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

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Date:   Wed, 7 Oct 2020 01:39:04 +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

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.
> > >
> > > Guenter