On 9/3/20 9:21 AM, ChiYuan Huang wrote: > Guenter Roeck <linux@xxxxxxxxxxxx> 於 2020年9月3日 週四 上午12:57寫道： >> >> On Wed, Sep 02, 2020 at 11:35:33PM +0800, cy_huang wrote: >>> From: ChiYuan Huang <cy_huang@xxxxxxxxxxx> >>> >>> Fix: If vbus event is before cc_event trigger, hard_reset_count >>> won't bt reset for some case. >>> >>> Signed-off-by: ChiYuan Huang <cy_huang@xxxxxxxxxxx> >>> --- >>> Below's the flow. >>> >>> _tcpm_pd_vbus_off() -> run_state_machine to change state to SNK_UNATTACHED >>> call tcpm_snk_detach() -> tcpm_snk_detach() -> tcpm_detach() >>> tcpm_port_is_disconnected() will be called. >>> But port->attached is still true and port->cc1=open and port->cc2=open >>> >>> It cause tcpm_port_is_disconnected return false, then hard_reset_count won't be reset. >>> After that, tcpm_reset_port() is called. >>> port->attached become false. >>> >>> After that, cc now trigger cc_change event, the hard_reset_count will be kept. >>> Even tcpm_detach will be called, due to port->attached is false, tcpm_detach() >>> will directly return. >>> >>> CC_EVENT will only trigger drp toggling again. >>> --- >>> drivers/usb/typec/tcpm/tcpm.c | 3 +-- >>> 1 file changed, 1 insertion(+), 2 deletions(-) >>> >>> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c >>> index a48e3f90..5c73e1d 100644 >>> --- a/drivers/usb/typec/tcpm/tcpm.c >>> +++ b/drivers/usb/typec/tcpm/tcpm.c >>> @@ -2797,8 +2797,7 @@ 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; >>> + port->hard_reset_count = 0; >>> >> >> Doesn't that mean that the state machine will never enter >> error recovery ? >> > I think it does't affect the error recovery. > All error recovery seems to check pd_capable flag. > >>From my below case, it's A to C cable only. There is no USBPD contract > will be estabilished. > > This case occurred following by the below test condition > Cable -> A to C (default Rp bind to vbus) connected to PC. > 1. first time plugged in the cable with PC > It will make HARD_RESET_COUNT to be equal 2 > 2. And then plug out. At that time HARD_RESET_COUNT is till 2. > 3. next time plugged in again. > Due to hard_reset_count is still 2 , after wait_cap_timeout, the state > eventually changed to SNK_READY. > But during the state transition, no hard_reset be sent. > > Defined in the USBPD policy engine, typec transition to USBPD, all > variables must be reset included hard_reset_count. > So it expected SNK must send hard_reset again. > > The original code defined hard_reset_count must be reset only when > tcpm_port_is_disconnected. > > It doesn't make sense that it only occurred in some scenario. > If tcpm_detach is called, hard_reset count must be reset also. > If a hard reset fails, the state machine may cycle through states HARD_RESET_SEND, HARD_RESET_START, SRC_HARD_RESET_VBUS_OFF, SRC_HARD_RESET_VBUS_ON back to SRC_UNATTACHED. In this state, tcpm_src_detach() and with it tcpm_detach() is called. The hard reset counter is incremented in HARD_RESET_SEND. If tcpm_detach() resets the counter, the state machine will keep cycling through hard resets without ever entering the error recovery state. I am not entirely sure where the counter should be reset, but tcpm_detach() seems to be the wrong place. Guenter >> Guenter >> >>> tcpm_reset_port(port); >>> } >>> -- >>> 2.7.4 >>>
