>> 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>; Jun Li <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
> >>>
> >>> 3.
> >>> 8.3.3.3.8 PE_SNK_Hard_Reset state
> >>> "Note: The HardResetCounter is reset on a power cycle or Detach."
> >>>
> >>>>>>
> >>>>>> 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.
> >>>
> >>> Make sense.
> >>>
> >>> Then I propose doing this at SNK_UNATTACHED @@ -3156,6 +3156,7 @@
> >>> static void run_state_machine(struct tcpm_port *port)
> >>>                 if (!port->non_pd_role_swap)
> >>>                         tcpm_swap_complete(port, -ENOTCONN);
> >>>                 tcpm_pps_complete(port, -ENOTCONN);
> >>> +               port->hard_reset_count = 0;
> >>>                 tcpm_snk_detach(port);
> >>>                 if (tcpm_start_toggling(port, TYPEC_CC_RD)) {
> >>>                         tcpm_set_state(port, TOGGLING, 0); Li Jun
> >>
> >> For the current power role is snk, I think it may work.
> >> How about the src role? src role only reset the hard_reset_count in
> >> tcpm_detach and src_ready state?
> >
> > Sorry, after gave more check on PD sped, this isn't a right solution.
> > See below
> >
> >>
> >> I check the flow that  you mentioned in the previous mail. It's really a
> >> special case from any state to port_reset.
> >> If the case is considered, how about to reset  the hard_reset_count and don't
> >> care the port is attached or not in tcpm_detach function like as below.
> >>
> >> @@ -2789,6 +2789,8 @@ static void tcpm_reset_port(struct tcpm_port *port)
> >>
> >>  static void tcpm_detach(struct tcpm_port *port)  {
> >> +       port->hard_reset_count = 0;
> >> +
> >>         if (!port->attached)
> >>                 return;
> >>
> >> @@ -2797,9 +2799,6 @@ static void tcpm_detach(struct tcpm_port *port)
> >>                 port->tcpc->set_bist_data(port->tcpc, false);
> >>         }
> >>
> >> -       if (tcpm_port_is_disconnected(port))
> >> -               port->hard_reset_count = 0;
> >> -
> >>         tcpm_reset_port(port);
> >>  }
> >>
> >> Like I mentioned before, whatever the condition is, hard_reset_count must
> >> be reset to zero during tcpm_detach.
> >
> > This may not be so correct as you said, I think Guenter's concern is valid.
> >
> > tcpm_detach() is not *only* be called in cases of *physical* detach
> > like the function name suggests.
> >
> > The current proposals may *wrongly* reset this counter.
> >
> > Let me give an example:
> >
> > HARD_RESET_SEND -> HARD_RESET_START ->
> > SNK_HARD_RESET_SINK_OFF -> SNK_HARD_RESET_WAIT_VBUS ->
> > SNK_UNATTACHED(in case of VBUS doesn't come back in expected duration)
> > -> call to tcpm_detach()
> >
> > In this sequence, does the sink need keep the counter? From the PD spec,
> > I think the answer is yes, sink need this counter to judge if need
> > do hard reset again or error recovery on later try, see:
> >
> > Figure 8-67 Sink Port State Diagram
> >
> > The difference between your case and my example, is your case never turn
> > off vbus, so will not go to SNK_UNATTACHED, so will not call to tcpm_detach()
> > after first hard reset.
> >
> > So
> >       if (tcpm_port_is_disconnected(port))
> >               port->hard_reset_count = 0;
> >
> > should keep as it is, the counter can only be cleared if there is really
> > physical disconnect by *partner*.
> >
> > But current tcpm code may have some problem on keeping local CC state if
> > there is hard reset on-going(port->hard_reset_count > 0), because the
> > current handling of SNK_UNATTACHED may cause disconnection generated
> > by *local*(partner actually keeps its CC), e.g. reset polarity and do
> > drp_toggling, this should be fixed, but this is another patch, I can
> > try to do this later.
> >
> > Back to your problem, I think the issue is, at the first tcpm_detach()
> > the cc disconnect event hasn't happen, so the reset counter is left there
> > but the port->attached is cleared, then the following(real disconnect)
> > tcpm_detach() will just return directly due to port->attached is false.
> >
> > So I guess this will resolve your problem:
> >
> > @@ -2885,6 +2885,9 @@ static void tcpm_reset_port(struct tcpm_port *port)
> >
> >  static void tcpm_detach(struct tcpm_port *port)
> >  {
> > +       if (tcpm_port_is_disconnected(port))
> > +               port->hard_reset_count = 0;
> > +
> >         if (!port->attached)
> >                 return;
> >
> > @@ -2893,9 +2896,6 @@ static void tcpm_detach(struct tcpm_port *port)
> >                 port->tcpc->set_bist_data(port->tcpc, false);
> >         }
> >
> > -       if (tcpm_port_is_disconnected(port))
> > -               port->hard_reset_count = 0;
> > -
> >         tcpm_reset_port(port);
> >  }
> >
> >
I have checked this patch. It can solve the problem.

> > Compared with current code's condition:
> >    3 static bool tcpm_port_is_disconnected(struct tcpm_port *port)
> >    4 {
> >    5         return (!port->attached && port->cc1 == TYPEC_CC_OPEN &&
> >    6                 port->cc2 == TYPEC_CC_OPEN) ||
> >    7                (port->attached && ((port->polarity == TYPEC_POLARITY_CC1 &&
> >    8                                     port->cc1 == TYPEC_CC_OPEN) ||
> >    9                                    (port->polarity == TYPEC_POLARITY_CC2 &&
> >   10                                     port->cc2 == TYPEC_CC_OPEN)));
> >   11 }
> >
> > My above change is only adding another condition to clear the reset counter:
> > (!port->attached && port->cc1 == TYPEC_CC_OPEN && port->cc2 == TYPEC_CC_OPEN)
> >
> > This condition is close to Guenter's suggestion in this thread:
> >
> > -       if (tcpm_port_is_disconnected(port))
> > +       if (tcpm_port_is_disconnected(port) ||
> > +           (tcpm_cc_is_open(port->cc1) && tcpm_cc_is_open(port->cc2)))
> >
> > Hi Guenter, any comments on this?
> >
>
> That makes sense, and I would agree to the change you suggest above.
Jun:
   will you send the patch following the final discussion? Or I also can help.
Thx.
>
> Guenter
>
> > Thanks
> > Li Jun
> >
> >>
> >> But refer to Guenter's mail,  he prefer to narrow down the condition to reset
> >> this counter.
> >>
> >> I think the original thought is important why to put this line there.
> >>
> >> Hi, Guenter:
> >>    From the discussion, we really need to know why you put the reset line
> >> below port attached is false and also make some judgement.
> >> I think there may be ome condition that we don't considered.
> >
> > This condition was added at first place, I think my above
> >>
> >>>
> >>>>
> >>>>>>>>
> >>>>>>>> Guenter
>

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