Date:   Sat, 10 Oct 2020 11:21:26 +0000
From:   Jun Li <jun.li@....com>
To:     ChiYuan Huang <u0084500@...il.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



> -----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);
 }


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?

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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