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Sender: Guenter Roeck <groeck7@gmail.com>
Subject: Re: [PATCH v1 1/3] usb: typec: tcpm: Add Callback to Usb
 Communication capable partner
To:     Badhri Jagan Sridharan <badhri@google.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Kyle Tso <kyletso@google.com>
Cc:     linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210201095309.39486-1-badhri@google.com>
From:   Guenter Roeck <linux@roeck-us.net>
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Message-ID: <ce97202a-5e94-6abe-d7f2-0e8c50b18eef@roeck-us.net>
Date:   Mon, 1 Feb 2021 06:59:37 -0800
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On 2/1/21 1:53 AM, Badhri Jagan Sridharan wrote:
> The USB Communications Capable bit indicates if port
> partner is capable of communication over the USB data lines
> (e.g. D+/- or SS Tx/Rx). Notify the status of the bit to low
> level drivers to perform chip specific operation.
> For instance, low level driver enables USB switches on D+/D-
> lines to set up data path when the bit is set.
> 
> Refactored from patch initially authored by
> Kyle Tso <kyletso@google.com>
> 
> Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 16 ++++++++++++++++
>  include/linux/usb/tcpm.h      |  5 +++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 0afd8ef692e8..96190b4d46a7 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -298,6 +298,7 @@ struct tcpm_port {
>  	struct usb_pd_identity partner_ident;
>  	struct typec_partner_desc partner_desc;
>  	struct typec_partner *partner;
> +	bool partner_usb_comm_capable;
>  
>  	enum typec_cc_status cc_req;
>  
> @@ -3429,6 +3430,16 @@ static void tcpm_unregister_altmodes(struct tcpm_port *port)
>  	memset(modep, 0, sizeof(*modep));
>  }
>  
> +static void tcpm_set_partner_usb_comm_capable(struct tcpm_port *port, bool capable)
> +{
> +	tcpm_log(port, "Setting usb_comm capable %s", capable ? "true" : "false");
> +
> +	if (port->tcpc->set_partner_usb_comm_capable)
> +		port->tcpc->set_partner_usb_comm_capable(port->tcpc, capable);
> +
> +	port->partner_usb_comm_capable = capable;
> +}
> +
>  static void tcpm_reset_port(struct tcpm_port *port)
>  {
>  	int ret;
> @@ -3445,6 +3456,7 @@ static void tcpm_reset_port(struct tcpm_port *port)
>  	port->attached = false;
>  	port->pd_capable = false;
>  	port->pps_data.supported = false;
> +	tcpm_set_partner_usb_comm_capable(port, false);
>  
>  	/*
>  	 * First Rx ID should be 0; set this to a sentinel of -1 so that
> @@ -3785,6 +3797,8 @@ static void run_state_machine(struct tcpm_port *port)
>  			}
>  		} else {
>  			tcpm_pd_send_control(port, PD_CTRL_ACCEPT);
> +			port->partner_usb_comm_capable = port->sink_request & RDO_USB_COMM;

That seems to be redundant since tcpm_set_partner_usb_comm_capable() is setting it again.

> +			tcpm_set_partner_usb_comm_capable(port, port->partner_usb_comm_capable);
>  			tcpm_set_state(port, SRC_TRANSITION_SUPPLY,
>  				       PD_T_SRC_TRANSITION);
>  		}
> @@ -4004,6 +4018,8 @@ static void run_state_machine(struct tcpm_port *port)
>  		break;
>  	case SNK_NEGOTIATE_CAPABILITIES:
>  		port->pd_capable = true;
> +		port->partner_usb_comm_capable = port->sink_request & RDO_USB_COMM;

Same here. But then I don't really see where this variable is actually used.
Am I missing something ?

Thanks,
Guenter

> +		tcpm_set_partner_usb_comm_capable(port, port->partner_usb_comm_capable);
>  		port->hard_reset_count = 0;
>  		ret = tcpm_pd_send_request(port);
>  		if (ret < 0) {
> diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
> index 3af99f85e8b9..42fcfbe10590 100644
> --- a/include/linux/usb/tcpm.h
> +++ b/include/linux/usb/tcpm.h
> @@ -108,6 +108,10 @@ enum tcpm_transmit_type {
>   *		is supported by TCPC, set this callback for TCPM to query
>   *		whether vbus is at VSAFE0V when needed.
>   *		Returns true when vbus is at VSAFE0V, false otherwise.
> + * @set_partner_usb_comm_capable:
> + *              Optional; The USB Communications Capable bit indicates if port
> + *              partner is capable of communication over the USB data lines
> + *              (e.g. D+/- or SS Tx/Rx). Called to notify the status of the bit.
>   */
>  struct tcpc_dev {
>  	struct fwnode_handle *fwnode;
> @@ -139,6 +143,7 @@ struct tcpc_dev {
>  	int (*set_auto_vbus_discharge_threshold)(struct tcpc_dev *dev, enum typec_pwr_opmode mode,
>  						 bool pps_active, u32 requested_vbus_voltage);
>  	bool (*is_vbus_vsafe0v)(struct tcpc_dev *dev);
> +	void (*set_partner_usb_comm_capable)(struct tcpc_dev *dev, bool enable);
>  };
>  
>  struct tcpm_port;
>