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SubjectRe: [PATCH v1 3/4] usb: typec: tcpm: Move TCPC to APPLY_RC state during PR_SWAP
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On 5/14/21 10:26 PM, Badhri Jagan Sridharan wrote:
> When vbus auto discharge is enabled, TCPCI based TCPC transitions
> into Attached.SNK/Attached.SRC state. During PR_SWAP, TCPCI based
> TCPC would disconnect when partner changes power roles. TCPC has
> to be moved APPLY RC state during PR_SWAP. This is done by
> ROLE_CONTROL.CC1 != ROLE_CONTROL.CC2 and
> POWER_CONTROL.AutodischargeDisconnect is 0. Once the swap sequence
> is done, AutoDischargeDisconnect is re-enabled.
>
> Fixes: f321a02caebd ("usb: typec: tcpm: Implement enabling Auto Discharge disconnect support")
> Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
> ---
> drivers/usb/typec/tcpm/tcpm.c | 16 ++++++++++++++++
> include/linux/usb/tcpm.h | 4 ++++
> 2 files changed, 20 insertions(+)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index b475d9b9d38d..5bac4978efb3 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -786,6 +786,19 @@ static int tcpm_enable_auto_vbus_discharge(struct tcpm_port *port, bool enable)
> return ret;
> }
>
> +static void tcpm_apply_rc(struct tcpm_port *port)
> +{
> + /*
> + * TCPCI: Move to APPLY_RC state to prevent disconnect during PR_SWAP
> + * when Vbus auto discharge on disconnect is enabled.
> + */
> + if (port->tcpc->enable_auto_vbus_discharge) {
> + tcpm_log(port, "Apply_RC");
> + port->tcpc->apply_rc(port->tcpc, port->cc_req, port->polarity);

This is called unconditionally. I think you'll need an additional
&& port->tcpc->apply_rc
in the if statement above.

> + tcpm_enable_auto_vbus_discharge(port, false);
> + }
> +}
> +
> /*
> * Determine RP value to set based on maximum current supported
> * by a port if configured as source.
> @@ -4428,6 +4441,7 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_set_state(port, ready_state(port), 0);
> break;
> case PR_SWAP_START:
> + tcpm_apply_rc(port);
> if (port->pwr_role == TYPEC_SOURCE)
> tcpm_set_state(port, PR_SWAP_SRC_SNK_TRANSITION_OFF,
> PD_T_SRC_TRANSITION);
> @@ -4467,6 +4481,7 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_set_state(port, ERROR_RECOVERY, PD_T_PS_SOURCE_ON_PRS);
> break;
> case PR_SWAP_SRC_SNK_SINK_ON:
> + tcpm_enable_auto_vbus_discharge(port, true);
> /* Set the vbus disconnect threshold for implicit contract */
> tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, VSAFE5V);
> tcpm_set_state(port, SNK_STARTUP, 0);
> @@ -4483,6 +4498,7 @@ static void run_state_machine(struct tcpm_port *port)
> PD_T_PS_SOURCE_OFF);
> break;
> case PR_SWAP_SNK_SRC_SOURCE_ON:
> + tcpm_enable_auto_vbus_discharge(port, true);
> tcpm_set_cc(port, tcpm_rp_cc(port));
> tcpm_set_vbus(port, true);
> /*
> diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
> index 42fcfbe10590..bffc8d3e14ad 100644
> --- a/include/linux/usb/tcpm.h
> +++ b/include/linux/usb/tcpm.h
> @@ -66,6 +66,8 @@ enum tcpm_transmit_type {
> * For example, some tcpcs may include BC1.2 charger detection
> * and use that in this case.
> * @set_cc: Called to set value of CC pins
> + * @apply_rc: Optional; Needed to move TCPCI based chipset to APPLY_RC state
> + * as stated by the TCPCI specification.
> * @get_cc: Called to read current CC pin values
> * @set_polarity:
> * Called to set polarity
> @@ -120,6 +122,8 @@ struct tcpc_dev {
> int (*get_vbus)(struct tcpc_dev *dev);
> int (*get_current_limit)(struct tcpc_dev *dev);
> int (*set_cc)(struct tcpc_dev *dev, enum typec_cc_status cc);
> + int (*apply_rc)(struct tcpc_dev *dev, enum typec_cc_status cc,
> + enum typec_cc_polarity polarity);
> int (*get_cc)(struct tcpc_dev *dev, enum typec_cc_status *cc1,
> enum typec_cc_status *cc2);
> int (*set_polarity)(struct tcpc_dev *dev,
>

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