[PATCH 2/2] typec: tcpm: Add option to maintain current limit at Vsafe5V

[Badhri Jagan Sridharan]

During hard reset, TCPM turns off the charging path.
The spec provides an option for Sink to either drop to vSafe5V or vSafe0V.

>From USB_PD_R3_0
2.6.2 Sink Operation
..
Serious errors are handled by Hard Reset Signaling issued by either Port
Partner. A Hard Reset:
resets protocol as for a Soft Reset but also returns the power supply to
USB Default Operation (vSafe0V or vSafe5V output) in order to protect the
Sink.

Add a config option to tcpc_dev and let the device specific driver decide
what needs to be done.

Signed-off-by: Badhri Jagan Sridharan <Badhri@xxxxxxxxxx>
---
 drivers/usb/typec/tcpm.c | 7 ++++++-
 include/linux/usb/tcpm.h | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
index a4e0c027a2a9..350d1a7c4543 100644
--- a/drivers/usb/typec/tcpm.c
+++ b/drivers/usb/typec/tcpm.c
@@ -3269,7 +3269,12 @@ static void run_state_machine(struct tcpm_port *port)
 	case SNK_HARD_RESET_SINK_OFF:
 		memset(&port->pps_data, 0, sizeof(port->pps_data));
 		tcpm_set_vconn(port, false);
-		tcpm_set_charge(port, false);
+		if (port->tcpc->config->vsafe_5v_hard_reset)
+			tcpm_set_current_limit(port,
+					       tcpm_get_current_limit(port),
+					       5000);
+		else
+			tcpm_set_charge(port, false);
 
 		if (port->tcpc->config->self_powered)
 			tcpm_set_roles(port, true, TYPEC_SINK, TYPEC_DEVICE);
diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
index 50c74a77db55..c6e3ccecba70 100644
--- a/include/linux/usb/tcpm.h
+++ b/include/linux/usb/tcpm.h
@@ -90,6 +90,7 @@ struct tcpc_config {
 	enum typec_role default_role;
 	bool try_role_hw;	/* try.{src,snk} implemented in hardware */
 	bool self_powered;	/* port belongs to a self powered device */
+	bool vsafe_5v_hard_reset;	/* Maintain VSAFE5V during hard reset */
 
 	const struct typec_altmode_desc *alt_modes;
 };
-- 
2.19.0.397.gdd90340f6a-goog