RE: [PATCH] usb: typec: tcpm: Fix if vbus before cc, hard_reset_count not reset issue

[Jun Li]

> -----Original Message-----
> From: ChiYuan Huang <u0084500@xxxxxxxxx>
> Sent: Wednesday, October 7, 2020 6:13 PM
> To: Jun Li <lijun.kernel@xxxxxxxxx>
> Cc: Guenter Roeck <linux@xxxxxxxxxxxx>; Greg KH
> <gregkh@xxxxxxxxxxxxxxxxxxx>; Heikki Krogerus
> <heikki.krogerus@xxxxxxxxxxxxxxx>; Linux USB List
> <linux-usb@xxxxxxxxxxxxxxx>; lkml <linux-kernel@xxxxxxxxxxxxxxx>;
> cy_huang <cy_huang@xxxxxxxxxxx>; Jun Li <jun.li@xxxxxxx>
> Subject: Re: [PATCH] usb: typec: tcpm: Fix if vbus before cc, hard_reset_count
> not reset issue
> 
> ChiYuan Huang <u0084500@xxxxxxxxx> 於 2020年10月7日 週三 上午1:39寫道：
> >
> > Jun Li <lijun.kernel@xxxxxxxxx> 於 2020年10月7日 週三 上午12:52寫道：
> > >
> > > ChiYuan Huang <u0084500@xxxxxxxxx> 于2020年10月6日周二 下午12:38写
> 道：
> > > >
> > > > Guenter Roeck <linux@xxxxxxxxxxxx> 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

> 
> > > > >
> > > > > Guenter