linux-kernel - Re: [PATCH 2/3] [PATCH v2 2/3] usb: typec: tcpm: Do not disconnect link for self powered devices

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Message-ID: <b9c66b15-7af3-a987-1299-dded17b5683e@roeck-us.net>
Date:   Sun, 30 Sep 2018 15:04:37 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Badhri Jagan Sridharan <badhri@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Andrzej Hajda <a.hajda@...sung.com>, Li Jun <jun.li@....com>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH 2/3] [PATCH v2 2/3] usb: typec: tcpm: Do not disconnect
 link for self powered devices

On 09/28/2018 04:47 PM, Badhri Jagan Sridharan wrote:
> During HARD_RESET the data link is disconnected.
> For self powered device, the spec is advising against doing that.
> 
>>>From USB_PD_R3_0
> 7.1.5 Response to Hard Resets
> Device operation during and after a Hard Reset is defined as follows:
> Self-powered devices Should Not disconnect from USB during a Hard Reset
> (see Section 9.1.2).
> Bus powered devices will disconnect from USB during a Hard Reset due to the
> loss of their power source.
> 
> Tackle this by letting TCPM know whether the device is self or bus powered.
> 
> This overcomes unnecessary port disconnections from hard reset.
> Also, speeds up the enumeration time when connected to Type-A ports.
> 
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---------
> Version history:
> 
> V2:
> Based on feedback from heikki.krogerus@...ux.intel.com
> - self_powered added to the struct tcpm_port which is populated from
>    a. "connector" node of the device tree in tcpm_fw_get_caps()
>    b. "self_powered" node of the tcpc_config in tcpm_copy_caps
> 
> Based on feedbase from linux@...ck-us.net
> - Code was refactored
> - SRC_HARD_RESET_VBUS_OFF sets the link state to false based
>    on self_powered flag
> 
> V1 located here:
> https://lkml.org/lkml/2018/9/13/94
> ---
>   drivers/usb/typec/tcpm.c | 12 ++++++++++--
>   include/linux/usb/tcpm.h |  1 +
>   2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
> index 4f1f4215f3d6e..c3ac0e46106b4 100644
> --- a/drivers/usb/typec/tcpm.c
> +++ b/drivers/usb/typec/tcpm.c
> @@ -317,6 +317,9 @@ struct tcpm_port {
>   	/* Deadline in jiffies to exit src_try_wait state */
>   	unsigned long max_wait;
>   
> +	/* port belongs to a self powered device */
> +	bool self_powered;
> +
>   #ifdef CONFIG_DEBUG_FS
>   	struct dentry *dentry;
>   	struct mutex logbuffer_lock;	/* log buffer access lock */
> @@ -3257,7 +3260,8 @@ static void run_state_machine(struct tcpm_port *port)
>   	case SRC_HARD_RESET_VBUS_OFF:
>   		tcpm_set_vconn(port, true);
>   		tcpm_set_vbus(port, false);
> -		tcpm_set_roles(port, false, TYPEC_SOURCE, TYPEC_HOST);
> +		tcpm_set_roles(port, port->self_powered, TYPEC_SOURCE,
> +			       TYPEC_HOST);
>   		tcpm_set_state(port, SRC_HARD_RESET_VBUS_ON, PD_T_SRC_RECOVER);
>   		break;
>   	case SRC_HARD_RESET_VBUS_ON:
> @@ -3270,7 +3274,8 @@ static void run_state_machine(struct tcpm_port *port)
>   		memset(&port->pps_data, 0, sizeof(port->pps_data));
>   		tcpm_set_vconn(port, false);
>   		tcpm_set_charge(port, false);
> -		tcpm_set_roles(port, false, TYPEC_SINK, TYPEC_DEVICE);
> +		tcpm_set_roles(port, port->self_powered, TYPEC_SINK,
> +			       TYPEC_DEVICE);
>   		/*
>   		 * VBUS may or may not toggle, depending on the adapter.
>   		 * If it doesn't toggle, transition to SNK_HARD_RESET_SINK_ON
> @@ -4409,6 +4414,8 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
>   		return -EINVAL;
>   	port->operating_snk_mw = mw / 1000;
>   
> +	port->self_powered = fwnode_property_read_bool(fwnode, "self-powered");
> +
>   	return 0;
>   }
>   
> @@ -4717,6 +4724,7 @@ static int tcpm_copy_caps(struct tcpm_port *port,
>   	port->typec_caps.prefer_role = tcfg->default_role;
>   	port->typec_caps.type = tcfg->type;
>   	port->typec_caps.data = tcfg->data;
> +	port->self_powered = port->tcpc->config->self_powered;
>   
>   	return 0;
>   }
> diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
> index 7e7fbfb84e8e3..50c74a77db55c 100644
> --- a/include/linux/usb/tcpm.h
> +++ b/include/linux/usb/tcpm.h
> @@ -89,6 +89,7 @@ struct tcpc_config {
>   	enum typec_port_data data;
>   	enum typec_role default_role;
>   	bool try_role_hw;	/* try.{src,snk} implemented in hardware */
> +	bool self_powered;	/* port belongs to a self powered device */
>   
>   	const struct typec_altmode_desc *alt_modes;
>   };
>