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From: Guenter Roeck <linux@roeck-us.net>
To: Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Icenowy Zheng <icenowy@aosc.io>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: typec: tcpm: always rediscover when swapping DR
Date: Tue, 17 Aug 2021 08:13:28 -0700	[thread overview]
Message-ID: <58034df4-f18c-ab3e-1fcc-dc85fc35320f@roeck-us.net> (raw)
In-Reply-To: <YRuDG78N2mB5w37p@kuha.fi.intel.com>

On 8/17/21 2:36 AM, Heikki Krogerus wrote:
> 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?
> 
> thanks,
> 

Additional question: There are two patches pending related to DR_SWAP
and discovery. Are they both needed, or do they both solve the same
problem ?

Thanks,
Guenter

  parent reply	other threads:[~2021-08-17 15:13 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-13  4:31 Icenowy Zheng
2021-08-17  9:36 ` Heikki Krogerus
2021-08-17  9:41   ` Icenowy Zheng
2021-08-17 11:00     ` Heikki Krogerus
2021-08-18 13:56       ` Greg Kroah-Hartman
2021-08-18 14:02         ` Icenowy Zheng
2021-08-18 14:40           ` Greg Kroah-Hartman
2021-08-18 16:13             ` Kyle Tso
2021-08-18 16:17               ` Icenowy Zheng
2021-08-18 16:24               ` Icenowy Zheng
2021-08-17 15:13   ` Guenter Roeck [this message]
2021-08-18  8:02     ` Kyle Tso
2021-08-18  8:16       ` Kyle Tso
2021-08-18  9:20       ` Icenowy Zheng
2021-08-18  9:27       ` Icenowy Zheng
2021-08-18 10:47         ` Kyle Tso

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