linux-kernel - Re: [PATCH 1/4] usb: typec: tcpm: fix cc role at port reset

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Date:   Fri, 17 Mar 2023 05:47:10 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Frank Wang <frank.wang@...k-chips.com>
Cc:     gregkh@...uxfoundation.org, heiko@...ech.de,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, huangtao@...k-chips.com,
        william.wu@...k-chips.com, jianwei.zheng@...k-chips.com,
        yubing.zhang@...k-chips.com, wmc@...k-chips.com
Subject: Re: [PATCH 1/4] usb: typec: tcpm: fix cc role at port reset

On 3/17/23 04:24, Heikki Krogerus wrote:
> On Wed, Mar 15, 2023 at 10:55:20AM +0800, Frank Wang wrote:
>> Hi Heikki,
>>
>> On 2023/3/14 17:20, Heikki Krogerus wrote:
>>> On Mon, Mar 13, 2023 at 10:58:40AM +0800, Frank Wang wrote:
>>>> In the current implementation, the tcpm set CC1/CC2 role to open when
>>>> it do port reset would cause the VBUS removed by the Type-C partner.
>>>>
>>>> The Figure 4-20 in the TCPCI 2.0 specification show that the CC1/CC2
>>>> role should set to 01b (Rp) or 10b (Rd) at Power On or Reset stage
>>>> in DRP initialization and connection detection.
>>>>
>>>> So set CC1/CC2 to Rd to fix it.
>>>>
>>>> Signed-off-by: Frank Wang <frank.wang@...k-chips.com>
>>>> ---
>>>>    drivers/usb/typec/tcpm/tcpm.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
>>>> index a0d943d785800..66de02a56f512 100644
>>>> --- a/drivers/usb/typec/tcpm/tcpm.c
>>>> +++ b/drivers/usb/typec/tcpm/tcpm.c
>>>> @@ -4851,7 +4851,7 @@ static void run_state_machine(struct tcpm_port *port)
>>>>    		break;
>>>>    	case PORT_RESET:
>>>>    		tcpm_reset_port(port);
>>>> -		tcpm_set_cc(port, TYPEC_CC_OPEN);
>>>> +		tcpm_set_cc(port, TYPEC_CC_RD);
>>>>    		tcpm_set_state(port, PORT_RESET_WAIT_OFF,
>>>>    			       PD_T_ERROR_RECOVERY);
>>>>    		break;
>>> Will this work if the port is for example source only?
>>
>> Yeah, this only set at port reset stage and CC value will be set again
>> (Rd for Sink, Rp_* for Source) when start toggling.
> 
> Okay. Let's wait for comments from Guenter.
> 

Figure 4-20 is specifically for dual role ports. Also, start toggling would not
happen if the low level driver doesn't have a start_toggling callback. I think this
may require some tweaking based on the port type or, rather, tcpm_default_state().
Something like

	tcpm_set_cc(port, tcpm_default_state(port) == SNK_UNATTACHED ? TYPEC_CC_RD : tcpm_rp_cc(port));

Thanks,
Guenter