On Fri, Mar 15, 2019 at 03:42:19PM +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@xxxxxxxxxx> > --- > 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; I really dislike the WARN_ON here. A bad remote can potentially trigger this, which on systems with crash on warning enabled can result in a reboot. Just revert to the original behavior here, and maybe add a tcpm log message. Guenter > + 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 >
