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 <hdego...@redhat.com> --- 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 --- drivers/usb/typec/tcpm/tcpm.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c index f1c39a3c7534..3f8df845d1a5 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_CAP_LOWER_PD_REVISION), \ S(SRC_NEGOTIATE_CAPABILITIES), \ S(SRC_TRANSITION_SUPPLY), \ S(SRC_READY), \ @@ -2792,6 +2793,29 @@ static inline enum tcpm_state hard_reset_state(struct tcpm_port *port) return SNK_UNATTACHED; } +/* + * 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 function is used by the SRC_SEND_CAPABILITIES state in + * run_state_machine() to work around this. + * + * After PD_N_HARD_RESET_COUNT hard-reset attempts this function selects + * SRC_SEND_CAP_LOWER_PD_REVISION as state to set after the next timeout, + * this state will fallback to a lower PD revision and then try sending the + * src-capabilities again. + */ +static inline enum tcpm_state src_send_cap_timeout_state(struct tcpm_port *port) +{ + if (port->hard_reset_count < PD_N_HARD_RESET_COUNT) + return HARD_RESET_SEND; + if (port->negotiated_rev > PD_REV20) + return SRC_SEND_CAP_LOWER_PD_REVISION; + return hard_reset_state(port); +} + static inline enum tcpm_state unattached_state(struct tcpm_port *port) { if (port->port_type == TYPEC_PORT_DRP) { @@ -2966,10 +2990,18 @@ 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_cap_timeout_state(port), PD_T_SEND_SOURCE_CAP); } break; + case SRC_SEND_CAP_LOWER_PD_REVISION: + if (WARN_ON(port->negotiated_rev <= PD_REV20)) + break; + port->negotiated_rev--; + port->hard_reset_count = 0; + tcpm_set_state(port, SRC_SEND_CAPABILITIES, 0); + break; case SRC_NEGOTIATE_CAPABILITIES: ret = tcpm_pd_check_request(port); if (ret < 0) { -- 2.20.1
