Re: [PATCH regression fix] usb: typec: tcpm: Fix VDMs sometimes not being forwarded to alt-mode drivers

[Guenter Roeck <linux@roeck-us.net>]

On 8/16/21 8:46 AM, Hans de Goede wrote:
> Commit a20dcf53ea98 ("usb: typec: tcpm: Respond Not_Supported if no
> snk_vdo"), stops tcpm_pd_data_request() calling tcpm_handle_vdm_request()
> when port->nr_snk_vdo is not set. But the VDM might be intended for an
> altmode-driver, in which case nr_snk_vdo does not matter.
> 
> This change breaks the forwarding of connector hotplug (HPD) events
> for displayport altmode on devices which don't set nr_snk_vdo.
> 
> tcpm_pd_data_request() is the only caller of tcpm_handle_vdm_request(),
> so we can move the nr_snk_vdo check to inside it, at which point we
> have already looked up the altmode device so we can check for this too.
> 
> Doing this check here also ensures that vdm_state gets set to
> VDM_STATE_DONE if it was VDM_STATE_BUSY, even if we end up with
> responding with PD_MSG_CTRL_NOT_SUPP later.
> 
> Note that tcpm_handle_vdm_request() was already sending
> PD_MSG_CTRL_NOT_SUPP in some circumstances, after moving the nr_snk_vdo
> check the same error-path is now taken when that check fails. So that
> we have only one error-path for this and not two. Replace the
> tcpm_queue_message(PD_MSG_CTRL_NOT_SUPP) used by the existing error-path
> with the more robust tcpm_pd_handle_msg() from the (now removed) second
> error-path.
> 
> Cc: Kyle Tso <kyletso@google.com>
> Fixes: a20dcf53ea98 ("usb: typec: tcpm: Respond Not_Supported if no snk_vdo")
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

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

> ---
>   drivers/usb/typec/tcpm/tcpm.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index b9bb63d749ec..f4079b5cb26d 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -1737,6 +1737,10 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
>   	return rlen;
>   }
>   
> +static void tcpm_pd_handle_msg(struct tcpm_port *port,
> +			       enum pd_msg_request message,
> +			       enum tcpm_ams ams);
> +
>   static void tcpm_handle_vdm_request(struct tcpm_port *port,
>   				    const __le32 *payload, int cnt)
>   {
> @@ -1764,11 +1768,11 @@ static void tcpm_handle_vdm_request(struct tcpm_port *port,
>   		port->vdm_state = VDM_STATE_DONE;
>   	}
>   
> -	if (PD_VDO_SVDM(p[0])) {
> +	if (PD_VDO_SVDM(p[0]) && (adev || tcpm_vdm_ams(port) || port->nr_snk_vdo)) {
>   		rlen = tcpm_pd_svdm(port, adev, p, cnt, response, &adev_action);
>   	} else {
>   		if (port->negotiated_rev >= PD_REV30)
> -			tcpm_queue_message(port, PD_MSG_CTRL_NOT_SUPP);
> +			tcpm_pd_handle_msg(port, PD_MSG_CTRL_NOT_SUPP, NONE_AMS);
>   	}
>   
>   	/*
> @@ -2471,10 +2475,7 @@ static void tcpm_pd_data_request(struct tcpm_port *port,
>   					   NONE_AMS);
>   		break;
>   	case PD_DATA_VENDOR_DEF:
> -		if (tcpm_vdm_ams(port) || port->nr_snk_vdo)
> -			tcpm_handle_vdm_request(port, msg->payload, cnt);
> -		else if (port->negotiated_rev > PD_REV20)
> -			tcpm_pd_handle_msg(port, PD_MSG_CTRL_NOT_SUPP, NONE_AMS);
> +		tcpm_handle_vdm_request(port, msg->payload, cnt);
>   		break;
>   	case PD_DATA_BIST:
>   		port->bist_request = le32_to_cpu(msg->payload[0]);
>