linux-kernel - Re: [PATCH] usb: typec: don't disable sink or source on initialization

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Message-ID: <0adff11c-4836-4035-39a7-1cd2ea3ff74d@roeck-us.net>
Date:   Fri, 7 Sep 2018 05:55:53 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        "Angus Ainslie (Purism)" <angus@...ea.ca>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: don't disable sink or source on
 initialization

On 09/07/2018 03:34 AM, Heikki Krogerus wrote:
> +Guenter
> 
> On Thu, Sep 06, 2018 at 01:26:44PM -0600, Angus Ainslie (Purism) wrote:
>> If the board is being powered by USB disabling the source and sink
>> can remove power from the board. Default to source and sink enabled.
>>

Seems to me that might violate the specification, and cause trouble for systems
where vbus has to be off initially. It may be better to provide this kind of
information as configuration parameter instead of imposing it on everyone.

Guenter

>> Signed-off-by: Angus Ainslie (Purism) <angus@...ea.ca>
>> ---
>>   drivers/usb/typec/tcpm.c | 8 +++++---
>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
>> index ca7bedb46f7f..a1b819cf31da 100644
>> --- a/drivers/usb/typec/tcpm.c
>> +++ b/drivers/usb/typec/tcpm.c
>> @@ -2462,9 +2462,11 @@ static int tcpm_init_vbus(struct tcpm_port *port)
>>   {
>>   	int ret;
>>   
>> -	ret = port->tcpc->set_vbus(port->tcpc, false, false);
>> -	port->vbus_source = false;
>> -	port->vbus_charge = false;
>> +	/* default to source and sink enabled in case USB is our only power
>> +	 * source */

I am personally in favor of standard multi-line comments.

>> +	ret = port->tcpc->set_vbus(port->tcpc, true, true);
>> +	port->vbus_source = true;
>> +	port->vbus_charge = true;
>>   	return ret;
>>   }
>