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Subject[PATCH v6 12/14] usb: typec: tcpm: Implement enabling Auto Discharge disconnect support
From
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@google.com>
---
Changes since v1:
- Changing patch version to v6 to fix version number confusion.
---
drivers/usb/typec/tcpm/tcpm.c | 74 +++++++++++++++++++++++++++++++++--
include/linux/usb/tcpm.h | 16 ++++++++
2 files changed, 86 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 083e7af107b2..7aca769727d8 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -1694,6 +1694,25 @@ 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_role port_role,
+ 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, port_role, mode, pps_active,
+ requested_vbus_voltage);
+ tcpm_log_force(port,
+ "set_auto_vbus_discharge_threshold pwr_role:%s mode:%d pps_active:%c vbus:%u ret:%d",
+ port_role == TYPEC_SINK ? "sink" : "source", 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)
{
@@ -1863,6 +1882,10 @@ 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_SINK,
+ TYPEC_PWR_MODE_PD,
+ port->pps_data.active,
+ port->supply_voltage);
tcpm_set_state(port, SNK_READY, 0);
} else {
/*
@@ -2777,8 +2800,14 @@ 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) {
+ tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_SOURCE, 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_SOURCE, tcpm_data_role_for_sink(port));
if (ret < 0)
return ret;

@@ -2845,6 +2874,12 @@ 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;
@@ -2909,8 +2944,14 @@ 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_SINK, 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;

@@ -3470,6 +3511,8 @@ static void run_state_machine(struct tcpm_port *port)
* drive VBUS to vSafe0V as shown in Figure 7-9.
*/
tcpm_set_vconn(port, false);
+ tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_SOURCE, TYPEC_PWR_MODE_USB,
+ false, 0);
tcpm_set_vbus(port, false);
tcpm_set_roles(port, port->self_powered, TYPEC_SOURCE,
tcpm_data_role_for_source(port));
@@ -3491,9 +3534,13 @@ static void run_state_machine(struct tcpm_port *port)
tcpm_set_vbus(port, true);
port->tcpc->set_pd_rx(port->tcpc, true);
tcpm_set_attached_state(port, true);
+ tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_SOURCE, TYPEC_PWR_MODE_USB,
+ false, VSAFE5V);
tcpm_set_state(port, SRC_UNATTACHED, PD_T_PS_SOURCE_ON);
break;
case SNK_HARD_RESET_SINK_OFF:
+ tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_SINK, TYPEC_PWR_MODE_USB, false,
+ 0);
memset(&port->pps_data, 0, sizeof(port->pps_data));
tcpm_set_vconn(port, false);
if (port->pd_capable)
@@ -3536,6 +3583,8 @@ 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_SINK, TYPEC_PWR_MODE_USB, false,
+ VSAFE5V);
tcpm_set_state(port, SNK_STARTUP, 0);
break;

@@ -3637,6 +3686,12 @@ 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_auto_vbus_discharge_threshold(port, TYPEC_SOURCE, TYPEC_PWR_MODE_USB,
+ port->pps_data.active, 0);
tcpm_set_vbus(port, false);
port->explicit_contract = false;
/* allow time for Vbus discharge, must be < tSrcSwapStdby */
@@ -3665,9 +3720,18 @@ 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_SINK, 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_SINK, 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);
@@ -3693,6 +3757,8 @@ static void run_state_machine(struct tcpm_port *port)
*/
tcpm_set_pwr_role(port, TYPEC_SOURCE);
tcpm_pd_send_control(port, PD_CTRL_PS_RDY);
+ tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_SOURCE, TYPEC_PWR_MODE_USB,
+ false, VSAFE5V);
tcpm_set_state(port, SRC_STARTUP, PD_T_SWAP_SRC_START);
break;

diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
index 09762d26fa0c..a1707def51c3 100644
--- a/include/linux/usb/tcpm.h
+++ b/include/linux/usb/tcpm.h
@@ -83,6 +83,18 @@ enum tcpm_transmit_type {
* Optional; Called to enable/disable PD 3.0 fast role swap.
* Enabling frs is accessory dependent as not all PD3.0
* accessories support fast role swap.
+ * @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;
@@ -109,6 +121,10 @@ struct tcpc_dev {
const struct pd_message *msg);
int (*set_bist_data)(struct tcpc_dev *dev, bool on);
int (*enable_frs)(struct tcpc_dev *dev, bool enable);
+ int (*enable_auto_vbus_discharge)(struct tcpc_dev *dev, bool enable);
+ int (*set_auto_vbus_discharge_threshold)(struct tcpc_dev *dev, enum typec_role port_role,
+ enum typec_pwr_opmode mode, bool pps_active,
+ u32 requested_vbus_voltage);
};

struct tcpm_port;
--
2.28.0.402.g5ffc5be6b7-goog
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