On Wed, Oct 07, 2020 at 11:15:54PM -0700, Badhri Jagan Sridharan wrote:
> TCPCI spec allows TCPC hardware to autonomously discharge the vbus
> capacitance upon disconnect. The expectation is that the TCPM enables
> AutoDischargeDisconnect while entering SNK/SRC_ATTACHED states. Hardware
> then automously discharges vbus when the vbus falls below a certain
> threshold i.e. VBUS_SINK_DISCONNECT_THRESHOLD.
>
> Apart from enabling the vbus discharge circuit, AutoDischargeDisconnect
> is also used a flag to move TCPCI based TCPC implementations into
> Attached.Snk/Attached.Src state as mentioned in
> Figure 4-15. TCPC State Diagram before a Connection of the
> USB Type-C Port Controller Interface Specification.
> In such TCPC implementations, setting AutoDischargeDisconnect would
> prevent TCPC into entering "Connection_Invalid" state as well.
>
> Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> Changes since v1:
> - Changing patch version to v6 to fix version number confusion.
>
> Changes since v6:
> - Fixed incorrect data_role error that I introduced by mistake in
> the previous version.
>
> Changes since v7:
> - Rebase on usb-next
>
> Changes since v8:
> - Removing the call to tcpm_set_auto_vbus_discharge_threshold
> in the source path.
>
> - Changes since v9:
> - None
> ---
> drivers/usb/typec/tcpm/tcpm.c | 60 ++++++++++++++++++++++++++++++++---
> include/linux/usb/tcpm.h | 15 +++++++++
> 2 files changed, 71 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index d5a3e2b3bea2..51a14d282109 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -1701,6 +1701,24 @@ static void tcpm_handle_alert(struct tcpm_port *port, const __le32 *payload,
> }
> }
>
> +static int tcpm_set_auto_vbus_discharge_threshold(struct tcpm_port *port,
> + enum typec_pwr_opmode mode, bool pps_active,
> + u32 requested_vbus_voltage)
> +{
> + int ret;
> +
> + if (!port->tcpc->set_auto_vbus_discharge_threshold)
> + return 0;
> +
> + ret = port->tcpc->set_auto_vbus_discharge_threshold(port->tcpc, mode, pps_active,
> + requested_vbus_voltage);
> + tcpm_log_force(port,
> + "set_auto_vbus_discharge_threshold mode:%d pps_active:%c vbus:%u ret:%d",
> + mode, pps_active ? 'y' : 'n', requested_vbus_voltage, ret);
> +
> + return ret;
> +}
> +
> static void tcpm_pd_data_request(struct tcpm_port *port,
> const struct pd_message *msg)
> {
> @@ -1871,6 +1889,10 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> port->current_limit,
> port->supply_voltage);
> port->explicit_contract = true;
> + 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);
> } else {
> /*
> @@ -2785,8 +2807,12 @@ static int tcpm_src_attach(struct tcpm_port *port)
> if (ret < 0)
> return ret;
>
> - ret = tcpm_set_roles(port, true, TYPEC_SOURCE,
> - tcpm_data_role_for_source(port));
> + if (port->tcpc->enable_auto_vbus_discharge) {
> + ret = port->tcpc->enable_auto_vbus_discharge(port->tcpc, true);
> + tcpm_log_force(port, "enable vbus discharge ret:%d", ret);
> + }
> +
> + ret = tcpm_set_roles(port, true, TYPEC_SOURCE, tcpm_data_role_for_source(port));
> if (ret < 0)
> return ret;
>
> @@ -2853,6 +2879,12 @@ static void tcpm_unregister_altmodes(struct tcpm_port *port)
>
> static void tcpm_reset_port(struct tcpm_port *port)
> {
> + int ret;
> +
> + if (port->tcpc->enable_auto_vbus_discharge) {
> + ret = port->tcpc->enable_auto_vbus_discharge(port->tcpc, false);
> + tcpm_log_force(port, "Disable vbus discharge ret:%d", ret);
> + }
> tcpm_unregister_altmodes(port);
> tcpm_typec_disconnect(port);
> port->attached = false;
> @@ -2917,8 +2949,13 @@ static int tcpm_snk_attach(struct tcpm_port *port)
> if (ret < 0)
> return ret;
>
> - ret = tcpm_set_roles(port, true, TYPEC_SINK,
