On Wed, Jun 16, 2021 at 05:01:02PM +0800, Kyle Tso wrote:
> If the voltage is being decreased in power negotiation, the Source will
> set the power supply to operate at the new voltage level before sending
> PS_RDY. Relax the threshold before sending Request Message so that it
> will not race with Source which begins to adjust the voltage right after
> it sends Accept Message (PPS) or tSrcTransition (25~35ms) after it sends
> Accept Message (non-PPS).
>
> The real threshold will be set after Sink receives PS_RDY Message.
>
> Fixes: f321a02caebd ("usb: typec: tcpm: Implement enabling Auto Discharge disconnect support")
> Cc: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
> Signed-off-by: Kyle Tso <kyletso@xxxxxxxxxx>
Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> Changes in v3:
> - move the timing of setting threshold for Fixed RDO as I did for PPS in
> v2, i.e. move it to tcpm_pd_send_request.
> - add Cc: tag for Badhri
> - update the commit message for the above changes
>
> Changes in v2:
> - move the timing of setting threshold up to "before sending Request"
> for PPS power negotiation so that it won't race with the Source.
> - PPS: if it fails to send the Request, fallback to previous threshold
> - PPS: if the Source doesn't respond Accept, fallback to previous
> threshold
> - update the commit message for above changes
>
> drivers/usb/typec/tcpm/tcpm.c | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 197556038ba4..b1d310ab84c4 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -2604,6 +2604,11 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> } else {
> next_state = SNK_WAIT_CAPABILITIES;
> }
> +
> + /* Threshold was relaxed before sending Request. Restore it back. */
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> + port->pps_data.active,
> + port->supply_voltage);
> tcpm_set_state(port, next_state, 0);
> break;
> case SNK_NEGOTIATE_PPS_CAPABILITIES:
> @@ -2617,6 +2622,11 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> port->send_discover)
> port->vdm_sm_running = true;
>
> + /* Threshold was relaxed before sending Request. Restore it back. */
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> + port->pps_data.active,
> + port->supply_voltage);
> +
> tcpm_set_state(port, SNK_READY, 0);
> break;
> case DR_SWAP_SEND:
> @@ -3336,6 +3346,12 @@ static int tcpm_pd_send_request(struct tcpm_port *port)
> if (ret < 0)
> return ret;
>
> + /*
> + * Relax the threshold as voltage will be adjusted after Accept Message plus tSrcTransition.
> + * It is safer to modify the threshold here.
> + */
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, 0);
> +
> memset(&msg, 0, sizeof(msg));
> msg.header = PD_HEADER_LE(PD_DATA_REQUEST,
> port->pwr_role,
> @@ -3433,6 +3449,9 @@ static int tcpm_pd_send_pps_request(struct tcpm_port *port)
> if (ret < 0)
> return ret;
>
> + /* Relax the threshold as voltage will be adjusted right after Accept Message. */
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, 0);
> +
> memset(&msg, 0, sizeof(msg));
> msg.header = PD_HEADER_LE(PD_DATA_REQUEST,
> port->pwr_role,
> @@ -4196,6 +4215,10 @@ static void run_state_machine(struct tcpm_port *port)
> port->hard_reset_count = 0;
> ret = tcpm_pd_send_request(port);
> if (ret < 0) {
> + /* Restore back to the original state */
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> + port->pps_data.active,
> + port->supply_voltage);
> /* Let the Source send capabilities again. */
> tcpm_set_state(port, SNK_WAIT_CAPABILITIES, 0);
> } else {
> @@ -4206,6 +4229,10 @@ static void run_state_machine(struct tcpm_port *port)
> case SNK_NEGOTIATE_PPS_CAPABILITIES:
> ret = tcpm_pd_send_pps_request(port);
> if (ret < 0) {
> + /* Restore back to the original state */
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> + port->pps_data.active,
> + port->supply_voltage);
> port->pps_status = ret;
> /*
> * If this was called due to updates to sink
> --
> 2.32.0.272.g935e593368-goog
--
heikki
