Re: [PATCH] usb: typec: tcpm: always rediscover when swapping DR

[Icenowy Zheng <icenowy@aosc.io>]

于 2021年8月17日 GMT+08:00 下午5:36:27, Heikki Krogerus <heikki.krogerus@linux.intel.com> 写到:
>On Fri, Aug 13, 2021 at 12:31:31PM +0800, Icenowy Zheng wrote:
>> Currently, TCPM code omits discover when swapping to gadget, and assume
>> that no altmodes are available when swapping from gadget. However, we do
>> send discover when we get attached as gadget -- this leads to modes to be
>> discovered twice when attached as gadget and then swap to host.
>> 
>> Always re-send discover when swapping DR, regardless of what change is
>> being made; and because of this, the assumption that no altmodes are
>> registered with gadget role is broken, and altmodes de-registeration is
>> always needed now.
>> 
>> Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
>> ---
>>  drivers/usb/typec/tcpm/tcpm.c | 9 ++++-----
>>  1 file changed, 4 insertions(+), 5 deletions(-)
>> 
>> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
>> index b9bb63d749ec..ab6d0d51ee1c 100644
>> --- a/drivers/usb/typec/tcpm/tcpm.c
>> +++ b/drivers/usb/typec/tcpm/tcpm.c
>> @@ -4495,15 +4495,14 @@ static void run_state_machine(struct tcpm_port *port)
>>  		tcpm_set_state(port, ready_state(port), 0);
>>  		break;
>>  	case DR_SWAP_CHANGE_DR:
>> -		if (port->data_role == TYPEC_HOST) {
>> -			tcpm_unregister_altmodes(port);
>> +		tcpm_unregister_altmodes(port);
>> +		if (port->data_role == TYPEC_HOST)
>>  			tcpm_set_roles(port, true, port->pwr_role,
>>  				       TYPEC_DEVICE);
>> -		} else {
>> +		else
>>  			tcpm_set_roles(port, true, port->pwr_role,
>>  				       TYPEC_HOST);
>> -			port->send_discover = true;
>> -		}
>> +		port->send_discover = true;
>>  		tcpm_ams_finish(port);
>>  		tcpm_set_state(port, ready_state(port), 0);
>>  		break;
>
>Why is it necessary to do discovery with data role swap in general?

I think it could be possible for devices to expose different altmode
with different role.

>
>thanks,
>