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Sender: Guenter Roeck <groeck7@gmail.com>
Subject: Re: [PATCH 1/2] usb: typec: tcpm: Properly interrupt VDM AMS
To:     Kyle Tso <kyletso@google.com>, heikki.krogerus@linux.intel.com,
        gregkh@linuxfoundation.org
Cc:     badhri@google.com, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20210521130121.1470334-1-kyletso@google.com>
 <20210521130121.1470334-2-kyletso@google.com>
From:   Guenter Roeck <linux@roeck-us.net>
Message-ID: <6872a037-c036-fd1c-608a-c33e4ef22923@roeck-us.net>
Date:   Fri, 21 May 2021 07:48:30 -0700
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On 5/21/21 6:01 AM, Kyle Tso wrote:
> When a VDM AMS is interrupted by Messages other than VDM, the AMS needs
> to be finished properly. Also start a VDM AMS if receiving SVDM Commands
> from the port partner to complement the functionality of tcpm_vdm_ams().
> 
> Fixes: 0908c5aca31e ("usb: typec: tcpm: AMS and Collision Avoidance")
> Signed-off-by: Kyle Tso <kyletso@google.com>

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

> ---
>   drivers/usb/typec/tcpm/tcpm.c | 30 ++++++++++++++++++++++++++++++
>   1 file changed, 30 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 64133e586c64..deb8a9d01f73 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -1550,6 +1550,8 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
>   			if (PD_VDO_SVDM_VER(p[0]) < svdm_version)
>   				typec_partner_set_svdm_version(port->partner,
>   							       PD_VDO_SVDM_VER(p[0]));
> +
> +			tcpm_ams_start(port, DISCOVER_IDENTITY);
>   			/* 6.4.4.3.1: Only respond as UFP (device) */
>   			if (port->data_role == TYPEC_DEVICE &&
>   			    port->nr_snk_vdo) {
> @@ -1568,14 +1570,19 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
>   			}
>   			break;
>   		case CMD_DISCOVER_SVID:
> +			tcpm_ams_start(port, DISCOVER_SVIDS);
>   			break;
>   		case CMD_DISCOVER_MODES:
> +			tcpm_ams_start(port, DISCOVER_MODES);
>   			break;
>   		case CMD_ENTER_MODE:
> +			tcpm_ams_start(port, DFP_TO_UFP_ENTER_MODE);
>   			break;
>   		case CMD_EXIT_MODE:
> +			tcpm_ams_start(port, DFP_TO_UFP_EXIT_MODE);
>   			break;
>   		case CMD_ATTENTION:
> +			tcpm_ams_start(port, ATTENTION);
>   			/* Attention command does not have response */
>   			*adev_action = ADEV_ATTENTION;
>   			return 0;
> @@ -2287,6 +2294,12 @@ static void tcpm_pd_data_request(struct tcpm_port *port,
>   	bool frs_enable;
>   	int ret;
>   
> +	if (tcpm_vdm_ams(port) && type != PD_DATA_VENDOR_DEF) {
> +		port->vdm_state == VDM_STATE_ERR_BUSY;
> +		tcpm_ams_finish(port);
> +		mod_vdm_delayed_work(port, 0);
> +	}
> +
>   	switch (type) {
>   	case PD_DATA_SOURCE_CAP:
>   		for (i = 0; i < cnt; i++)
> @@ -2459,6 +2472,16 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
>   	enum pd_ctrl_msg_type type = pd_header_type_le(msg->header);
>   	enum tcpm_state next_state;
>   
> +	/*
> +	 * Stop VDM state machine if interrupted by other Messages while NOT_SUPP is allowed in
> +	 * VDM AMS if waiting for VDM responses and will be handled later.
> +	 */
> +	if (tcpm_vdm_ams(port) && type != PD_CTRL_NOT_SUPP && type != PD_CTRL_GOOD_CRC) {
> +		port->vdm_state = VDM_STATE_ERR_BUSY;
> +		tcpm_ams_finish(port);
> +		mod_vdm_delayed_work(port, 0);
> +	}
> +
>   	switch (type) {
>   	case PD_CTRL_GOOD_CRC:
>   	case PD_CTRL_PING:
> @@ -2717,6 +2740,13 @@ static void tcpm_pd_ext_msg_request(struct tcpm_port *port,
>   	enum pd_ext_msg_type type = pd_header_type_le(msg->header);
>   	unsigned int data_size = pd_ext_header_data_size_le(msg->ext_msg.header);
>   
> +	/* stopping VDM state machine if interrupted by other Messages */
> +	if (tcpm_vdm_ams(port)) {
> +		port->vdm_state = VDM_STATE_ERR_BUSY;
> +		tcpm_ams_finish(port);
> +		mod_vdm_delayed_work(port, 0);
> +	}
> +
>   	if (!(msg->ext_msg.header & PD_EXT_HDR_CHUNKED)) {
>   		tcpm_pd_handle_msg(port, PD_MSG_CTRL_NOT_SUPP, NONE_AMS);
>   		tcpm_log(port, "Unchunked extended messages unsupported");
>