usb: typec: tcpm: Implement enabling Auto Discharge disconnect support

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>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20201029063138.1429760-8-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 15 insertions, 0 deletions

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;