[v2] usb: typec: tcpm: Try PD-2.0 if sink does not respond to 3.0 source-caps

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Sat, Mar 16, 2019 at 04:57:12PM +0100, Hans de Goede wrote:
> PD 2.0 sinks are supposed to accept src-capabilities with a 3.0 header and
> simply ignore any src PDOs which the sink does not understand such as PPS
> but some 2.0 sinks instead ignore the entire PD_DATA_SOURCE_CAP message,
> causing contract negotiation to fail.
> 
> This commit fixes such sinks not working by re-trying the contract
> negotiation with PD-2.0 source-caps messages if we don't have a contract
> after PD_N_HARD_RESET_COUNT hard-reset attempts.
> 
> The problem fixed by this commit was noticed with a Type-C to VGA dongle.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

Also applied to my typec-next branch:
https://github.com/krohei/linux/commit/35e8c23e398ad03e7d9268a11a0408f8642da6d0

> ---
> The Type-C to VGA dongle on which this encountered looks like this one:
> https://www.aliexpress.com/item/Male-USB-3-1-Type-C-USB-C-to-Female-VGA-Adapter-Cable-10Gbps-for-New/32898274476.html
> ---
> Changes in v2:
> -Refactor the patch to avoid a check vs use race wrt negotiated_rev
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index f1c39a3c7534..d34e945e5d09 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -37,6 +37,7 @@
>  	S(SRC_ATTACHED),			\
>  	S(SRC_STARTUP),				\
>  	S(SRC_SEND_CAPABILITIES),		\
> +	S(SRC_SEND_CAPABILITIES_TIMEOUT),	\
>  	S(SRC_NEGOTIATE_CAPABILITIES),		\
>  	S(SRC_TRANSITION_SUPPLY),		\
>  	S(SRC_READY),				\
> @@ -2966,10 +2967,34 @@ static void run_state_machine(struct tcpm_port *port)
>  			/* port->hard_reset_count = 0; */
>  			port->caps_count = 0;
>  			port->pd_capable = true;
> -			tcpm_set_state_cond(port, hard_reset_state(port),
> +			tcpm_set_state_cond(port, SRC_SEND_CAPABILITIES_TIMEOUT,
>  					    PD_T_SEND_SOURCE_CAP);
>  		}
>  		break;
> +	case SRC_SEND_CAPABILITIES_TIMEOUT:
> +		/*
> +		 * Error recovery for a PD_DATA_SOURCE_CAP reply timeout.
> +		 *
> +		 * PD 2.0 sinks are supposed to accept src-capabilities with a
> +		 * 3.0 header and simply ignore any src PDOs which the sink does
> +		 * not understand such as PPS but some 2.0 sinks instead ignore
> +		 * the entire PD_DATA_SOURCE_CAP message, causing contract
> +		 * negotiation to fail.
> +		 *
> +		 * After PD_N_HARD_RESET_COUNT hard-reset attempts, we try
> +		 * sending src-capabilities with a lower PD revision to
> +		 * make these broken sinks work.
> +		 */
> +		if (port->hard_reset_count < PD_N_HARD_RESET_COUNT) {
> +			tcpm_set_state(port, HARD_RESET_SEND, 0);
> +		} else if (port->negotiated_rev > PD_REV20) {
> +			port->negotiated_rev--;
> +			port->hard_reset_count = 0;
> +			tcpm_set_state(port, SRC_SEND_CAPABILITIES, 0);
> +		} else {
> +			tcpm_set_state(port, hard_reset_state(port), 0);
> +		}
> +		break;
>  	case SRC_NEGOTIATE_CAPABILITIES:
>  		ret = tcpm_pd_check_request(port);
>  		if (ret < 0) {
> -- 
> 2.20.1

thanks,