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

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Date:   Fri, 9 Oct 2020 02:58:01 +0000
From:   Jun Li <jun.li@....com>
To:     ChiYuan Huang <u0084500@...il.com>, 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>
Subject: RE: [PATCH] usb: typec: tcpm: Fix if vbus before cc, hard_reset_count
 not reset issue



> -----Original Message-----
> From: ChiYuan Huang <u0084500@...il.com>
> Sent: Wednesday, October 7, 2020 1:39 AM
> 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
> 
> 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.

Your patch is based on the assumption that tcpm_detach() is called with
port->attached is true, but tcpm_reset_port() may happen before that,
in that case, tcpm_reset_port() clear port->attached flag so tcpm_detach
will return directly.

> 
> > 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?

[   47.127729] Setting voltage/current limit 0 mV 0 mA
[   47.127739] polarity 0
[   47.129333] Requesting mux state 0, usb-role 0, orientation 0
[   47.130516] state change SNK_READY -> SNK_UNATTACHED
[   47.131181] CC1: 0 -> 0, CC2: 3 -> 0 [state SNK_UNATTACHED, polarity 0, disconnected]
[   47.131194] state change SNK_UNATTACHED -> PORT_RESET
[   47.134701] Setting voltage/current limit 0 mV 0 mA
[   47.134709] polarity 0
[   47.136291] Requesting mux state 0, usb-role 0, orientation 0
[   47.136873] cc:=0
[   47.137446] pending state change PORT_RESET -> PORT_RESET_WAIT_OFF @ 100 ms
[   47.138084] CC1: 0 -> 0, CC2: 0 -> 0 [state PORT_RESET, polarity 0, disconnected]
[   47.239143] state change PORT_RESET -> PORT_RESET_WAIT_OFF [delayed 100 ms]
[   47.239151] state change PORT_RESET_WAIT_OFF -> SNK_UNATTACHED
[   47.239154] Entering tcpm_detach directly return here <------------
[   47.239157] Start toggling
[   47.240150] state change SNK_UNATTACHED -> TOGGLING

Li Jun
> > 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.
> > > >
> > > > Guenter