Re: [PATCH 4/4] usb: typec: tcpm: fix source caps may lost after soft reset

[Frank Wang <frank.wang@xxxxxxxxxxxxxx>]

Hi Guenter,

On 2023/3/17 20:58, Guenter Roeck wrote:
> On 3/12/23 19:58, Frank Wang wrote:
> > Invoke set_pd_rx() may flush the RX FIFO of PD controller, so do
> > set_pd_rx() before sending Soft Reset in case Source caps may be flushed
> > at debounce time between SOFT_RESET_SEND and SNK_WAIT_CAPABILITIES 
> > state.
>
> Isn't that a problem of the fusb302 driver that it flushes its buffers
> unconditionally when its set_pd_rx() callback is called ?
>
> Guenter

The story goes like this,  the fusb302 notified SOFT_RESET completion to 
TCPM and began to receive the Source Caps automatically,
TCPM got completion from fusb302 and changed state to 
SNK_WAIT_CAPABILITIES and invoked set_pd_rx() callback. However, the
fusb302 or TCPM's worker may be not scheduled in time, set_pd_rx() would 
be performed after the Source Caps packets had received
into fusb302's FIFO, even after the GoodCRC (Source Caps) had be replied.

So make forward set_pd_rx() process before PD_CTRL_SOFT_RESET sent at 
SOFT_RESET_SEND state can cleanup the context in our side
and ensure the right PD commucation. I am not sure whether it is sensible?

BR.
Frank

> > Without this patch, in PD charger stress test, the FUSB302 driver may
> > occur the following exceptions in power negotiation stage.
> >
> > [ ...]
> > [ 4.512252] fusb302_irq_intn
> > [ 4.512260] AMS SOFT_RESET_AMS finished
> > [ 4.512269] state change SOFT_RESET_SEND ->SNK_WAIT_CAPABILITIES 
> > [rev3 NONE_AMS]
> > [ 4.514511] pd := on
> > [ 4.514516] pending state change SNK_WAIT_CAPABILITIES 
> > ->HARD_RESET_SEND @ 310 ms [rev3 NONE_AMS]
> > [ 4.515428] IRQ: 0x51, a: 0x00, b: 0x01, status0: 0x93
> > [ 4.515431] IRQ: BC_LVL, handler pending
> > [ 4.515435] IRQ: PD sent good CRC
> > [ 4.516434] PD message header: 0
> > [ 4.516437] PD message len: 0
> > [ 4.516444] PD RX, header: 0x0 [1]
> >
> > Signed-off-by: Frank Wang <frank.wang@xxxxxxxxxxxxxx>
> > ---
> >   drivers/usb/typec/tcpm/tcpm.c | 11 +++++++----
> >   1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c 
> > b/drivers/usb/typec/tcpm/tcpm.c
> > index 9e583060e64fc..ba6bf71838eed 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -4321,10 +4321,12 @@ static void run_state_machine(struct 
> > tcpm_port *port)
> >           tcpm_set_state(port, unattached_state(port), 0);
> >           break;
> >       case SNK_WAIT_CAPABILITIES:
> > -        ret = port->tcpc->set_pd_rx(port->tcpc, true);
> > -        if (ret < 0) {
> > -            tcpm_set_state(port, SNK_READY, 0);
> > -            break;
> > +        if (port->prev_state != SOFT_RESET_SEND) {
> > +            ret = port->tcpc->set_pd_rx(port->tcpc, true);
> > +            if (ret < 0) {
> > +                tcpm_set_state(port, SNK_READY, 0);
> > +                break;
> > +            }
> >           }
> >           /*
> >            * If VBUS has never been low, and we time out waiting
> > @@ -4603,6 +4605,7 @@ static void run_state_machine(struct tcpm_port 
> > *port)
> >       case SOFT_RESET_SEND:
> >           port->message_id = 0;
> >           port->rx_msgid = -1;
> > +        port->tcpc->set_pd_rx(port->tcpc, true);
> >           if (tcpm_pd_send_control(port, PD_CTRL_SOFT_RESET))
> >               tcpm_set_state_cond(port, hard_reset_state(port), 0);
> >           else