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

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Message-ID: <879d18af-e3a9-e953-1b3a-99965f74f63e@rock-chips.com>
Date:   Mon, 20 Mar 2023 10:28:55 +0800
From:   Frank Wang <frank.wang@...k-chips.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.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

Hi Guenter,

On 2023/3/17 20:47, Guenter Roeck wrote:
> 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));

To amend likes above make sense, I shall fix it later.


BR.
Frank

>
> Thanks,
> Guenter
>