> - tcpm_data_role_for_sink(port));
> + if (port->tcpc->enable_auto_vbus_discharge) {
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, VSAFE5V);
> + ret = port->tcpc->enable_auto_vbus_discharge(port->tcpc, true);
> + tcpm_log_force(port, "enable vbus discharge ret:%d", ret);
> + }
> +
> + ret = tcpm_set_roles(port, true, TYPEC_SINK, tcpm_data_role_for_sink(port));
> if (ret < 0)
> return ret;
>
> @@ -3502,6 +3539,8 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_set_state(port, SRC_UNATTACHED, PD_T_PS_SOURCE_ON);
> break;
> case SNK_HARD_RESET_SINK_OFF:
> + /* Do not discharge/disconnect during hard reseet */
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, 0);
> memset(&port->pps_data, 0, sizeof(port->pps_data));
> tcpm_set_vconn(port, false);
> if (port->pd_capable)
> @@ -3544,6 +3583,7 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_set_charge(port, true);
> }
> tcpm_set_attached_state(port, true);
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, VSAFE5V);
> tcpm_set_state(port, SNK_STARTUP, 0);
> break;
>
> @@ -3645,6 +3685,10 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_set_state(port, PR_SWAP_SNK_SRC_SINK_OFF, 0);
> break;
> case PR_SWAP_SRC_SNK_TRANSITION_OFF:
> + /*
> + * Prevent vbus discharge circuit from turning on during PR_SWAP
> + * as this is not a disconnect.
> + */
> tcpm_set_vbus(port, false);
> port->explicit_contract = false;
> /* allow time for Vbus discharge, must be < tSrcSwapStdby */
> @@ -3673,9 +3717,17 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_set_state_cond(port, SNK_UNATTACHED, PD_T_PS_SOURCE_ON);
> break;
> case PR_SWAP_SRC_SNK_SINK_ON:
> + /* 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);
> break;
> case PR_SWAP_SNK_SRC_SINK_OFF:
> + /*
> + * Prevent vbus discharge circuit from turning on during PR_SWAP
> + * as this is not a disconnect.
> + */
> + tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB,
> + port->pps_data.active, 0);
> tcpm_set_charge(port, false);
> tcpm_set_state(port, hard_reset_state(port),
> PD_T_PS_SOURCE_OFF);
> diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
> index 7303f518ba49..e68aaa12886f 100644
> --- a/include/linux/usb/tcpm.h
> +++ b/include/linux/usb/tcpm.h
> @@ -86,6 +86,18 @@ enum tcpm_transmit_type {
> * @frs_sourcing_vbus:
> * Optional; Called to notify that vbus is now being sourced.
> * Low level drivers can perform chip specific operations, if any.
> + * @enable_auto_vbus_discharge:
> + * Optional; TCPCI spec based TCPC implementations can optionally
> + * support hardware to autonomously dischrge vbus upon disconnecting
> + * as sink or source. TCPM signals TCPC to enable the mechanism upon
> + * entering connected state and signals disabling upon disconnect.
> + * @set_auto_vbus_discharge_threshold:
> + * Mandatory when enable_auto_vbus_discharge is implemented. TCPM
> + * calls this function to allow lower levels drivers to program the
> + * vbus threshold voltage below which the vbus discharge circuit
> + * will be turned on. requested_vbus_voltage is set to 0 when vbus
> + * is going to disappear knowingly i.e. during PR_SWAP and
> + * HARD_RESET etc.
> */
> struct tcpc_dev {
> struct fwnode_handle *fwnode;
> @@ -113,6 +125,9 @@ struct tcpc_dev {
> int (*set_bist_data)(struct tcpc_dev *dev, bool on);
> int (*enable_frs)(struct tcpc_dev *dev, bool enable);
> void (*frs_sourcing_vbus)(struct tcpc_dev *dev);
> + int (*enable_auto_vbus_discharge)(struct tcpc_dev *dev, bool enable);
> + int (*set_auto_vbus_discharge_threshold)(struct tcpc_dev *dev, enum typec_pwr_opmode mode,
> + bool pps_active, u32 requested_vbus_voltage);
> };
>
> struct tcpm_port;
> --
> 2.28.0.806.g8561365e88-goog
--
heikki
